You’ve got one amazing brain. It allows for states of being awake and asleep, with distinct phases during those two states. In fact, there are three states of consciousness: awake, REM, and Non REM.
'Mixed phases' of sleep and wakefulnessThere is reason to believe that these three phases are not totally exclusive from the others. It’s really a matter of which phase, in any given period of time, has predominance. The brain experiences activity with ebbs and flows amid phases. For example, you can be fully awake, but have dazed periods with what is known as micro-sleep. There are also times when you have periods of** micro-arousal** during sleep. The reason we are able to function well with those “mixed phases” is because only some parts of the brain deviate from the main frame of activity.
Scientific findings suggest that certain portions of the brain act independently, meaning all activities of the brain are not necessarily in unison in a given moment.
Even during waking hours, parts of the brain are more active than others. This allows the brain to adapt and then pay specific attention to a certain task. Researchers at Stanford University have termed this behavior “selective attention,” in which small parts of the brain are more awake.
Cycling on and off
Selective parts of the brain actually go through periods of cycling on and off, fluctuating between high and low activity. This can occur even during tasks that require focused attention.
How? The brain uses a lot of energy and cycling off for periods may allow certain groups of brain cells to save energy. It may also help to prevent the accumulation of cellular byproducts, and allow the brain to function and manage tasks for more extended periods of time. Cycling allows the brain to pace itself so that it lasts longer while managing a cognitive task. Picture a marathon runner pacing himself in order to last the full distance of the run.
There are also other ways that the brain can sustain the energy required to perform all the tasks demanded of it throughout the day. The brain does this by spending some of the time in a “less than awake” phase.
The best known state between sleep and wake is the alpha state. Alpha waves measure between seven and 14 cycles per second. Brainwave frequency that is considered sleep measures fewer than seven cycles per second. Alpha state typically occurs during relaxation, when a person rests with eyes closed. This state gained particular attention when biofeedback became more popular. This technique uses sounds to train and then prompt the individual to reach the alpha state and to recognize when it’s achieved. The brain in alpha state can help to enhance relaxation and memory, manage pain, lower blood pressure, and even decrease the threshold for seizures.
There are also other uses for training people to reach alpha state. Psychologists can use this technique to help calm hyperactive children and help individuals who struggle with stuttering problems
Being awake is not an all-or-nothing phenomenon
As mentioned earlier, there are also periods during wakefulness when there is sleep. That’s when someone will feel his or her attention wandering. It’s also experienced as slowed reaction time or when someone has less emotional control. So being awake is not an all-or-nothing phenomenon. When you’re awake the entire brain might not be awake. This is especially evident during monotonous activities like driving long distances, when a period of micro-sleep can be quite dangerous.
The psychomotor vigilance test is used to measure a person’s alertness and can help to identify if a person is experiencing micro-sleeps during what should be wakeful periods. Sleep experts also use other tests to measure “brain fatigue,” and these assessments are especially important in jobs where the safety of others is involved. Commercial pilots and train operators have been under scrutiny lately because of suspected micro-sleep problems, which have resulted in deadly accidents.
Experts are also currently working on developing more testing methods so they can accurately measure "selective attention" (mentioned earlier). It would be helpful to further explore if there are individual differences in one’s ability to sustain selective attention and whether it affects one's ability to concentrate on certain tasks. It would also help to be able to measure how long an individual can sustain selective attention.
The next time you think you can stay awake for a long period of time, remember that your brain may “take over” and induce micro-sleep to compensate, whether you are aware of it or not. If you know you are already sleep-deprived, avoid taking a long drive or trying to complete a brain wearying-task like solving your child’s complicated math homework. Your brain and its micro-sleep mechanism will likely thwart your efforts!
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Eli Hendel, M.D. is a board-certified Internist and pulmonary specialist with board certification in Sleep Medicine. He is an Assistant Clinical Professor of Medicine at Keck-University of Southern California School of Medicine, Qualified Medical Examiner for the State of California Department of Industrial Relations, and Director of Intensive Care Services at Glendale Memorial Hospital. His areas of expertise in private practice include asthma, COPD, sleep disorders, obstructive sleep apnea, and occupational lung diseases.