Brain waves are a measure of electrical changes that take place in our brain. They are measured with a monitoring machine called an EEG, or electroencephalograph. An EEG is a completely non-invasive test: it is not painful or uncomfortable, and involves sensors known as electrodes being placed along key points along the scalp. The electrodes relay the information that they gather about brain activity to a pen moving along a moving sheet of paper. The end result is very similar to what we have seen in crime dramas when a suspect is given a polygraph – or lie detector – test: lines that move up and down in varying heights and rhythms that sleep scientists are able to read and interpret. These lines reflect our brain’s activity level, and are called brain waves.
There are several distinctive brain wave patterns that sleep scientists are able to identify. They are:
- Beta Waves
- Alpha Waves
- Theta Waves
- Sleep Spindles and K-Complexes
- Delta Waves
- REM Sleep
Beta Waves do not have a large jump of highs and lows. They reflect low-voltage electrical activity and are spaced very closely together, indicating that the electrical activity is rapid. Beta Waves are present when we are fully awake and alert.
When we are transitioning from wakefulness to sleep we enter a period that is referred to as calm wakefulness. This is the period when we turn out the lights, close our eyes and wait for sleep to come, and the brain waves that are exhibited during this stage are called Alpha Waves. Alpha Waves show stronger high-low jumps as they emit a higher energy level of electrical activity, but they are slow.
Alpha Waves lead directly into Theta Waves, and it is the abrupt change from one to the other that marks the moment when we actually fall asleep and lose all sense of the world around us. Theta Waves show the same high-low jumps that Alpha Waves do, but they slow down even further. They appear during Stage I sleep, the period in which our mind is closed off but we can still be roused easily. This stage only lasts about five minutes before transitioning to Stage 2 sleep, which is characterized by Sleep Spindles and K-Complexes.
Sleep Spindles and K-Complexes are brain wave patterns that appear intermittently, in short bursts. They last only a few seconds and represent a burst of energy that appears in the midst of a period of Theta Waves. It is thought that they represent a shift in how the brain is processing information.
Stage 3 sleep is deep sleep, and introduces the brain wave called the Delta Wave. They have tremendous highs and lows that are spaced far apart – the best word to describe them is undulating. During Stage 3 sleep Delta Waves can still be interrupted by Sleep Spindles and K-Complexes, but these quickly disappear and the brain enters Stage 4 sleep, which is all uninterrupted Delta Waves. For this reason Stage 4 sleep is sometimes referred to as slow-wave sleep.
After a long period of Stage 4 sleep, the body reverts back to Stage 3 sleep and Theta Waves with Sleep Spindles and K-Complexes reappear. This is an indication that we are about to enter REM sleep, the time when our eyes make rapid movements and during which we dream. REM sleep is characterized by the absence of Delta Waves and the appearance of Theta Waves interrupted by occasional Alpha and Beta Waves. Though Alpha and Beta on their own are generally reflective of being in a period of wakefulness, when they occur during REM sleep they reflect the level of activity that is taking place within the sleeper’s dream. When a REM sleep period is complete the brain waves return to the Delta Waves of Stage 3 and Stage 4 sleep.
Brain waves and sleep patterns in normal sleep are both predictable and identifiable. The pattern described here recurs throughout the course of the night, with children’s periods of deep sleep and REM sleep occurring with different frequencies and lengths of time as compared to adults, and these time periods adjust again as we age. Though it is fascinating to watch the progression of brain waves that indicate the different sleep stages that we pass through each night, this window into sleep is most useful when it is employed to detect shifts in the normal pattern. These shifts are straightforward indications that all is not well within a person’s sleep pattern, and by analyzing them scientists and sleep physicians are able to help solve problems of insomnia, restlessness and sleep deprivation. Scientists are also able to determine whether sound sleepers exhibit different patterns of brain waves when exposed to loud noises or other disruptions.
The sleep dynamic that is described here is the norm, and it has evolved in order to provide the human body with the rest that it needs in order to go about each day in the most effective and functional way. When the pattern is interrupted, whether by being shortened due to activity or insomnia, by drugs or alcohol, by illness or by something going wrong within the brain, fatigue and stress can ensue.
Sleep scientists are hopeful that the use of brain wave monitoring by EEG machines will eventually go beyond its current usefulness in diagnosing sleep disorders and will become integral in developing new sleep therapies. Among the possibilities being discussed are a technology that would allow an EEG to be utilized on a regular basis for those suffering from sleep disorders and, upon detection of disruption in a healthy brain wave pattern, administering a sleep medication that would return the patient to the appropriate sleep stage. This type of technology would allow for a much-reduced amount of medication to be used, and yet used more effectively.