Sleeping Brain Waves March 17, 2009Posted by healthyself in Biological Activity, Blogroll, Sleep.
“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, … consistent oscillations at about 10 cycles per second. An alert person generates beta waves, …. about twice as fast. During sleep, two slower patterns called theta waves and delta waves take over. Theta waves have oscillations in the 3.5 to 7 cycle per second range… delta waves are … below 3.5 cycles per second. As a person falls asleep and sleep deepens, the brainwave patterns slow down. The slower the brain wave patterns, the deeper the sleep – a person deep in delta wave sleep is hardest to wake …. At several points during the night, Rapid Eye Movement (REM) sleep occurs, and brainwaves during this period speed up to awake levels (alpha or beta).”
“…[A} pervasive misconception about sleep is that [it] is just a matter of ..bodies “turning off” for several hours, followed by … bodies “turning back on” when … awake. …most of us think of sleep as a passive and relatively constant and unchanging process…. sleep is a very active state. … bodies move frequently… roll about during the night… brain activity is even more varied than it is during the normal waking state. …”
Sleep Stages: Measures
” …. [There are} three fundamental measures... basis for defining stages of sleep....gross brain wave activity ... as measured by an electroencephalogram (EEG)...[which] provides the summary of electrical activity from one area of the brain. … muscle tone is measured with a electromyogram (EMG) machine…. eye movement is recorded via an electro-oculogram (EOG)….
“…The EEG reading is the most important measure in differentiating between the stages, while the EMG and EOG are most important in differentiating rapid eye movement (REM) sleep from the other stages.
Sleep Stages: Waking through Stage 2
“….When awake, most people exhibit brain wave, (EEG) patterns that can be classified into two types of waves, beta and alpha. Beta waves are those associated with day to day wakefulness. These waves are the highest in frequency and lowest in amplitude, and… more desynchronous than other waves…. the waves are not very consistent in their pattern. This desynchrony makes sense given that day to day mental activity consists of many cognitive, sensory, and motor activities and experiences, and, thus, when awake, we are mentally desynchronous …”
“During periods of relaxation, while… awake, …brain waves become slower, increase in amplitude and become more synchronous. These types of waves are called alpha waves. … such brain waves are often associated with states of relaxation and peacefulness during meditation and biofeedback….. recent evidence indicates that activities that promote alpha wave activity, appear to have positive health benefits.”
“The first stage of sleep is characterized by theta waves, which are even slower in frequency and greater in amplitude than alpha waves. The difference between relaxation and stage 1 sleep is gradual and subtle. As the sleeper moves to stage 2 sleep theta wave activity continues, interspersed with two unusual wave phenomena. These phenomena, which occur periodically every minute or so, and are defining characteristics of stage 2 sleep, are termed sleep spindles and K complexes … The former is a sudden increase in wave frequency, and the latter is a sudden increase in wave amplitude. Stages 1 and 2 are relatively “light” stages of sleep. In fact, if someone is… [wakened] during one of these stages, he or she will often report not being asleep…”
Sleep Stages: Delta Sleep, REM, and the Sleep Cycle
“During a normal nights sleep a sleeper passes from the theta waves of stage 1 and 2, to the delta waves of stage 3 and 4. Delta waves are the slowest and highest amplitude brain waves. There is no real division between stages 3 and 4 except that, typically, stage 3 is considered delta sleep in which less than 50 percent of the waves are delta waves, and in stage 4 more than 50 percent of the waves are delta waves. Delta sleep is our deepest sleep, the point when our brain waves are least like waking. Consequently, it is most difficult stage in which to wake sleepers,… when they are awakened they are usually sleepy and disoriented…. delta sleep is when sleep walking and sleep talking is most likely to occur.”
“… another, unique, stage of sleep exists, REM. This stage gets its name from the darting eye movements that accompany it (rapid eye movement), as indicated by the EOG…. characterized by a sudden and dramatic loss of muscle tone, which is measured by the EMG. In fact, the skeletal muscles of a person during REM sleep are effectively paralyzed. This stage is …associated with a unique brain wave pattern…during REM sleep a sleepers brain waves demonstrate characteristics…similar to waking sleep, a combination of alpha, beta, and desynchronous waves…. this is the stage of sleep most associated with dreaming. When a sleeper in a research lab begins to exhibit the physiological indices of R.E.M sleep, and they are awakened, the great majority of the time they will report that they were having a vivid, story-like, dream. During other stages, on the other hand, they normally do not report dreaming….”
The vivid recall that could be elicited in the middle of the night when a subject was awakened while his eyes were moving rapidly was nothing short of miraculous. It [seemed to open] … an exciting new world to the subjects whose only previous dream memories had been the vague morning-after recall. Now, instead of perhaps some fleeting glimpse into the dream world each night, the subjects could be tuned into the middle of as many as ten or twelve dreams every night.
(Dement, 1978, p. 37; quoted in Pinel, 1993)
“In a normal night’s sleep, a sleeper begins in stage 1, moves down through the stages, to stage 4, then back up through the stages, with the exception that stage 1 is replaced by REM, then the sleeper goes back down through the stages again. One cycle, from stage 1 to REM takes approximately ninety minutes. This cycle is repeated throughout the night, with the length of REM periods increasing, and the length of delta sleep decreasing, until during the last few cycles there is no delta sleep at all.”