What Is Arousal?

Arousal is an abrupt change in the pattern of brain wave activity, as measured by an EEG. Arousal typically represents a shift from deep sleep, which is commonly known as REM sleep, to light sleep, known as NREM sleep, or from sleep to wakefulness.

As it sounds, arousal is when a person becomes ‘aroused’ to some extent during the sleep cycle. It is a sudden change in brain wave activity. It does not necessarily mean that the person has woken entirely, but could just mean a shift out of extremely deep sleep to a lighter sleep, from which it is easier to be woken up from.

Arousal is an abrupt change in the pattern of brain wave activity, but what exactly is a brain wave?

A brain wave is the summation of the electrical activity of numerous neurons. Brain waves are typically recorded by an EEG, or electroencephalogram test. These rapid change in voltage of brain activity occur between different sections of the brain. Brain waves can be utilized to assess the level of consciousness or sleep stage of an individual, and thus can be used to measure arousal.

Sleep occurs in two basic states throughout the night. The two stages of sleep are rapid eye movement sleep (REM) and nonrapid eye movement sleep (NREM). REM is a deep stage of sleep with intense brain activity in the forebrain and midbrain. It is characterized by dreaming and the absence of motor function with the exception of the eye muscles and the diaphragm. It occurs cyclically several times during sleep, but it comprises the smallest portion of the sleep cycle.

The other basic state of sleep is nonrapid eye movement sleep, or NREM sleep. Arousal occurs more often during states of NREM sleep, which consists of three separate stages. The three stages are N1, N2, and N3, and each separate state has unique, distinct, and recognizable electrical brain wave patterns. While REM sleep is the deepest state of sleep, NREM sleep takes up the largest portion of the overall sleep cycle.

Arousal typically represents a shift in sleep states. Arousal can be a shift from REM sleep to NREM sleep, or from NREM sleep to a state of being awake.

Arousal can become an issue if it occurs consistently throughout an evening. It can prevent an individual from getting a solid night's sleep, and also from getting a deep sleep.

Exercise is often suggested as a method to help eliminate arousal. Exercising during the day can work to tire out the body, and prepare it for a solid night's sleep. Exercise can help to promote a sound sleep, and thus work to potentially minimize arousal occurrences. If one is exhausted, they are more likely to sleep through the night.

Examples: She had a brief arousal from deep sleep but did not completely awaken as she stayed in a lighter stage of sleep.