Rapid eye movement

Rapid eye movement (REM) sleep is the normal stage of sleep characterized by rapid movements of the eyes. REM sleep is classified into two categories: tonic and phasic. Criteria for REM sleep include not only rapid eye movements, but also low muscle tone and a rapid, low voltage EEG -- these features are easily discernible in a polysomnogram, the sleep study typically done for patients with suspected sleep disorders.

REM sleep in adults typically occupies 20-25% of total sleep, lasting about 90-120 minutes. During a normal night of sleep, we usually experience about 4 or 5 periods of REM sleep; they are quite short at the beginning of the night and longer at the end. It is common to wake for a short time at the end of a REM phase. The relative amount of REM sleep varies considerably with age. A newborn baby spends more than 80% of total sleep time in REM (see also Active Sleep). During REM, the summed activity of the brain's neurons is quite similar to that during waking hours; for this reason, the phenomenon is often called paradoxical sleep. Most of our vividly recalled dreams occur during REM sleep. This also means that there are no dominating brain waves during REM sleep.

REM sleep is so physiologically different[citation needed] from the other phases of sleep that the others are collectively referred to as non-REM sleep.

Physiologically, certain neurons in the brain stem, known as REM sleep-on cells (located in the pontine tegmentum), are particularly active during REM sleep, and are probably responsible for its occurrence. The release of certain neurotransmitters, the monoamines (norepinephrine, serotonin and histamine), is completely shut down during REM. This causes REM atonia, a state in which the motor neurons are not stimulated and thus the body's muscles don't move. Lack of such REM atonia causes REM Behavior Disorder; sufferers act out the movements occurring in their dreams.

Heart rate and breathing rate are irregular during REM sleep, again similar to the waking hours. Body temperature is not well regulated during REM. Erections of the penis (Nocturnal Penile Tumescence or NPT) is an established accompaniment of REM sleep and is used diagnostically to determine if male erectile dysfunction is of organic or psychological origin. Clitoral enlargement, with accompanying vaginal blood flow and transudation (i.e. lubrication) is also present during REM.

The eye movements associated with REM are generated by the pontine nucleus with projections to the superior colliculus and are associated with PGO (pons, geniculate, occipital) waves.


REM sleep disorders
M sleep can occur within about 90 minutes, but in those with a sleep onset REM period, it may be as little as 15-25 minutes. This is considered a sign of narcolepsy.


Theories about the function(s) of REM sleep
The function of REM sleep is not well understood; several theories have been advanced.
According to one theory, certain memories are consolidated during REM sleep. Numerous studies have suggested that REM sleep is important for consolidation of procedural and spatial memories. (Slow-wave sleep, part of non-REM sleep, appears to be important for declarative memories.) However, in people that have no REM sleep (because of brain damage), memory functions are not measurably affected.

Another theory suggests that monoamine shutdown is required so that the monoamine receptors in the brain can recover to regain full sensitivity. Indeed, if REM sleep is repeatedly interrupted, the person will "make up" for it with longer REM sleep at the next opportunity. Acute REM sleep deprivation can improve certain types of depression, and depression appears to be related to an imbalance of certain neurotransmitters. Most antidepressants selectively inhibit REM sleep due to their effects on monoamines. However, this effect decreases after long-term use.

According to a third theory, known as the Ontogenetic Hypothesis of REM sleep, this sleep phase (also known as Active Sleep in neonates) is particularly important to the developing brain, possibly because it provides the neural stimulation that newborns need to form mature neural connections and for proper nervous system development. Studies investigating the effects of Active Sleep deprivation have shown that deprivation early in life can result in behavioral problems, permanent sleep disruption, decreased brain mass and result in an abnormal amount of neuronal cell death. REM sleep is necessary for proper central nervous system development. Further supporting this theory is the fact that the amount of REM sleep decreases with age, as well as the data from other species


REM sleep in other animals
REM sleep occurs in all mammals and birds. It appears that the amount of REM sleep per night in a species is closely correlated with the developmental stage of newborns. The platypus for example, whose newborns are completely helpless and undeveloped, has 8 hours of REM sleep per night; in dolphins, whose newborns are almost completely functional at birth, almost no REM sleep exists after birth.


REM sleep suppressants
Various drugs, including alcohol, benzodiazepines, and antidepressants are known to suppress REM sleep.

How Dream works?

Our dreams combine verbal, visual and emotional stimuli into a sometimes broken, nonsensical but often entertaining story line. We can sometimes even solve problems in our sleep. Or can we? Many experts disagree on exactly what the purpose of our dreams might be. Are they strictly random brain impulses, or are our brains actually working through issues from our daily life while we sleep -- as a sort of coping mechanism? Should we even bother to interpret our dreams? Many say yes, that we have a great deal to learn from our dreams.

In this article, we'll talk about the major dream theories, from Freud's view to the hypotheses that claim we can control our dreams. We'll find out what scientists say is happening in our brains when we dream and why we have trouble remembering these night-time story lines. We'll talk about how you can try to control your dreams -- both what you're dreaming about and what you do once you're having the dream. We'll also find out what dream experts say particular scenarios signify. Finding yourself at work naked may not mean at all what you think it does!


Perchance to Dream
For centuries, we've tried to figure out just why our brains play these nightly shows for us. Early civilizations thought dream worlds were real, physical worlds that they could enter only from their dream state. Researchers continue to toss around many theories about dreaming. Those theories essentially fall into two categories:

The idea that dreams are only physiological stimulations
The idea that dreams are psychologically necessary

Dreams: The Theoretical Divide
Physiological theories are based on the idea that we dream in order to exercise various neural connections that some researchers believe affect certain types of learning. Psychological theories are based on the idea that dreaming allows us to sort through problems, events of the day or things that are requiring a lot of our attention. Some of these theorists think dreams might be prophetic. Many researchers and scientists also believe that perhaps it is a combination of the two theories. In the next section, we'll look at some of the major dream theorists and what they say about why we dream.

Dream Theories
First and foremost in dream theory is Sigmund Freud. Falling into the psychological camp, Dr. Freud's theories are based on the idea of repressed longing -- the desires that we aren't able to express in a social setting. Dreams allow the unconscious mind to act out those unacceptable thoughts and desires. For this reason, his theory about dreams focuses primarily on sexual desires and symbolism. For example, any cylindrical object in a dream represents the penis, while a cave or an enclosed object with an opening represents the vagina. Therefore, to dream of a train entering a tunnel would represent sexual intercourse. According to Freud, this dream indicates a suppressed longing for sex. Freud lived during the sexually repressed Victorian era, which in some way explains his focus. Still, he did once comment that, "Sometimes, a cigar is just a cigar."

Carl Jung studied under Freud but soon decided his own ideas differed from Freud's to the extent that he needed to go in his own direction. He agreed with the psychological origin of dreams, but rather than saying that dreams originated from our primal needs and repressed wishes, he felt that dreams allowed us to reflect on our waking selves and solve our problems or think through issues.

More recently, around 1973, researchers Allan Hobson and Robert McCarley set forth another theory that threw out the old psychoanalytical ideas. Their research on what was going in the brain during sleep gave them the idea that dreams were simply the result of random electrical brain impulses that pulled imagery from traces of experience stored in the memory. They hypothesize that these images don't form the stories that we remember as our dreams. Instead, our waking minds, in trying to make sense of the imagery, create the stories without our even realizing it -- simply because the brain wants to make sense of what it has experienced. While this theory, known as the activation-synthesis hypothesis, created a big rift in the dream research arena because of its leap away from the accepted theories, it has withstood the test of time and is still one of the more prominent dream theories.

Dreaming and the Brain
When we sleep, we go through five sleep stages. The first stage is a very light sleep from which it is easy to wake up. The second stage moves into a slightly deeper sleep, and stages three and four represent our deepest sleep. Our brain activity throughout these stages is gradually slowing down so that by deep sleep, we experience nothing but delta brain waves -- the slowest brain waves (see "Brain Waves" sidebar). About 90 minutes after we go to sleep and after the fourth sleep stage, we begin REM sleep.

Rapid eye movement (REM) was discovered in 1953 by University of Chicago researchers Eugene Aserinsky, a graduate student in physiology, and Nathaniel Kleitman, Ph.D., chair of physiology. REM sleep is primarily characterized by movements of the eyes and is the fifth stage of sleep.

Brain Waves
Our brains cycle through four types of brain waves, referred to as delta, theta, alpha and beta. Each type of brain wave represents a different speed of oscillating electrical voltages in the brain. Delta is the slowest (zero to four cycles per second) and is present in deep sleep. Theta (four to seven cycles per second) is present in stage one when we're in light sleep. Alpha waves, operating at eight to 13 cycles per second, occur during REM sleep (as well as when we are awake). And beta waves, which represent the fastest cycles at 13 to 40 per second, are usually only seen in very stressful situations or situations that require very strong mental concentration and focus. These four brain waves make up the electroencephalogram (EEG).

During REM sleep, several physiological changes also take place. The heart rate and breathing quickens, the blood pressure rises, we can't regulate our body temperature as well and our brain activity increases to the same level (alpha) as when we are awake, or even higher. The rest of the body, however, is essentially paralyzed until we leave REM sleep. This paralysis is caused by the release of glycine, an amino acid, from the brain stem onto the motoneurons (neurons that conduct impulses outward from the brain or spinal cord). Because REM sleep is the sleep stage at which most dreaming takes place, this paralysis could be nature's way of making sure we don't act out our dreams. Otherwise, if you're sleeping next to someone who is dreaming about playing kickball, you might get kicked repeatedly while you sleep.

The four stages outside of REM sleep are called non-REM sleep (NREM). Although most dreams do take place during REM sleep, more recent research has shown that dreams can occur during any of the sleep stages. Tore A. Nielsen, Ph.D., of the Dream and Nightmare Laboratory in Montreal, refers to this as "covert REM sleep" making an appearance during NREM sleep. Most NREM dreams, however, don't have the intensity of REM dreams.

Throughout the night, we go through these five stages several times. Each subsequent cycle, however, includes more REM sleep and less deep sleep (stage three and four). By morning, we're having almost all stage one, two and five (REM) sleep.

Let's look at what happens if you don't get any REM sleep.


Dream Recall
It is said that five minutes after the end of a dream, we have forgotten 50 percent of the dream's content. Ten minutes later, we've forgotten 90 percent of its content. Why is that? We don't forget our daily actions that quickly. The fact that they are so hard to remember makes their importance seem less.

Freud theorized that we forget our dreams because they contain our repressed thoughts and wishes and so we shouldn't want to remember them anyway. Other research points to the simple reason that other things get in the way. We are forward-thinking by nature, so remembering something when we first wake up is difficult.

L. Strumpell, a dream researcher of the same era as Freud, believed that several things contribute to our not being able to remember dreams. For one, he said that many things are quickly forgotten when you first wake up, such as physical sensations. He also considered the fact that many dream images are not very intense and would therefore be easy to forget. Another reason, and probably the strongest of his theories, is that we traditionally learn and remember both by association and repetition. As dreams are usually unique and somewhat vague to begin with, it stands to reason that remembering them could be difficult. For example, if someone speaks a phrase to you that doesn't immediately click with anything in your experience, you might need the person to repeat it in order to remember it or even understand it. Since we can't go back to our dreams to experience something again, details that are out of our realm of experience often escape us.

How to Improve Your Dream Recall
There are many resources both on the Web and in print that will give you tips on how to improve your recall of dreams. Those who believe we have a lot to learn about ourselves from our dreams are big proponents of dream journals. Here are some steps you can take to increase your dream recall:

When you go to bed, tell yourself you will remember your dreams. (Author's note: In researching this article, I found that thinking about dreams before I fell asleep actually made me remember having them, so this step did work in my experience.)
Set your alarm to go off every hour and half so you'll wake up around the times that you leave REM sleep -- when you're most likely to remember your dreams. (Or, drink a lot of water before you go to bed to ensure you have to wake up at least once in the middle of the night!)

Keep a pad and pencil next to your bed.
Try to wake up slowly to remain within the "mood" of your last dream.


Controlling Dreams
Lucid Dreaming
There is a lot of research being done in dream control, particularly in the areas of lucid dreaming and dream incubation. Lucid dreaming is a learned skill and occurs when you are dreaming, you realize you are dreaming and you are able to then control what happens in your dream -- all while you're still asleep.

Being able to control your dreams would be a very cool thing to be able to do, but it is a difficult skill that usually takes special training. It is estimated that fewer than 100,000 people in the United States have the ability to have lucid dreams.

Although lucid dreaming is mentioned throughout history, it was not until 1959 at Johann Wolfgang Goethe University that an effective technique for inducing lucid dreams was developed, and true research into the phenomenon began taking place. In 1989, Paul Tholey, a German dream researcher who had been involved in the research at that university, wrote a paper about a technique he was studying to induce lucid dreams. It was called the reflection technique, and it involved asking yourself throughout the day if you were awake or dreaming. More research has indicated the need to practice recognizing odd occurrences, or dream signs, that would be a sign that "this is a dream" rather than reality.

Stephen LaBerge of Stanford University, founder of The Lucidity Institute, Lynne Levitan and other current dream researchers have studied lucid dreaming techniques extensively. They refer to a technique similar to Tholey's reflection method that they call "reality testing." This technique and one called MILD (Mnemonic Induction of Lucid Dreams) have been among the most successful techniques for lucid dreaming.

The MILD technique involves similar reminders to the reality testing method but focuses those reminders at night rather than throughout the day and night. MILD begins with telling yourself when you go to bed that you'll remember your dreams. You then focus your attention on recognizing when you are dreaming and remembering that it is a dream. Then, you focus on reentering a recent dream and looking for clues that it is indeed a dream. You imagine what you would like to do within that dream. For example, you may want to fly, so you imagine yourself flying within that dream. You repeat these last two steps (recognizing when you're dreaming and reentering a dream) until you go to sleep. Using this technique, Dr. LaBerge has been able to have lucid dreams at will. Because this type of technique takes such mental training, however, LaBerge is now doing research using external stimuli to induce lucid dreams.

While lucid dreaming may just seem like a cool way to enter fantasy land, it also has several applications outside of recreation. According to LaBerge, for instance, lucid dreaming can help in personal development, enhancing self-confidence, overcoming nightmares, improving mental (and perhaps physical) health and facilitating creative problem solving. LaBerge also states on the Lucidity Web site:

Lucid dreaming could provide the handicapped and other disadvantaged people with the nearest thing to fulfilling their impossible dreams: paralytics could walk again in their dreams, to say nothing of dancing and flying, and even experience emotionally satisfying erotic fantasies. Such sensorimotor practice could conceivably facilitate recovery from stroke.

Finally, lucid dreaming can function as a "world simulator." Just as a flight simulator allows people to learn to fly in a safe environment, lucid dreaming could allow people to learn to live in any imaginable world; to experience and better choose among various possible futures.

Dream Incubation
Dream incubation is learning to plant a seed for a specific dream topic to occur. For example, you might go to bed repeating to yourself that you'll dream about a presentation you have coming up or a vacation you just took. Those who believe in problem solving through dreams use this technique to direct their dreams to the specific topic.

While somewhat similar to lucid dreaming in that problems can be solved, dream incubation is simply focusing attention on a specific issue when going to sleep. Several studies have shown this method to be successful over a period of time. For example, in a study at Harvard Medical School, Dr. Diedre Barrett had her students focus on a problem before going to sleep and found that it was certainly possible to come up with novel solutions in dreams that are both personally satisfying and reasonable to an outside observer. In her studies, two-thirds of participants had dreams that addressed their chosen problem, while one-third actually came up with solutions in their dreams.


What do our dreams mean?
Those on the physiology side of the "why we dream" argument see dreams as only nonsense that the brain creates from fragments of images and memory. For centuries, however, people have looked at their dreams as both omens and insights into their own psyches. Many think dreams are full of symbolic messages that may not be clear to us on the surface. But, if we dig deeper and think about what is going on in our lives, we can usually come up with an interpretation that makes sense. Let's look at the most common dream themes and how dream experts interpret them.
Common Dream Themes and Their Interpretations

Being naked in public
Most of us have had the dream at some point that we're at school, work or some social event, and we suddenly realize we forgot to put on clothes! Experts say this means:
We're trying to hide something (and without clothes we have a hard time doing that).
We're not prepared for something, like a presentation or test (and now everyone is going to know -- we're exposed!).
If we're naked but no one notices, then the interpretation is that whatever we're afraid of is unfounded. If we don't care that we're naked, the interpretation is that we're comfortable with who we are.

Falling
You're falling, falling, falling... and then you wake up. This is a very common dream and is said to symbolize insecurities and anxiety. Something in your life is essentially out of control and there is nothing you can do to stop it. Another interpretation is that you have a sense of failure about something. Maybe you're not doing well in school or at work and are afraid you're going to be fired or expelled. Again, you feel that you can't control the situation.

Being chased
The ever-popular chase dream can be extremely frightening. What it usually symbolizes is that you're running away from your problems. What that problem is depends on who is chasing you. It may be a problem at work, or it may be something about yourself that you know is destructive. For example, you may be drinking too much, and your dream may be telling you that your drinking is becoming a real problem.

Taking an exam (or forgetting that you have one)
This is another very common dream. You suddenly realize you are supposed to be taking an exam at that very moment. You might be running through the hallways and can't find the classroom. This type of dream can have several variations that have similar meanings. (Maybe your pen won't write, so you can't finish writing your answers.) What experts say this may mean is that you're being scrutinized about something or feel you're being tested -- maybe you're facing a challenge you don't think you're up to. You don't feel prepared or able to hold up to the scrutiny. It may also mean there is something you've neglected that you know needs your attention.

Flying
Many flying dreams are the result of lucid dreaming. Not all flying dreams are, however. Typically, dreaming that you are flying means you are on top of things. You are in control of the things that matter to you. Or, maybe you've just gained a new perspective on things. It may also mean you are strong willed and feel like no one and nothing can defeat you. If you are having problems maintaining your flight, someone or something may be standing in the way of you having control. If you are afraid while flying, you may have challenges that you don't feel up to.

Running, but going nowhere
This theme can also be part of the chasing dream. You're trying to run, but either your legs won't move or you simply aren't going anywhere -- as if you were on a treadmill. According to some, this dream means you have too much on your plate. You're trying to do too many things at once and can't catch up or ever get ahead.

Your teeth falling out
Many people have dreams that they lose all of their teeth. In this dream, they may feel something strange in their mouth and then spit teeth into their hand, eventually losing all of their teeth. According to some, our teeth are related to our sense of power and our ability to communicate. Losing our teeth not only makes us embarrassed by our appearance, which hinders our communications, but it also lessens our power because we may not speak our minds. It's also associated with feelings about our appearance.


Recurring Dreams and Nightmares
Many people have the same or a similar dream many times, over either a short period of time or their lifetime. Recurring dreams usually mean there is something in your life you've not acknowledged that is causing stress of some sort. The dream repeats because you have not corrected the problem. Another theory is that people who experience recurring dreams have some sort of trauma in their past they are trying to deal with. In this case, the dreams tend to lessen with time.

Nightmares are dreams that are so distressing they usually wake us up, at least partially. Nightmares can occur at any age but are seen in children with the most frequency. Nightmares usually cause strong feelings of fear, sadness or anxiety. Their causes are varied. Some medications cause nightmares (or cause them if you discontinue the medication abruptly). Traumatic events also cause nightmares.

Treatment for recurring nightmares usually starts with interpreting what is going on in the dream and comparing that with what is happening in the person's life. Then, the person undergoes counseling to address the problems that are presumably causing the nightmare. Some sleep centers offer nightmare therapy and counseling. Another method of treating nightmares is through lucid dreaming. Through lucid dreaming, the dreamer can confront his or her attacker and, in some cases, end the nightmares.

Night Terrors
Unlike nightmares that occur during REM sleep, night terrors occur during non-REM sleep, usually in the first cycle of the deepest phase of sleep (within the first hour or two of going to bed). Night terrors can last anywhere from five to 20 minutes. People having a night terror are still asleep but may look like they are awake. For example, they may sit up in bed screaming with their eyes wide open. When they actually do wake up, they usually have no memory of the episode (although some people do remember them). Night terrors occur most frequently in children, but adults can also experience them.


Premonitions in Dreams
The science of dreams is obviously not a clear-cut one. While many believe our dreams mean something, there are also many who don't. But what about dreams that have foretold future events? Has this simply been coincidence? Below are some examples of dreams that have reportedly done just that.

In "Lucid Dreaming," Stephen LaBerge reports that a man took his small son camping near a lake in a small valley near their home. He took the son to the water's edge to take a bath but realized he had forgotten the soap. He left the boy standing by the edge of the water and saw him picking up pebbles and throwing them into the water. When he returned with the soap, his son was lying face down in the water, dead. The man awoke and immediately realized this was only a dream. A while after that, some friends invited him and his son to go camping. Although it didn't occur to him immediately, the setting was similar to the setting he had seen in his dream. At one point during the camping trip, he took his son to the lake to take a bath but realized he had forgotten the soap. He sat the boy down and was leaving to get the soap when he saw the boy reach down and pick up pebbles to throw into the water. His dream immediately jumped into his head, and he snatched the boy up and took him with him.

There is an investment group made up of people who have precognitive dreams about stocks. Phenomena Magazine: Precognitive Stock Market Dreamers (November 1, 2004) reports that Dr. Arthur Bernard, a psychologist who teaches dreamwork and a member of the group, had a very successful experience. He had a recurring dream about an obscure biotech stock called ICOS. In the dream, he saw the stock suddenly explode in value. Because of the intensity of the dream, he felt sure that this dream was precognitive. He bought about 40,000 shares of ICOS at $4 per share. He sold his shares in 1998 at $28 each, amounting to an approximate $1.6 million profit.

Science Frontiers Online: Precognitive Dreams (Nov-Dec 1998) reports that M.S. Stowell, in her doctoral dissertation, interviewed several people who claimed to have precognitive dreams. Of 51 presumed precognitive dreams, Stowell was able to prove that 37 had indeed come true. One report from a woman named Elizabeth told of a dream about a plane crashing on a highway near an overpass. Elizabeth was driving her car on that highway at the time and could see that the plane was going to crash there as she drove under the overpass. In her dream, she just escaped the plane. Within a few weeks, a plane crashed on the highway she had dreamt about.

Ongoing Dream Research and Therapy
Research in various areas of dreaming is ongoing, particularly in the areas of REM sleep and lucidity. One study in lucid dreaming involves trying to get the dreamer to communicate with observers while he or she is dreaming. Stephen LaBerge, who is at the forefront of lucid dreaming research, has successfully achieved communication through eye movements, but of course this type of communication is very limited. His ongoing work involves dreamers wearing a glove that incorporates movement sensors to record hand movements during sleep. By using sign language, they hope be able to get reports of dreams as they are occurring.

One day, perhaps we'll all be able to control our dreams or even share our dreams with others while we sleep.

How sleep works?

Everyone sleeps, but any idea how it works?
Sleep is one of those funny things about being a human being -- you just have to do it. Have you ever wondered why? And what about the crazy dreams, like the one where a bad person is chasing you and you can't run or yell.

If you have ever wondered about why people have to sleep or what causes dreams, then read on. In this article, you'll find out all about sleep and what it does for you.

Characteristics of Sleep
We all know how sleep looks -- when we see someone sleeping, we recognize the following characteristics:

If possible, the person will lie down to go to sleep.
- The person's eyes are closed.
- The person doesn't hear anything unless it is a loud noise.
- The person breathes in a slow, rhythmic pattern.
- The person's muscles are completely relaxed. If sitting up, the person may fall out of his or her chair as sleep deepens.

During sleep, the person occasionally rolls over or rearranges his or her body. This happens approximately once or twice an hour. This may be the body's way of making sure that no part of the body or skin has its circulation cut off for too long a period of time.

In addition to these outward signs, the heart slows down and the brain does some pretty funky things.
In other words, a sleeping person is unconscious to most things happening in the environment. The biggest difference between someone who is asleep and someone who has fainted or gone into a coma is the fact that a sleeping person can be aroused if the stimulus is strong enough. If you shake the person, yell loudly or flash a bright light, a sleeping person will wake up.

For any animal living in the wild, it just doesn't seem very smart to design in a mandatory eight-hour period of near-total unconsciousness every day. Yet that is exactly what evolution has done. So there must be a pretty good reason for it!

Reptiles, birds and mammals all sleep. That is, they become unconscious to their surroundings for periods of time. Some fish and amphibians reduce their awareness but do not ever become unconscious like the higher vertebrates do. Insects do not appear to sleep, although they may become inactive in daylight or darkness.

By studying brainwaves, it is known that reptiles do not dream. Birds dream a little. Mammals all dream during sleep.

Different animals sleep in different ways. Some animals, like humans, prefer to sleep in one long session. Other animals (dogs, for example) like to sleep in many short bursts. Some sleep at night, while others sleep during the day.
If you attach an electroencephalograph to a person's head, you can record the person's brainwave activity. An awake and relaxed person generates alpha waves, which are consistent oscillations at about 10 cycles per second. An alert person generates beta waves, which are about twice as fast.

During sleep, two slower patterns called theta waves and delta waves take over. Theta waves have oscillations in the range of 3.5 to 7 cycles per second, and delta waves have oscillations of less than 3.5 cycles per second. As a person falls asleep and sleep deepens, the brainwave patterns slow down. The slower the brainwave patterns, the deeper the sleep -- a person deep in delta wave sleep is hardest to wake up.

At several points during the night, something unexpected happens -- rapid eye movement (REM) sleep occurs. Most people experience three to five intervals of REM sleep per night, and brainwaves during this period speed up to awake levels. If you ever watch a person or a dog experiencing REM sleep, you will see their eyes flickering back and forth rapidly. In many dogs and some people, arms, legs and facial muscles will twitch during REM sleep. Periods of sleep other than REM sleep are know as NREM (non-REM) sleep.

REM sleep is when you dream. If you wake up a person during REM sleep, the person can vividly recall dreams. If you wake up a person during NREM sleep, generally the person will not be dreaming.

You must have both REM and NREM sleep to get a good night's sleep. A normal person will spend about 25 percent of the night in REM sleep, and the rest in NREM. A REM session -- a dream -- lasts five to 30 minutes.

Medicine can hamper your ability to get a good night's sleep. Many medicines, including most sleeping medicines, change the quality of sleep and the REM component of it.

Missing out on a good night's sleep can seriously affect what happens when you're awake. We'll look at what happens next.

Missing Sleep
One way to understand why we sleep is to look at what happens when we don't get enough:
As you know if you have ever pulled an all-nighter, missing one night of sleep is not fatal. A person will generally be irritable during the next day and will either slow down (become tired easily) or will be totally wired because of adrenalin.
If a person misses two nights of sleep, it gets worse. Concentration is difficult, and attention span falls by the wayside. Mistakes increase.

After three days, a person will start to hallucinate and clear thinking is impossible. With continued wakefulness a person can lose grasp of reality. Rats forced to stay awake continuously will eventually die, proving that sleep is essential.
A person who gets just a few hours of sleep per night can experience many of the same problems over time.
Two other things are known to happen during sleep. Growth hormone in children is secreted during sleep, and chemicals important to the immune system are secreted during sleep. You can become more prone to disease if you don't get enough sleep, and a child's growth can be stunted by sleep deprivation.

But the question remains -- why do we need to sleep? No one really knows, but there are all kinds of theories, including these:

Sleep gives the body a chance to repair muscles and other tissues, replace aging or dead cells, etc.
Sleep gives the brain a chance to organize and archive memories. Dreams are thought by some to be part of this process.
Sleep lowers our energy consumption, so we need three meals a day rather than four or five. Since we can't do anything in the dark anyway, we might as well "turn off" and save the energy.

According to ScienceNewsOnline: Napless cats awaken interest in adenosine, sleep may be a way of recharging the brain, using adenosine as a signal that the brain needs to rest: "Since adenosine secretion reflects brain cell activity, rising concentrations of this chemical may be how the organ gauges that it has been burning up its energy reserves and needs to shut down for a while." Adenosine levels in the brain rise during wakefulness and decline during sleep.

What we all know is that, with a good night's sleep, everything looks and feels better in the morning. Both the brain and the body are refreshed and ready for a new day.

Dreams and Improving Sleep Habits
Why do we have such crazy, kooky dreams? Why do we dream at all for that matter? According to Joel Achenbach in his book

Why Things Are:
The brain creates dreams through random electrical activity. Random is the key word here. About every 90 minutes the brain stem sends electrical impulses throughout the brain, in no particular order or fashion. The analytic portion of the brain -- the forebrain -- then desperately tries to make sense of these signals. It is like looking at a Rorschach test, a random splash of ink on paper. The only way of comprehending it is by viewing the dream (or the inkblot) metaphorically, symbolically, since there's no literal message.

This doesn't mean that dreams are meaningless or should be ignored. How our forebrains choose to "analyze" the random and discontinuous images may tell us something about ourselves, just as what we see in an inkblot can be revelatory. And perhaps there is a purpose to the craziness: Our minds may be working on deep-seated problems through these circuitous and less threatening metaphorical dreams.

Here are some other things you may have noticed about your dreams:
Dreams tell a story. They are like a TV show, with scenes, characters and props.
Dreams are egocentric. They almost always involve you.
Dreams incorporate things that have happened to you recently. They can also incorporate deep wishes and fears.
A noise in the environment is often worked in to a dream in some way, giving some credibility to the idea that dreams are simply the brain's response to random impulses.

You usually cannot control a dream -- in fact, many dreams emphasize your lack of control by making it impossible to run or yell. (However, proponents of lucid dreaming try to help you gain control.)
Dreaming is important. In sleep experiments where a person is woken up every time he/she enters REM sleep, the person becomes increasingly impatient and uncomfortable over time.


How Much Sleep Do I Need?
Most adult people seem to need seven to nine hours of sleep a night. This is an average, and it is also subjective. You, for example, probably know how much sleep you need in an average night to feel your best.

The amount of sleep you need decreases with age. A newborn baby might sleep 20 hours a day. By age four, the average is 12 hours a day. By age 10, the average falls to 10 hours a day. Senior citizens can often get by with six or seven hours a day.


Tips to Improve Your Sleep
Exercise regularly. Exercise helps tire and relax your body.
Don't consume caffeine after 4:00 p.m. or so. Avoid other stimulants like cigarettes as well.
Avoid alcohol before bedtime. Alcohol disrupts the brain's normal patterns during sleep.
Try to stay in a pattern with a regular bedtime and wakeup time, even on weekends.

Sleep Pattern May Indicate Depression

A particular sleep profile runs in families and that the sleep profile seems to be fairly clearly associated with an increased susceptibility of family members to suffer from depression. Researchers may actually be closer to learning about the genetics of depression by pursuing sleep as a means of what might be underlying depression's development.

Two major sleep states are rapid eye movement (REM) and non-REM. Non-REM is classified by overall brain wave slowing. It occurs in stages 1-4, where 1 is the most activated brain and 4 is the least activated. Deep sleep is low wave, occurring in stages 3-4. REM is when brain activity is similar to when people are awake, but they are really deeply asleep.

The sleep profile the researchers identified is characterized by an earlier onset to this REM state and a drop out in slow wave sleep. Overall, there is more REM sleep and less slow wave sleep and a quicker slide into REM sleep. This discovery led the researchers to conclude that there is a fundamental regulatory problem in sleep which is linked to people's vulnerability for depression.

Relatives of depressed people who have rapid REM onset were four times more likely to also have rapid REM onset, and that their risk of depression was nearly double compared with the relatives of other depressed patients. The study findings also suggest that rapid REM onset indicates a higher risk of depression than having a family member with depression.

Most people are not aware that they may have this sleep profile. It is not associated with waking up often during the evening or not feeling rested in the morning. However, if people have a substantial number of family members who seem to have a problem with depression, that suggests they may have this sleep profile.

American Journal of Psychiatry (1998;155:192-199)

COMMENT: Disturbed sleep patterns are a very powerful indicator of depression. It is the most sensitive clue I have to recognize if I am getting depressed. Cardiovascular aerobic exercise is also one of the most effective treatments for disturbed sleeping patterns. Typically, 30-60 minutes four times a week. Doing this amount of exercise or even more is no guarantee that it will work. I know many depressed individuals who are exercise fanatics. However, it is one simple and inexpensive way to treat this problem.

Secrets to a Good Night's Sleep

If you are having sleep problems, whether you are not able to fall asleep, wake up too often, don't feel well-rested when you wake up in the morning, or simply want to improve the quality and quantity of your sleep, try as many of the following techniques below as possible:

* Emotional Freedom Technique (EFT).
Most people can learn this gentle tapping technique in several minutes.
EFT can help balance your body's bioenergy system and resolve some of the emotional stresses that are contributing to the insomnia at a very deep level. The results are typically long lasting and the improvement is remarkably rapid.

* Listen to white noise or relaxation CDs.
Some people find the sound of white noise or nature sounds, such as the ocean or forest, to be soothing for sleep. An excellent relaxation/meditation option to listen to before bed is the Insight audio CD.

* Avoid before-bed snacks, particularly grains and sugars.
This will raise blood sugar and inhibit sleep. Later, when blood sugar drops too low (hypoglycemia), you might wake up and not be able to fall back asleep.

* Sleep in complete darkness or as close as possible.
If there is even the tiniest bit of light in the room it can disrupt your circadian rhythm and your pineal gland's production of melatonin and seratonin. There also should be as little light in the bathroom as possible if you get up in the middle of the night. Please whatever you do, keep the light off when you go to the bathroom at night. As soon as you turn on that light you will for that night immediately cease all production of the important sleep aid melatonin.

* No TV right before bed. Even better, get the TV out of the bedroom or even out of the house, completely.
It is too stimulating to the brain and it will take longer to fall asleep. Also disruptive of pineal gland function for the same reason as above.

* Wear socks to bed.
Due to the fact that they have the poorest circulation, the feet often feel cold before the rest of the body. A study has shown that this reduces night wakings.

* Read something spiritual or religious.
This will help to relax. Don't read anything stimulating, such as a mystery or suspense novel, as this may have the opposite effect. In addition, if you are really enjoying a suspenseful book, you might wind up unintentionally reading for hours, instead of going to sleep.

* Avoid using loud alarm clocks.
It is very stressful on the body to be awoken suddenly. If you are regularly getting enough sleep, they should be unnecessary.

* Journaling.
If you often lay in bed with your mind racing, it might be helpful keep a journal and write down your thoughts before bed. Personally, I have been doing this for 15 years, but prefer to do it in the morning when my brain is functioning at its peak and my coritsol levels are high.

* Melatonin and its precursors.
If behavioral changes do not work, it may be possible to improve sleep by supplementing with the hormone melatonin. However, I would exercise extreme caution in using it, and only as a last resort, as it is a powerful hormone. Ideally it is best to increase levels naturally with exposure to bright sunlight in the daytime (along with full spectrum fluorescent bulbs in the winter) and absolute complete darkness at night. One should get blackout drapes so no light is coming in from the outside. One can also use one of melatonin's precursors, L-tryptophan or 5-hydroxytryptophan (5-HTP). L-tryptophan is the safest and my preference, but must be obtained by prescription only. However, don't be afraid or intimidated by its prescription status. It is just a simple amino acid.

* Get to bed as early as possible.
Our systems, particularly the adrenals, do a majority of their recharging or recovering during the hours of 11 p.m. and 1 a.m. In addition, your gallbladder dumps toxins during this same period. If you are awake, the toxins back up into the liver which then secondarily back up into your entire system and cause further disruption of your health. Prior to the widespread use of electricity, people would go to bed shortly after sundown, as most animals do, and which nature intended for humans as well.

* Check your bedroom for electro-magnetic fields (EMFs).
These can disrupt the pineal gland and the production of melatonin and seratonin, and may have other negative effects as well. To purchase a gauss meter to measure EMFs try Cutcat at 800-497-9516. They have a model for around $40. One doctor even recommends that people pull their circuit breaker before bed to kill all power in the house (Dr. Herbert Ross, author of "Sleep Disorders").

* Keep the temperature in the bedroom no higher than 70 degrees.
Many people keep their homes and particularly the upstairs bedrooms too hot.

* Eat a high-protein snack several hours before bed.
This can provide the L-tryptophan need to produce melatonin and serotonin.

* Also eat a small piece of fruit.
This can help the tryptophan cross the blood-brain barrier.

* Reduce or avoid as many drugs as possible.
Many medications, both prescription and over-the-counter may have effects on sleep. In most cases, the condition, which caused the drugs to be taken in the first place, can be addressed by following the guidelines elsewhere on this web site.

* Avoid caffeine.
A recent study showed that in some people, caffeine is not metabolized efficiently and therefore they can feel the effects long after consuming it. So an afternoon cup of coffee (or even tea) will keep some people from falling asleep. Also, some medications, particularly diet pills contain caffeine.

* Alarm clocks and other electrical devices.
If these devices must be used, keep them as far away from the bed as possible, preferably at least 3 feet.

* Avoid alcohol.
Although alcohol will make people drowsy, the effect is short lived and people will often wake up several hours later, unable to fall back asleep. Alcohol will also keep you from falling into the deeper stages of sleep, where the body does most of its healing.

* Lose weight.
Being overweight can increase the risk of sleep apnea, which will prevent a restful nights sleep.

* Avoid foods that you may be sensitive to.
This is particularly true for dairy and wheat products, as they may have effect on sleep, such as causing apnea, excess congestion, gastrointestinal upset, and gas, among others.

* Don't drink any fluids within 2 hours of going to bed.
This will reduce the likelihood of needing to get up and go to the bathroom or at least minimize the frequency.

* Take a hot bath, shower or sauna before bed.
When body temperature is raised in the late evening, it will fall at bedtime, facilitating sleep,

* Remove the clock from view.
It will only add to your worry when constantly staring at it... 2 a.m. ...3 a.m. ... 4:30 a.m. ...

* Keep your bed for sleeping.
If you are used to watching TV or doing work in bed, you may find it harder to relax and to think of the bed as a place to sleep.

* Have your adrenals checked by a good natural medicine clinician.
Scientists have found that insomnia may be caused by adrenal stress (Journal of Clinical Endocrinology & Metabolism, August 2001; 86:3787-3794).

* If you are menopausal or perimenopausal, get checked out by a good natural medicine physician.
The hormonal changes at this time may cause problems if not properly addressed.

* Don't change your bedtime.
You should go to bed, and wake up, at the same times each day, even on the weekends. This will help your body to get into a sleep rhythm and make it easier to fall asleep and get up in the morning.

* Make certain you are exercising regularly.
Exercising for at least 30 minutes everyday can help you fall asleep. However, don't exercise too close to bedtime or it may keep you awake. Studies show exercising in the morning is the best if you can do it.

* Establish a bedtime routine.
This could include meditation, deep breathing, using aromatherapy or essential oils or indulging in a massage from your partner. The key is to find something that makes you feel relaxed, then repeat it each night to help you release the day's tensions.

* Go to the bathroom right before bed.
This will reduce the chances that you'll wake up to go in the middle of the night. Wear an eye mask to block out light. As said above, it is very important to sleep in as close to complete darkness as possible. That said, it's not always easy to block out every stream of light using curtains, blinds or drapes, particularly if you live in an urban area (or if your spouse has a different schedule than you do). In these cases, an eye mask can help to block out the remaining light.

* Put your work away at least one hour (but preferably two or more) before bed.
This will give your mind a chance to unwind so you can go to sleep feeling calm, not hyped up or anxious about tomorrow's deadlines.

Get a Good Nights Sleep

Your “sleep hygiene” describes your sleep habits. By improving your sleep habits, you can increase your chance of falling asleep fast, staying asleep and sleeping between seven to nine hours each night. A good night’s sleep has many health benefits. Most importantly, you will feel great.

1) Only Sleep and Have Sex in the Bedroom
The bedroom should be used only for sleep and sex. That means no reading in bed and no TV in bed. Doing these things (or anything else) confuses your body, making it difficult to fall asleep. Give yourself about 15 minutes to fall asleep. If you haven’t fallen asleep by then, get out of bed until you are sleepy. You can do some quiet reading (pick something boring), but avoid TVs and computer screens. Remember, your goal is to train yourself to fall asleep quickly. Reading a stimulating book, watching TV or doing anything else undermines that.


2) Keep a Schedule
Go to bed and wake up at the same time every day. This will train your body to sleep on a schedule. If you can maintain this schedule for several weeks, you will probably find yourself falling asleep faster and feeling more refreshed. Do not sleep in on weekends or stay up late. Your body adjusts to changes in your sleep schedule at a rate of one hour per day. That means if you wake up at 6:30 a.m. on weekdays, but 8:30 a.m. on weekends, you need two days to adjust. You won’t be sleeping well again until Wednesday each week.


3) Make a Bedtime Ritual
Create a nightly ritual to signal that it is time to sleep. Start the ritual about 30 minutes before you lie down to help release stressful thoughts and be ready to sleep when you lie down. A little quiet reading (not in bed) or a warm bath can be great. Avoid watching TV, since it stimulates your brain.


4) Exercise Daily
Daily exercise will improve your chances of falling asleep quickly and sleeping deeply. Try to exercise early in the day and never within three hours of bedtime. Exercising too late in the day can make it difficult for you to fall asleep. A daily exercise habit will not only improve your sleep hygiene, but it will also improve your overall health.


5) Get Some Sunlight
Sunlight helps regulate your circadian clock and make you feel sleepy at night by stimulating your body to produce melatonin (a hormone that regulates your sleep cycle). You need exposure to bright light every day. Morning sunlight exposure can be especially helpful. Be sure to open the drapes every morning to let light in.


6) Avoid Caffeine in the Afternoon
Some people are caffeine sensitive and cannot drink any coffee, tea or other caffeinated beverage up to six hours before bedtime. If you are having trouble sleeping, try avoiding all afternoon and evening caffeine.


7) Make Your Bedroom Dark
The contrast between light during the day and dark at night helps reinforce your body’s natural rhythms. By making your bedroom dark at night, you will be able to fall asleep faster and stay asleep longer. Closing drapes and doors can help reduce the light in your bedroom.


8) Avoid Alcohol
That small glass of wine can make it more difficult to stay asleep. After an evening drink, you might fall asleep just fine, but you will likely wake up in the middle of the night. This effect is caused by a rebound in blood sugar and withdrawal from the alcohol after it is metabolized. Try avoiding alcohol before sleep and see if you sleep more soundly. For every drink you have, give your body at least an hour to process it before trying to fall asleep.


9) Don't Smoke
The nicotine in cigarettes is a stimulant that will keep you awake, which is just one of the things that smoking does to your body. If you smoke, many resources are available to help you quit. The benefits quitting include better sleep, a longer life, more energy and saving money. Smokers also may wake up early due to nicotine withdrawal.


10) See a Doctor
Finally, if these lifestyle changes don’t help, contact your doctor. You may have a sleep disorder or just may need some temporary help getting yourself in good ‘sleep shape.’

Sleeping Disorder?

How much sleep do you get each night? If you are sleep for less than 7 hours a night, you may be suffering from a lack of sleep. Many people can function on less than 7 hours of sleep, but they are not at their best. Over many weeks or years, this lack of sleep interacts with the body and can worsen health conditions. About 95% of the population needs between 7 and 9 hours of sleep each night. Sure, there are a lucky few who physically need less -- but that is a rare situation. If you are not feeling energetic during the day, add hours to your sleep and see if it makes a difference.

How much sleep we need depends on what is happening in our bodies. The rapid growth of infancy and adolescence and the demands on the body during pregnancy mean more sleep. Contrary to the common sleep myth, older adults need just as much sleep as younger ones. Here is a list of sleep needs by group:

Infants: 16 hours a day
Young Children: 10-14 hours a day
Teenagers: 9 hours a day
Pregnant women: several extra hours a day in the first trimester
Adults: 7 to 9 hours a day
Older Adults: 7 to 9 hours a day
Finding Your 'Sleep Need'

A person should be alert and awake throughout the day. Some signs that you are not getting enough quality sleep include:
- Feeling tired during the day
- Falling asleep within 5 minutes of lying down
- Experiencing “microsleeps” or brief “nodding off” episodes
- Sleep Quality and Sleep Quantity

If you find that you are not getting enough sleep, there are two things to look at: the amount of time you spend sleeping and the quality of your sleep. Sleep Time: If you spend less than 7 hours in bed (asleep) each night, you will most likely have a sleep deficit.

You could also be spending enough time in bed, but have trouble falling asleep quickly. Learning good sleep habits can help you fall asleep faster and get more sleep in the same amount of time. Sleep Quality: If your sleep is interrupted, if you wake up several times a night or if you toss and turn, your sleep quality may be poor. You need two kinds of sleep each night – deep sleep (sleep stage 3 and 4), which makes you feel refreshed, and REM sleep, which we don’t fully understand, but we know you need it. Developing better sleep habits can help with sleep quality.

Sleep Disorders and Problems
There are also many types of sleep disorders that can impact your sleep. The two most common sleep disorders are insomnia and sleep apnea. Less common sleep disorders include narcolepsy and restless leg syndrome (RLS). These disorders can be caused by health conditions, medications, anxiety and other factors. Narcolepsy is a rare disease that affects between 25 and 50 people per 100,000 people. RLS is more common. However, several clinical conditions are associated with RLS, such as iron deficiency, chronic kidney diseases, pregnancy, polyneuropathy, type 2 diabetes mellitus and multiple sclerosis. Many sleep disorders can be treated through a combination of changing your sleep habits and medications. Sleep apnea generally requires treatment with positive airway pressure. Many people over 65 have trouble sleeping because of health conditions.


Understanding Sleep
Sleep is a major part of our lives. However, researchers and doctors understand little about sleep and what it does for us. What we do know is that sleep has many health benefits and getting a good night’s sleep is the key to feeling energized every day. Understanding sleep can help you improve your health and may even extend your life.


Sleep Habits
Sleep habits are the key to getting a good night’s sleep. We can either train ourselves to fall asleep quickly every night, or we can train ourselves to lie awake in bed through bad habits. Exercise, caffeine, stress and other factors can influence the quantity and quality of our sleep. Changing your sleep habits can lead to greatly improve sleep quality and quantity.


Sleep Disorders and Sleep Problems
If changing your sleep habits doesn’t help, you may have a sleep disorder.
The most common sleep disorders include:
- Insomnia
- Sleep apnea
- Restless Legs Syndrome
- Narcolepsy


The following situations can interfere with your daily Zzzzs as well:
- Jet lag
- Working the night shift
- Nighttime driving
- Snoring


leep Diagnosis and Treatment
You may have a sleep disorder if it takes you more than 30 minutes to fall asleep each night, you are tired during the day and you do not feel rested. If you think you might have a sleep problem, try these three steps:
Improve Your Sleep Habits: Make big changes in your sleep habits for 2 to 3 weeks to see if you can figure out what is causing you to sleep poorly.

Keep a Sleep Diary: Track your sleep and other behaviors for several days to make connections between your daily activities and your sleep quality.

Find a Sleep Center and Doctor: If your sleep doesn’t improve, take your sleep diary to a sleep center or sleep doctor near you for more testing.
Sleep Needs

Each individual’s sleep need varies. For the majority of adults, the daily sleep need is between 7 and 9 hours. Some people need even more than 9 hours and others need less than 7, but this is rare. If you are awake and alert during the day and feel satisfied with your sleep, then you are getting enough sleep.


Sleep and Aging
There is a myth that people need less sleep as they age. This is simply not true: Older adults need 7 to 9 hours of sleep every night. However, good sleep is harder to get as we age because of health conditions, medications and other reasons. Protecting your sleep as you age will give you more energy and better health.
Sleep Myths

Other sleep myths include misunderstandings about the benefit of sleeping in to “catch up” on sleep, sleep in children, the benefits of napping and more. Clearing up these sleep myths will help you to make better decisions about your daily sleep habits.


Sleep Benefits
While we know that sleep makes us feel refreshed, there are many health and other benefits to a good night’s sleep. These include improving heart health, improving your memory and maybe even preventing cancer. Other benefits include improving your skin and helping you concentrate.


Napping
Napping can be a great way to increase your sleep and improve your energy. Napping has been shown to increase productivity and even protect against heart disease. Napping strategies will help you take effective, short naps and then go back to your day recharged.


Sleep Biology
Sleep is a complicated process consisting of five stages. These stages include falling asleep (stage 1), brain slow-down (stage 2), deep sleep (stages 3 and 4) and rapid eye movement (REM). In each stage, the brain and body act differently. During the night, we cycle through all these stages approximately every 100 minutes.
Circadian Rhythms

Throughout the day the body makes changes in various hormone levels. Some of these changes, known as circadian rhythms, control our wake/sleep cycle. By getting enough exposure to bright light and following other behavioral suggestions, we can work with our circadian rhythms help ourselves fall asleep fast every night.
Dreaming and Sleep

Of course, dreaming is one of the strangest and least understood parts of sleep. Dreams seem to be important in creating memories out of the day’s events and solidifying learning. Dreams can be extremely vivid, interesting and potentially meaningful to the dreamer.



Master Napping
Napping, if done effectively, can revitalize you day in a way that no cup of coffee ever can. If done incorrectly, napping can ruin your night sleep and leave you feeling groggy and more tired. Here are a sample of some napping tips:
- nap for 20 minutes
- use an eye pillow
- don't nap within 3 hours of bedtime
- try to nap in the same place each time


Impaired Sleep Quality And Allergic Rhinitis Linked
Patients with allergic rhinitis, such as that caused by hay fever and other allergies, have more difficulty sleeping and more sleep disorders than those without allergies, according to a report in the September 18 issue of Archives of Internal Medicine, a theme issue on sleep.


The Health Effects of Marijuana
Although legalization activists and many marijuana users believe smoking pot has no negative effects, scientific research indicates that marijuana use can cause many health problems. Marijuana is the most commonly used illicit drug in the United States. When smoked, it begins to effect users almost immediately.


Childhood Obesity and Sleep Apnea
Childhood obesity is on the rise, and along with the obesity comes other problems --- heart disease, type 2 diabetes and high blood pressure. Another problem, long thought to be a disorder of older, overweight males, is sleep apnea. Sleep apnea can cause both physical and mental problems

Stress Management Resources

Understanding Stress & Stress Management

What Stress Is... Definitions

This is a dangerous topic!
There have been many different definitions of what stress is, whether used by psychologists, medics, management consultants or others. There seems to have been something approaching open warfare between competing definitions: Views have been passionately held and aggressively defended.

What complicates this is that intuitively we all feel that we know what stress is, as it is something we have all experienced. A definition should therefore be obvious…except that it is not.


Problems of Definition
One problem with a single definition is that stress is made up of many things: It is a family of related experiences, pathways, responses and outcomes caused by a range of different events or circumstances. Different people experience different aspects and identify with different definitions.

Stress is not necessarily something bad – it all depends on how you take it. The stress of exhilarating, creative successful work is beneficial, while that of failure, humiliation or infection is detrimental. The biochemical effects of stress would be experienced irrespective of whether the situation was positive or negative.

Since then, ideas have moved on. In particular, the harmful biochemical and long-term effects of stress have rarely been observed in positive situations.


The current consensus
Now, the most commonly accepted definition of stress is that stress is a condition or feeling experienced when a person perceives that demands exceed the personal and social resources the individual is able to mobilize.

People feel little stress when they have the time, experience and resources to manage a situation. They feel great stress when they think they can't handle the demands put upon them. Stress is therefore a negative experience. And it is not an inevitable consequence of an event: It depends a lot on people's perceptions of a situation and their real ability to cope with it.

This is the main definition used by this site, although we also recognize that there is an intertwined instinctive stress response to unexpected events. The stress response inside us is therefore part instinct and part to do with the way we think.


What Stress Is - The Underlying Mechanisms...

There are two types of instinctive stress response that are important to how we understand stress and stress management: the short-term “Fight-or-Flight” response and the long-term “General Adaptation Syndrome”. The first is a basic survival instinct, while the second is a long-term effect of exposure to stress.

A third mechanism comes from the way that we think and interpret the situations in which we find ourselves.

Actually, these three mechanisms can be part of the same stress response – we will initially look at them separately, and then show how they can fit together.


“Fight-or-Flight”
Some of the early work on stress established the existence of the well-known fight-or-flight response. His work showed that when an animal experiences a shock or perceives a threat, it quickly releases hormones that help it to survive.

These hormones help us to run faster and fight harder. They increase heart rate and blood pressure, delivering more oxygen and blood sugar to power important muscles. They increase sweating in an effort to cool these muscles, and help them stay efficient. They divert blood away from the skin to the core of our bodies, reducing blood loss if we are damaged. And as well as this, these hormones focus our attention on the threat, to the exclusion of everything else. All of this significantly improves our ability to survive life-threatening events.


Power, but little control...
Unfortunately, this mobilization of the body for survival also has negative consequences. In this state, we are excitable, anxious, jumpy and irritable. This reduces our ability to work effectively with other people.

With trembling and a pounding heart, we can find it difficult to execute precise, controlled skills. And the intensity of our focus on survival interferes with our ability to make fine judgments based on drawing information from many sources. We find ourselves more accident-prone and less able to make good decisions.

It is easy to think that this fight-or-flight, or adrenaline, response is only triggered by obviously life-threatening danger. On the contrary, recent research shows that we experience the fight-or-flight response when simply encountering something unexpected.

The situation does not have to be dramatic: People experience this response when frustrated or interrupted, or when they experience a situation that is new or in some way challenging. This hormonal, fight-or-flight response is a normal part of everyday life and a part of everyday stress, although often with an intensity that is so low that we do not notice it.

There are very few situations in modern working life where this response is useful. Most situations benefit from a calm, rational, controlled and socially sensitive approach. Our Relaxation Techniques section explains a range of good techniques for keeping this fight-or-flight response under control.


The General Adaptation Syndrome and Burnout
Starting with the observation that different diseases and injuries to the body seemed to cause the same symptoms in patients, he identified a general response (the “General Adaptation Syndrome”) with which the body reacts to a major stimulus. While the Fight-or-Flight response works in the very short term, the General Adaptation Syndrome operates in response to longer-term exposure to causes of stress.

When pushed to extremes, animals reacted in three stages:
First, in the Alarm Phase, they reacted to the stressor.
Next, in the Resistance Phase, the resistance to the stressor increased as the animal adapted to, and coped with, it. This phase lasted for as long as the animal could support this heightened resistance.
Finally, once resistance was exhausted, the animal entered the Exhaustion Phase, and resistance declined substantially.
Selye established this with many hundreds of experiments performed on laboratory rats. However, he also quoted research during World War II with bomber pilots. Once they had completed a few missions over enemy territory, these pilots usually settled down and performed well. After many missions, however, pilot fatigue would set in as they began to show “neurotic manifestations”.

In the business environment, this exhaustion is seen in “burnout”. The classic example comes from the Wall Street trading floor: by most people’s standards, life on a trading floor is stressful. Traders learn to adapt to the daily stressors of making big financial decisions, and of winning and losing large sums of money. In many cases, however, these stresses increase and fatigue starts to set in.

At the same time, as traders become successful and earn more and more money, their financial motivation to succeed can diminish. Ultimately, many traders experience burnout. We look at this in more detail in our section on burnout.


Stress and the way we think
Particularly in normal working life, much of our stress is subtle and occurs without obvious threat to survival. Most comes from things like work overload, conflicting priorities, inconsistent values, over-challenging deadlines, conflict with co-workers, unpleasant environments and so on. Not only do these reduce our performance as we divert mental effort into handling them, they can also cause a great deal of unhappiness.

We have already mentioned that the most common currently accepted definition of stress is something that is experienced when a person perceives that “demands exceed the personal and social resources the individual is able to mobilize.”


Stress, a matter of judgment
In becoming stressed, people must therefore make two main judgments: firstly they must feel threatened by the situation, and secondly they must doubt that their capabilities and resources are sufficient to meet the threat.

How stressed someone feels depends on how much damage they think the situation can do them, and how closely their resources meet the demands of the situation. This sense of threat is rarely physical. It may, for example, involve perceived threats to our social standing, to other people’s opinions of us, to our career prospects or to our own deeply held values.

Just as with real threats to our survival, these perceived threats trigger the hormonal fight-or-flight response, with all of its negative consequences.

Building on this, this site offers a variety of approaches to managing stress. The navigation bar in the left hand column offers a range of practical methods for managing these stresses by tackling them at source. It also offers some powerful tools for changing your interpretation of stressful situations, thereby reducing the perception of threat.

Pulling these mechanisms together – the integrated stress response…
So far, we have presented the Fight-or-Flight response, the General Adaptation Syndrome, and our mental responses to stress as separate mechanisms. In fact, they can fit together into one response.

The key to this is that ‘Alarm Phase’ is the same thing as Fight-or-Flight response.

We can therefore see that mental stress triggers the fight-or-flight response, and that if this stress is sustained for a long time, the end result might be exhaustion and burnout.


Stress and Your Health

We've already looked at the survival benefits of the fight-or-flight response, as well as the problems this caused for our performance in work-related situations. We've also seen the negative “burnout” effect of exposure to long-term stress. These effects can also affect your health – either with direct physiological damage to your body, or with harmful behavioral effects.

The behavioral effects of stress
The behavioral effects of an over-stressed lifestyle are easy to explain. When under pressure, some people are more likely to drink heavily or smoke, as a way of getting immediate chemical relief from stress.

Others may have so much work to do that they do not exercise or eat properly. They may cut down on sleep, or may worry so much that they sleep badly. They may get so carried away with work and meeting daily pressures that they do not take time to see the doctor or dentist when they need to. All of these are likely to harm health.

The direct physiological effects of excessive stress are more complex. In some areas they are well understood, while in other areas, they are still subject to debate and further research.

Stress and heart disease
The link between stress and heart disease is well-established. If stress is intense, and stress hormones are not ‘used up’ by physical activity, our raised heart rate and high blood pressure put tension on arteries and cause damage to them. As the body heals this damage, artery walls scar and thicken, which can reduce the supply of blood and oxygen to the heart.

This is where a fight-or-flight response can become lethal: Stress hormones accelerate the heart to increase the blood supply to muscles; however, blood vessels in the heart may have become so narrow that not enough blood reaches the heart to meet these demands. This can cause a heart attack.


Other effects of stress
Stress has been also been found to damage the immune system, which explains why we catch more colds when we are stressed. It may intensify symptoms in diseases that have an autoimmune component, such as rheumatoid arthritis. It also seems to affect headaches and irritable bowel syndrome, and there are now suggestions of links between stress and cancer.

Stress is also associated with mental health problems and, in particular, anxiety and depression. Here the relationship is fairly clear: the negative thinking that is associated with stress also contributes to these.

The direct effects of stress in other areas of health are still under debate. In some areas (for example in the formation of stomach ulcers) diseases traditionally associated with stress are now attributed to other causes.

Regular exercise can reduce your physiological reaction to stress. It also strengthens your heart and increases the blood supply to it, directly affecting your vulnerability to heart disease.

Although this site focuses mainly on stress and work performance, many of the tools and techniques within it will help you manage stresses that would otherwise adversely affect your health. However, if you suspect that you are prone to stress-related illness, or if you are in any doubt about the state of your health, you should consult appropriate medical advice immediately. Keep in mind that stress management is only part of any solution to stress-related illness.


Stress and Your Performance

Short-term negative effects that stress hormones can have on your performance, and how stress can contribute to burnout.


The Positive Effects of Pressure
Sometimes, however, the pressures and demands that may cause stress can be positive in their effect. One example of this is where sportsmen and women flood their bodies with fight-or-flight adrenaline to power an explosive performance. Another example is where deadlines are used to motivate people who seem bored or unmotivated. We will discuss this briefly here, but throughout the rest of this site we see stress as a problem that needs to be solved.


And the Negative...
In most work situations jobs, our stress responses causes our performance to suffer. A calm, rational, controlled and sensitive approach is usually called for in dealing with most difficult problems at work: Our social inter-relationships are just too complex not to be damaged by an aggressive approach, while a passive and withdrawn response to stress means that we can fail to assert our rights when we should.

Before we look further at how to manage stress and our performance, it is important to look at the relationship between pressure and performance in a little more detail, first by looking at the idea of the “Inverted-U”, and second by looking at "Flow". This is the ideal state of concentration and focus that brings excellent performance.


Pressure & Performance – the Inverted U
The relationship between pressure and performance is explained in one of the oldest and most important ideas in stress management, the “Inverted-U” relationship between pressure and performance. The Inverted-U relationship focuses on people’s performance of a task.

The left hand side of the graph is easy to explain for pragmatic reasons. When there is very little pressure on us to carry out an important task, there is little incentive for us to focus energy and attention on it. This is particularly the case when there may be other, more urgent, or more interesting, tasks competing for attention.


Negative Thoughts Crowd Our Minds
We are all aware that we have a limited short-term memory: If you try to memorize a long list of items, you will not be able to remember more than six or eight items unless you use formal memory techniques. Similarly, although we have huge processing power in our brains, we cannot be conscious of more than a few thoughts at any one time. In fact, in a very real way, we have a limited “attentional capacity”.

As we become uncomfortably stressed, distractions, difficulties, anxieties and negative thinking begin to crowd our minds. This is particularly the case where we look at our definition of stress, i.e. that it occurs when a person perceives that “demands exceed the personal and social resources the individual is able to mobilize.” These thoughts compete with performance of the task for our attentional capacity. Concentration suffers, and focus narrows as our brain becomes overloaded.

As shown in the figure, this is something of a slippery slope: the more our brain is overloaded, the more our performance can suffer. The more our performance suffers, the more new distractions, difficulties, anxieties and negative thoughts crowd our minds.

Other research has shown that stress reduces people’s ability to deal with large amounts of information. Both decision-making and creativity are impaired because people are unable to take account of all the information available. This inability accounts for the common observation that highly stressed people will persist in a course of action even when better alternatives are available. It also explains why anxious people perform best when they are put under little additional stress, while calm people may need additional pressure to produce a good performance.

Notes on the research behind the Inverted-U:
While this is an important and useful idea, people’s evaluations of stress and performance are by necessity subjective. This has made it difficult to prove the ‘Inverted-U’ idea formally. Also, for ease of explanation, we show a smooth curve here. In reality, different people have different shaped and positioned inverted-Us at different times and in different circumstances. This is all part of “life’s rich tapestry”.


Entering a State of "Flow"
When you are operating in your “area of best performance”, you are normally able to concentrate, and focus all of your attention on the important task at hand. When you do this without distraction, you often enter what Professor Mihaly Csikszentmihalyi of Chicago University describes as a state of ‘flow’. This involves “being completely involved in an activity for its own sake. The ego falls away. Time flies. Every action, movement, and thought follows inevitably from the previous one, like playing jazz. Your whole being is involved, and you're using your skills to the utmost".

You perform at your best in this state because you are able to focus all of your efforts, resources and abilities on the tasks at hand. While you are sufficiently motivated to resist competing temptations, you are not so stressed that anxieties and distractions interfere with clear thought.

This is an intensely creative, efficient and satisfying state of mind. It is the state of mind in which, for example, the most persuasive speeches are made, the best software is developed, and the most impressive athletic or artistic performances are delivered.


Helping Yourself to Get Into Flow
One of the frustrations of management is that managers can feel that they lose the ‘right’ to these periods of deep concentration when they must be readily available to others, and be able to deal with the constantly changing information, decisions and activities around them. Studies of good managers show that they rarely get more than a few minutes alone without distraction. This alone can be frustrating, and can contribute strongly to managerial stress.

In jobs where concentration is a rare commodity, there are various solutions to creating the periods of flow that sustain good performance. Solutions include working from home, or setting aside parts of the day as quiet periods. Another solution might be to delegate the activities that require the greatest levels of concentration, allowing the manager to concentrate on problems as they arise, serving to create a flow of its own.

One of the key aims of this site is to help you manage stress so that you can enter this state of flow, and deliver truly excellent performance in your career.


Introducing Stress Management...

Our main definition of stress is that stress is a condition or feeling experienced when a person perceives that demands exceed the personal and social resources the individual is able to mobilize.

With this in mind, we can now look at how you can manage all of the stresses that your career will bring.

From our definition, you can see that there are three major approaches that we can use to manage stress:

Action-oriented: In which we seek to confront the problem causing the stress, changing the environment or the situation;

Emotionally-oriented: In which we do not have the power to change the situation, but we can manage stress by changing our interpretation of the situation and the way we feel about it; and

Acceptance-oriented: Where something has happened over which we have no power and no emotional control, and where our focus is on surviving the stress.

Action-oriented approaches - best where you have some control
To be able to take an action-oriented approach, we must have some power in the situation. If we do, then action-oriented approaches are some of the most satisfying and rewarding ways of managing stress. These are techniques that we can use to manage and overcome stressful situations, changing them to our advantage.


The early sections on the navigation bar to the left focus on action-oriented coping. These sections introduce skills that help you to manage your job actively, work well with your boss and co-workers, and change your surroundings to eliminate environmental stress. The Action-oriented sections of this site are:

- Cope with the Stress of Work Overload
- Survive the Stress of Problem Jobs
- Deal With Problem People
- Manage Environmental Stress
- Manage Performance Stress
- Avoid Burnout
- Emotionally-oriented approaches - subtle but effective

If you do not have the power to change a situation, then you may be able to reduce stress by changing the way you look at it, using an emotionally-oriented approach.

Emotionally-oriented approaches are often less attractive than action-oriented approaches in that the stresses can recur time and again; however, they are useful and effective in their place. The section on Reducing Stress With Rational Thinking explains some useful techniques for getting another perspective on difficult situations.

Acceptance-oriented approaches - when there's no valid alternative...
Sometimes, we have so little power in a situation that all we can do to survive it. This is the case, for example, when loved-ones die.

In these situations, often the first stage of coping with the stress is to accept one’s lack of power. The section on Defenses Against Stress looks at building the buffers against stress that help you through these difficult periods. Arguably, the section on Useful Relaxation Techniques also falls into this category.

These different approaches to stress management address our definition of stress in different ways: the action-oriented techniques help us to manage the demands upon us and increase the resources we can mobilize; the emotionally oriented techniques help us to adjust our perceptions of the situation; and the acceptance-oriented techniques help us survive the situations that we genuinely cannot change.


article from mindtools

How to feng shui your bedroom

After numerous shifting the layout of my bedroom, i just couldnt get the "feel" right. Sleeping disorder is my worse nightmare and decided to get some feng shui help. For the past weeks, i've been reading from websites and did some research and hopefully this layout will be my last.

Peace, Harmony, Balance
Fortunately Feng Shui refers to your décor. The most important room in the house, the bedroom where you should be spending at least eight hours very night wrapped in the arms of sleep. Feng shui is a Chinese concept and is a way of creating balance and harmony, not just in the bedroom, but in the entire house and in your life. It's a method of balancing the yin (feminine) and yang (masculine) aspects of life.

Much thought should go into the décor of the bedroom, where peace and harmony is so important. Here are a few tips:

* Ideally, the bedroom should be as far away as possible from the front door, mirroring the practice of our prehistoric ancestors who did not sleep in the mouth of their cave.

* On entering your bedroom, note where the windows are located. Chi tends to travel between the door and any windows, so avoid positioning your bed in line with this ‘draught’ of chi.

* Position your bed so that you can see the door from where you sleep. This gives you a deep sense of inner security.

* If it is feasible, position your bed as far away from the door as possible.

* Avoid sleeping with your head close to a window as your chi will dissipate through the window and make you feel more tired on awakening.

* Work stations have no place in a bedroom. Avoid having things like desks and computers anywhere near the bed.

* If there's a bathroom in the bedroom, the door should be kept closed at night. This, again, adds to the feeling of safety and protection. Check your bathroom at night. Make sure all the taps are firmly turned off so there's no troublesome drip, drip to keep you awake, then close the door.

* To help you protect your own chi while you are asleep, to internalize it and recharge it, make sure you have a strong, stable headboard. Chi energy enters and exits the body through the feet, hands and the top of the skull, Having a solid ‘mountain’ behind you while you sleep is far more beneficial than a cold, blank wall or worse, the cutting chi of an ornate brass bedstead.

* If you sleep with another person, note the position of your bed relative to the wall that it is up against. Is it equidistant--in the middle of the wall? This is vital in a relationship as it gives both individuals who share the bed equality in the relationship. A shared bed crammed into the corner of a room, is giving more freedom of chi to the individual on the open side whereas the partner will literally and symbolically feel up against a wall.

* Make sure all bedside tables have rounded edges and not square to prevent cutting chi being focused towards the occupants. If two sleep in the bed, ensure matching beside tables on either side for added stability and protection in the relationship.

* Do you really need to have a telephone in the room? If you consider it a necessity, let acquaintances know you don't appreciate late night calls. Of course, this doesn't eliminate wrong numbers and crank calls.

* Ceiling beams above the bed are a Feng Shui nightmare. They can be a source of cutting chi and the beams carry a tremendous load, and this pressure is focused into the beams generating chi which continues downwards, placing direct pressure on you while you sleep.
^Some tips: Paint the beams; drape fabric over the beams; hang bamboo flutes 2-3 inches below the beam to soften the load (the flutes are hung at a 45 degree angle to the beam with the mouthpiece downwards).

* If you sleep with another, make sure your bed is symbolic of this relationship. Beds that are rickety or likely to fall part speak volumes about the state of the relationship.

* Given that the bedroom is a more yin environment, the lighting that you choose needs to reflect this. Soft lighting is ideal. Avoid having ceiling lamps right directly over your bed.

* Pastel colors encourage sleep - pale blue or green. Ivory, light pink or yellow. Bright colors, especially the fluorescents, are bursting with energy. These colors shout at you to get up and get going. Walls and carpets should relax you, not startle the eyeballs till the lids won't close. If your bedroom is a shouter, maybe it's time to repaint. Turn that rebel yell into a sweet lullaby.

* Avoid sleeping with your image visible in a mirror. the worst scenario of all is a mirror at the foot of your bed.

* Place something beautiful that inspires you where you first look in the morning.

* Pay attention to what is under your bed. Keep the space clear and get rid of any unwanted items there.

* Off With the Entertainent. Television sets don't belong in the bedroom. Neither do other forms of entertainment - DVD players. Hand held games. Keep the entertainment equipment in the family room, the living room, the rumpus room. Even the kitchen, if it pleases you. But never in the bedroom. If you really have to have the TV in the bedroom, when it's time to sleep, cover the screen. Do the same with the computer monitor. Covering the mirrors is also a good idea.

* Lights can be disturbing, whether it's the streetlight outside your window, headlights of passing traffic - or even the full moon shining on the bed. In feng shui, however, another reason for covering the windows is to give the sleeper more of a feeling of safety. Yet another reason for covering windows, as well as all reflective surfaces - mirrors, TV screens, computers - is to prevent someone from being startled by a stray reflection of movement - their own - in the glass.

* Not only where you place the bed but everything about it is important when you use feng shui. What's above it, threatening to fall on you and crush you? A heavy light fixture? A ceiling fan? What's below it, sending up old memories or worries? Move the heavy weight from above your head. Clean out the space underneath the bed. Then relax into a good night's sleep.

* Clutter doesn't encourage you to sleep. Clean up the clothing on the floor. Pick up those books and toys. Make your bedroom safe and restful. Don't let clutter collect and invade your sleep.

It's all about keeping surroundings harmonious, Feng shui creates good chi energy and chi energy is life force.
Think peace. Think harmony, Think sleep.

What is HDMI?

From Wikipedia, the free encyclopedia
The High-Definition Multimedia Interface (HDMI) is an all-digital audio/video interface capable of transmitting uncompressed streams. HDMI is compatible with High-bandwidth Digital Content Protection (HDCP) Digital Rights Management technology. HDMI provides an interface between any compatible digital audio/video source, such as a set-top box, a DVD player, a PC, a video game console, or an AV receiver and a compatible digital audio and/or video monitor, such as a digital television (DTV). In 2006, HDMI began to appear as a feature on prosumer HDTV camcorders and even high-end digital still cameras. It is a modern replacement for older analog standards such as RF - coaxial cable, composite video, S-Video, SCART, component video and VGA, and the consumer electronics replacement for older digital standards such as DVI (DVI-D & DVI-I). In the computer world, HDMI is already found on many peripherals and a few newer video cards, with adoption rapidly increasing.

HDMI supports any TV or PC video format, including standard, enhanced, or high-definition video, plus multi-channel digital audio on a single cable. It is independent of the various DTV standards such as ATSC, and DVB (-T,-S,-C), as these are encapsulations of the MPEG movie data streams, which are passed off to a decoder, and output as uncompressed video data on HDMI. HDMI encodes the video data into TMDS for transmission digitally over HDMI.

Devices are manufactured to adhere to various versions of the specification, where each version is given a number, such as 1.0 or 1.3. Each concurrent version of the specification uses the same cables, but increases the throughput and/or capabilities of what can be transmitted over the cable. For example, previously, the maximum pixel clock rate of the interface was 165 MHz, sufficient for supporting 1080p at 60 Hz or WUXGA (1920x1200), but HDMI 1.3 increased that to 340 MHz, providing support for WQXGA (2560x1600) and beyond across a single digital link. See the Versions section for details.

HDMI also includes support for 8-channel uncompressed digital audio at 192 kHz sample rate with 24 bits/sample as well as any compressed stream such as Dolby Digital, or DTS. HDMI supports up to 8 channels of one-bit audio, such as that used on Super Audio CDs at rates up to 4x that used by SuperAudio CD. With version 1.3, HDMI now also supports lossless compressed streams such as Dolby TrueHD and DTS-HD Master Audio.

HDMI is backward-compatible with the single-link Digital Visual Interface carrying digital video (DVI-D or DVI-I, but not DVI-A) used on modern computer monitors and graphics cards. This means that a DVI-D source can drive an HDMI monitor, or vice versa, by means of a suitable adapter or cable, but the audio and remote control features of HDMI will not be available. Additionally, without support for High-bandwidth Digital Content Protection (HDCP) on the display, the signal source may prevent the end user from viewing or recording certain restricted content.

In the USA, on digital TVs with built-in digital (ATSC) tuners, HDCP-support is a standard feature on all but the cheapest digital TVs (which lack HDMI altogether.) Among the PC-display industry, where computer displays rarely contain built-in tuners, HDCP support is absent from many models. For example, the first LCD-monitors with HDMI connectors did not support HDCP, and few compact-LCD monitors (17" or smaller) support HDCP.

The HDMI Founders include consumer electronics manufacturers Hitachi, Matsushita Electric Industrial (Panasonic/National/Quasar), Philips, Sony, Thomson (RCA), Toshiba, and Silicon Image. Digital Content Protection, LLC (a subsidiary of Intel) is providing HDCP for HDMI. In addition, HDMI has the support of major motion picture producers Fox, Universal, Warner Bros., and Disney, and system operators DirecTV and EchoStar (Dish Network) as well as CableLabs and Samsung.


Specifications
HDMI defines the protocol and electrical specifications for the signaling, as well as the pin-out, electrical and mechanical requirements of the cable and connectors.

Connectors
The HDMI Specification has expanded to include three connectors, each intended for different markets. The standard Type A HDMI connector has 19 pins, with bandwidth to support all SDTV, EDTV and HDTV modes and more. The plug outside dimensions are 13.9 mm wide by 4.45 mm high. Type A is electrically compatible with single-link DVI-D. A higher resolution version called Type B is defined in HDMI 1.0. Type B has 29 pins (21.2 mm wide), allowing it to carry an expanded video channel for use with very high-resolution future displays, such as WQSXGA (3200x2048). Type B is electrically compatible with dual-link DVI-D, but is not in general use.

The Type C mini-connector is intended for portable devices. It is smaller than Type A (10.42 mm by 2.42 mm) but has the same 19-pin configuration.

Cable
Each channel in HDMI can be purposed to carry audio, video, multimedia, or device-controlling signals, or a combination of these signals. Adaptor cables - from Type A to Type C - are available.

TMDS channel
The Transition Minimized Differential Signaling (TMDS) channel:
Carries video, audio, and auxiliary data via one of three modes called the Video Data Period, the Data Island Period, and the Control Period. During the Video Data Period, the pixels of an active video line are transmitted. During the Data Island period (which occurs during the horizontal and vertical blanking intervals), audio and auxiliary data are transmitted within a series of packets. The Control Period occurs between Video and Data Island periods.

Signaling method: Formerly according to DVI 1.0 spec. Single-link (Type A HDMI) or dual-link (Type B HDMI). Video pixel rate: 25 MHz to 340 MHz (Type A, as of 1.3) or to 680 MHz (Type B). Video formats with rates below 25 MHz (e.g. 13.5 MHz for 480i/NTSC) transmitted using a pixel-repetition scheme. From 24 to 48 bits per pixel can be transferred, regardless of rate. Supports 1080p at rates up to 120 Hz and WQSXGA [4].
Pixel encodings: RGB 4:4:4, YCbCr 4:4:4 (8-16 bits per component); YCbCr 4:2:2 (12 bits per component)
Audio sample rates: 32 kHz, 44.1 kHz, 48 kHz, 88.2 kHz, 96 kHz, 176.4 kHz, 192 kHz.
Audio channels: up to 8.
Audio streams: any IEC61937-compliant stream, including high bitrate (lossless) streams (Dolby TrueHD, DTS-HD Master Audio).


Consumer Electronics Control channel
The Consumer Electronics Control (CEC) channel is optional to implement, but wiring is mandatory. The channel:
Uses the industry standard AV Link protocol
Used for remote control functions.
One-wire bidirectional serial bus.
Defined in HDMI Specification 1.0, updated in HDMI 1.2a, and again in 1.3a (Added timer and audio commands).

This feature is used in two ways:
- To allow the user to command and control multiple CEC-enabled boxes with one remote control, and
- To allow individual CEC-enabled boxes to command and control each other, without user intervention.
An example of the latter is to allow the DVD player, when the drawer closes with a disk, to command the TV and the intervening A/V Receiver (all with CEC) to power-up, select the appropriate HDMI ports, and auto-negotiate the proper video mode and audio mode. No remote control command is needed. Similarly, this *type* of equipment can be programmed to return to sleep mode when the movie ends, perhaps by checking the real-time clock. For example, if it is later than 11:00pm, and the user does not specifically command the systems with the remote control, then the systems all turn off at the command from the DVD player.


Content protection
According to High-bandwidth Digital Content Protection (HDCP) Specification 1.2.
Beginning with HDMI CTS 1.3a, any system which implements HDCP must do so in a fully-compliant manner. HDCP compliance is itself part of the requirements for HDMI compliance. The Hdmi repeater bit controls the authentication and distribution from a single source to multiple displays.


Cable length
The HDMI specification does not define a maximum cable length. As with all cables, signal attenuation becomes too high at a certain length. Instead, HDMI specifies a minimum performance standard. Any cable meeting that specification is compliant. Different construction quality and materials will enable cables of different lengths. In addition, higher performance requirements must be met to support video formats with higher resolutions and/or frame rates than the standard HDTV formats.

The signal attenuation and intersymbol interference caused by the cables can be compensated by using Adaptive Equalization.

HDMI 1.3 defined two categories of cables: Category 1 (standard or HDTV) and Category 2 (high-speed or greater than HDTV) to reduce the confusion about which cables support which video formats. Using 28 AWG, a cable of about 5 metres (~16 ft) can be manufactured easily and inexpensively to Category 1 specifications. Higher-quality construction (24 AWG, tighter construction tolerances, etc.) can reach lengths of 12 to 15 metres (~39 to 49 ft). In addition, active cables (fiber optic or dual Cat-5 cables instead of standard copper) can be used to extend HDMI to 100 metres or more. Some companies also offer amplifiers, equalizers and repeaters that can string several standard (non-active) HDMI cables together.


HDMI and high-definition optical media players
Both introduced in 2006, Blu-ray Disc and HD DVD offer new high-fidelity audio features that require HDMI for best results. Dolby Digital Plus (DD+), Dolby TrueHD and DTS-HD Master Audio use bitrates exceeding TOSLINK's capacity. HDMI 1.3 can transport DD+, TrueHD, and DTS-HD bitstreams in compressed form. This capability would allow a preprocessor or audio/video receiver with the necessary decoder to decode the data itself, but has limited usefulness for HD-DVD and BluRay.
HD-DVD and BluRay permit "interactive audio", where the disc-content tells the player to mix multiple audio sources together, before final output. Consequently, most players will handle audio-decoding internally, and simply output LPCM audio all the time. Multichannel LPCM can be transported over an HDMI 1.1 (or higher) connection. As long as the audio/video receiver (or preprocessor) support multi-channel LPCM audio over HDMI, and support HDCP, the audio reproduction is equal in resolution to HDMI 1.3.

Many low-end audio receivers do not support audio over HDMI, and are sometimes labeled "HDMI passthrough" devices. In the future, it is likely that most devices claiming HDMI 1.1 as a feature will support at least 5.1 LPCM over HDMI.