In such instances, REM rebound may actually represent an adaptive response to stress in nondepressed individuals by suppressing the emotional salience of aversive events that occurred in wakefulness (Suchecki, Tiba, & Machado, 2012). Aside from the role that REM sleep may play in processes related to learning and memory, REM sleep may also be involved in emotional processing and regulation. This is known as the REM rebound, and it suggests that REM sleep is also homeostatically regulated. If people are deprived of REM sleep and then allowed to sleep without disturbance, they will spend more time in REM sleep in what would appear to be an effort to recoup the lost time in REM. The brain waves associated with REM sleep, outlined in the red box in (a), look very similar to those seen (b) during wakefulness. Like NREM sleep, REM has been implicated in various aspects of learning and memory (Wagner, Gais, & Born, 2001), although there is disagreement within the scientific community about how important both NREM and REM sleep are for normal learning and memory (Siegel, 2001).įigure 4.12 (a) A period of rapid eye movement is marked by the short red line segment. Therefore, no movement of voluntary muscles occurs during REM sleep in a normal individual REM sleep is often referred to as paradoxical sleep because of this combination of high brain activity and lack of muscle tone. It is also associated with paralysis of muscle systems in the body with the exception of those that make circulation and respiration possible. The brain waves associated with this stage of sleep are very similar to those observed when a person is awake, as shown in Figure 4.12, and this is the period of sleep in which dreaming occurs. REM SleepĪs mentioned earlier, REM sleep is marked by rapid movements of the eyes. It is relatively easy to wake someone from stage 1 sleep in fact, people often report that they have not been asleep if they are awoken during stage 1 sleep.įigure 4.11 (a) Delta waves, which are low frequency and high amplitude, characterize (b) slow-wave stage 3 and stage 4 sleep. Theta waves are even lower frequency (4–7 Hz), higher amplitude brain waves than alpha waves. As an individual continues through stage 1 sleep, there is an increase in theta wave activity. This pattern of brain wave activity resembles that of someone who is very relaxed, yet awake. The early portion of stage 1 sleep produces alpha waves, which are relatively low frequency (8–13Hz), high amplitude patterns of electrical activity (waves) that become synchronized ( Figure 4.9). In terms of brain wave activity, stage 1 sleep is associated with both alpha and theta waves. In addition, stage 1 sleep involves a marked decrease in both overall muscle tension and core body temperature. During this time, there is a slowdown in both the rates of respiration and heartbeat. Stage 1 sleep is a transitional phase that occurs between wakefulness and sleep, the period during which we drift off to sleep. The first stage of NREM sleep is known as stage 1 sleep. (credit "sleeping": modification of work by Ryan Vaarsi) NREM Stages of Sleep In this section, we will discuss each of these stages of sleep and their associated patterns of brain wave activity.įigure 4.8 Brainwave activity changes dramatically across the different stages of sleep. The first four stages of sleep are NREM sleep, while the fifth and final stage of sleep is REM sleep. In contrast, non-REM (NREM) sleep is subdivided into four stages distinguished from each other and from wakefulness by characteristic patterns of brain waves. Brain waves during REM sleep appear very similar to brain waves during wakefulness. Rapid eye movement (REM) sleep is characterized by darting movements of the eyes under closed eyelids. Sleep can be divided into two different general phases: REM sleep and non-REM (NREM) sleep. These changes in brain wave activity can be visualized using EEG and are distinguished from one another by both the frequency and amplitude of brain waves ( Figure 4.8). Instead, sleep is composed of several different stages that can be differentiated from one another by the patterns of brain wave activity that occur during each stage. Understand the role that REM and non-REM sleep play in learning and memory.Describe the differences between the four stages of non-REM sleep.Differentiate between REM and non-REM sleep.Learning Objectives By the end of this section, you will be able to:
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