EEG tracings during sleep

When researchers examined the EEG tracings from a single electrode across an entire night's sleep, they found a similar pattern: Slower waves were associated with greater relaxation. Brain activity gradually slowed as a person drifted off to sleep, then got steadily slower and more regular as the person moved into deeper and deeper sleep.



The "waves" recorded on the tracings got progressively slower (lower in frequency) and larger (higher in amplitude) during the first hour or so after the person fell asleep.