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Module 1.5b

your heart rate, which increases your alertness [Moorcroft, 2003].) When you are ready
for bed, a researcher comes in and tapes electrodes to your scalp (to detect your brain Waking beta waves
waves), on your chin (to detect muscle tension), and just outside the corners of your
eyes (to detect eye movements) (Figure 1.5-4). Other devices may record your heart rate, Waking alpha waves
respiration rate, and genital arousal.

Left eye movements
Stage 1
Right eye movements

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EMG (muscle tension)
Stage 2

Hank Morgan/Science Source EEG (brain waves) Stage 3 (delta waves)

Figure 1.5-4 Rebecca Spencer, University of Massachusetts, assisted with this illustration.
Measuring sleep activity REM
Sleep researchers measure brain-wave activity, eye movements, and muscle tension with
electrodes that pick up weak electrical signals from the brain, eyes, and facial muscles
(Dement, 1978). Copyright © Bedford, Freeman & Worth Publishers.
6 sec

When you are in bed with your eyes closed, the researcher in the next room sees on the Figure 1.5-5
EEG the relatively slow alpha waves of your awake but relaxed state (Figure 1.5-5). As time Brain waves and sleep
stages
wears on, you adapt to all this equipment, grow tired and, in an unremembered moment, The beta waves of an alert,
slip into sleep (Figure 1.5-6). This transition is marked by the slowed breathing and the waking state and the regular
irregular brain waves of Stage 1 sleep. (Sleep stages 1, 2, and 3 are now called N1, N2, and alpha waves of an awake, relaxed
N3 — indicating that they occur during NREM sleep.) state differ from the slower, larger
delta waves of deep Stage 3
sleep. Although the rapid REM
sleep waves resemble the near-
waking Stage 1 sleep waves, the
body is more internally aroused
Sleep 1 second during REM sleep than during
NREM sleep (Stages 1, 2, and 3).
Figure 1.5-6
The moment of sleep
Although we are unaware of the moment we fall into sleep, someone
watching our brain waves could tell (Dement, 1999).

In one of his 15,000 research participants, William Dement (1999) observed the moment alpha waves the relatively slow
the brain’s perceptual window to the outside world slammed shut. Dement asked this brain waves of a relaxed, awake
sleep-deprived young man with eyelids taped open to press a button every time a strobe light state.
flashed in his eyes (about every 6 seconds). After a few minutes, the young man missed one. NREM sleep non-rapid eye
movement sleep; encompasses
Asked why, he said, “Because there was no flash.” But there was a flash. He had missed it all sleep stages except for REM
because (as his brain activity revealed) he had fallen asleep for 2 seconds, missing not only the sleep.
flash 6 inches from his nose but also the awareness of the abrupt moment of entry into sleep.

Sleep: Sleep Stages and Theories Module 1.5b 95

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