what do you fear?
Nightmares
Nightmares are essentially bad dreams. We all get them at some point or another, but are generally more common in adolescents. The cause of nightmares is not known, however there are many risk factors including irregular sleeping patterns, stress and anxiety during the day, and not getting enough sleep. Dreams are our brains' way of working out problems, so nightmares are more common when there is a frightening situation during the day. Evolution gets rid of any unnecessary adaptations that we may possess. Researchers believe that nightmares are still around in order to help protect ourselves. Their job is to warn us of any dangers that we may face during the day and help find solutions to them. Nightmares are more common in infants with mental retardation, depression, or certain diseases of the brain. Constant nightmares may be an indicator of Post-Traumatic Stress Disorder. Fevers and certain medications have also been known to cause nightmares. Nightmare Disorder, or dream anxiety disorder, is a sleep disorder in which individuals are plagued by constant nightmares. Many mental conditions and psychiatric disorders lead to nightmares.
Night Terrors: Not to be confused with nightmares, night terrors are a completely different experience. A night terror consists of suddenly waking up from sleep and screaming. It is often followed by confusion, rapid heart rate, and sweating. This can last anywhere from 5 to 20 minutes.The subject's eyes are often open, but they are still asleep. Even after waking up it is hard to remember the episode, other than the intense feeling of fear. Nightmares occur during REM sleep, while night terrors occur during stage 4 NREM sleep.
When you fall into REM sleep, your brain goes into overdrive and allows dreams to be created. The part of the brain that signals REM sleep is the pons, and is located in the hindbrain. Adults spend 20% of their sleep in REM sleep, as opposed to infants that experience 50%. This explains why infants are able to retain information and learn better than adults. Studies have shown that REM sleep is a time period of learning and storing of memories in the brain, and dreams help decipher events that have occurred. Roughly 90% of REM sleep is spent dreaming, so we experience a total of 2 hours of dreams each night, broken up by the sleep cycle. Dreams can occur during NREM sleep, but are often forgotten. The dreams we remember the next day occur during REM sleep. Even when sleeping the brain is never at rest. During sleep, parts of the brain that remain relatively inactive during the day are fired up, and cause a spike in imagination. The Limbic system becomes much more active than during the day, leading to dreams filled with emotion. The center of fear, the amygdala, is located in the limbic system making it likely to have dreams with the individual's greatest fears within them. Once monsters or other fears are dreamed up, our brain accepts them because the prefrontal cortex ceases almost all activity. Being the main component of rational thought, our ability to reason is shut off during sleep. The primary visual cortex is inactive during REM sleep, but not the secondary visual cortex. No data is being taken in directly from the eyes, but the visuals we see during dreams are interpreted by the secondary visual cortex.
Rapid Eye Movement Vs. Non-Rapid Eye Movement
Rapid Eye Movement sleep is the section of sleep when there are rapid eye movements. Dreams can only occur in REM sleep. Humans generally experience 3 - 5 periods of REM sleep each night, occuring every 1 - 2 hours. Episodes of REM sleep vary in length. They can last for five minutes, or for over an hour. 20% of our sleep is spent in REM sleep. If an individual gets 8 hours of sleep each night, they will spend roughly 90 minutes within REM sleep. Along with being associated with our dreams, REM sleep is accomanpied by irregular heart rate, breathing, and involuntary muscle movements. In order to study brain activity and map brain waves during sleep, scientists utilize the electroencephalographic machine, or EEG. While in REM sleep, the EEG is able to record rapid, low voltage waves emitted by our brains.
NREM, or non-REM sleep is referred to as dreamless sleep. It differs from REM sleep in that our respiration and heart rates remain regular, our blood pressure is low, and we remain relatively still. When in NREM sleep, our brain activity is also distinctly different from REM sleep. As opposed to the fast waves in REM sleep, our brain waves are slower and higher voltage. NREM sleep is separated into 4 stages, all leading up to the REM sleep stage.
The full sleep cycle occurs from 4 to 6 times a night, starting off with stage 1 of NREM sleep. After the full 4 stages of NREM sleep, the sleeper slips into REM sleep. After the first REM phase is complete, the cycle starts back at stage 1. The longer we stay sleeping, the less deep sleep we receive. After the first two cycles, when deep sleep dominates the cycle, the amount of deep sleep decreases and the amount of REM sleep increases. It is impossible to deprive someone of REM sleep. If REM sleep is cut short or no sleep is allowed, the individual will shift straight into REM sleep as soon as sleep initially occurs.
NREM, or non-REM sleep is referred to as dreamless sleep. It differs from REM sleep in that our respiration and heart rates remain regular, our blood pressure is low, and we remain relatively still. When in NREM sleep, our brain activity is also distinctly different from REM sleep. As opposed to the fast waves in REM sleep, our brain waves are slower and higher voltage. NREM sleep is separated into 4 stages, all leading up to the REM sleep stage.
The full sleep cycle occurs from 4 to 6 times a night, starting off with stage 1 of NREM sleep. After the full 4 stages of NREM sleep, the sleeper slips into REM sleep. After the first REM phase is complete, the cycle starts back at stage 1. The longer we stay sleeping, the less deep sleep we receive. After the first two cycles, when deep sleep dominates the cycle, the amount of deep sleep decreases and the amount of REM sleep increases. It is impossible to deprive someone of REM sleep. If REM sleep is cut short or no sleep is allowed, the individual will shift straight into REM sleep as soon as sleep initially occurs.
Stages of NREM Sleep
The first stage of NREM sleep is a sort of twilight period. Brain waves become smaller, slower, and less voltage on an EEG. Heart and breathing rates become slower and more even, and the brain receives less blood flow. The first stage generally lasts 10 minutes, and sleepers can be easily woken up. Stage two of NREM sleep is a transition stage where the sleeper begins falling into a deep sleep. It lasts roughly 20 minutes and leads into a deep sleep. Our brain waves become slightly larger and occasionally receive quick bursts of activity. Bodily functions including metabolism, secretion, and cardiac activity decrease as the sleeper becomes more detached from the outside world. The third stage is the beginning of deep sleep, starting between 30 and 45 minutes after initially falling asleep. The biggest change in is in our brain's activity. Our brain waves turn to delta waves, meaning they are slow, but up to 5 times the size of the waves in stage 2. It becomes much harder to wake someone up in this stage, and requires an active attempt to do so. The fourth stage of NREM sleep is similar to that of the third in that the delta waves continue. Delta waves are seen more frequently in the sleep of infants, and the amount of time spent in these stages decreases with age. By age 75, it is likely that the sleeper will not experience stages 3 and 4 of REM sleep. One role of delta waves is to release the hormone GHRH from the hypothalamus, or Growth Hormone Releasing Hormone, which causes the pituitary to release Human Growth Hormone. While in stage 4 NREM sleep and the brain is shooting out delta waves, the sleeper is totally detached from the conscious world. Sleep walking, sleep talking, and bed wetting occur during this stage. If one is woken up during this stage of sleep, they will often experience sleep inertia. Sleep inertia is the inability of an individual to function properly after waking up. It generally occurs if they did not get enough sleep or they were just in a very deep sleep.
Upon entering REM sleep, the brain's activity increases drastically. The EEG of waves in REM sleep resemble being awake more closely than being asleep. While NREM sleep works to slow the body's functions down, REM sleep perks up the activity greatly. Blood pressure, pulse rates, and breathing rates become irregular and increase in activity. The sleeper's large muscles become paralyzed, due to a small region in the brain stem. This nightly paralysis is necessary for our own safety because it disables us from acting out our dreams. People can receive constant injury or injure others around them if they have REM Sleep Disorder, or the absence of bodily paralysis during REM Sleep. Sweating and shivering no longer occurs during REM sleep as the body's temperature changes to that of its environment. The body stops regulating temperature.
Sources:
http://www.nytimes.com/2007/10/23/science/23angi.html?_r=1&pagewanted=2
http://biology.about.com/od/anatomy/p/pons.htm
http://longevity.about.com/od/sleep/a/dreams_REM.htm
http://www.holisticonline.com/remedies/sleep/sleep_stages-1-4NREM.htm
http://www.nightterrors.org/mot.htm
http://www.lifeslittlemysteries.com/why-do-we-have-nightmares-0978/
(picture) http://dyingscene.com/wp-content/uploads/NIGHTMARE.jpg
Upon entering REM sleep, the brain's activity increases drastically. The EEG of waves in REM sleep resemble being awake more closely than being asleep. While NREM sleep works to slow the body's functions down, REM sleep perks up the activity greatly. Blood pressure, pulse rates, and breathing rates become irregular and increase in activity. The sleeper's large muscles become paralyzed, due to a small region in the brain stem. This nightly paralysis is necessary for our own safety because it disables us from acting out our dreams. People can receive constant injury or injure others around them if they have REM Sleep Disorder, or the absence of bodily paralysis during REM Sleep. Sweating and shivering no longer occurs during REM sleep as the body's temperature changes to that of its environment. The body stops regulating temperature.
Sources:
http://www.nytimes.com/2007/10/23/science/23angi.html?_r=1&pagewanted=2
http://biology.about.com/od/anatomy/p/pons.htm
http://longevity.about.com/od/sleep/a/dreams_REM.htm
http://www.holisticonline.com/remedies/sleep/sleep_stages-1-4NREM.htm
http://www.nightterrors.org/mot.htm
http://www.lifeslittlemysteries.com/why-do-we-have-nightmares-0978/
(picture) http://dyingscene.com/wp-content/uploads/NIGHTMARE.jpg
