Sleep, Sensation & Perception

Electroencephalogram (EEG)

-Measures electrical activity in brain (brain waves, frequency/amplitude)

-Through electrodes that measure electrical impulses generated by large groups of cortical neurons

Non-REM sleep

-3 stages (N1, N2, and N3)

-quiet sleep, low frequency, high amplitude; synchronized activity

REM sleep

-active sleep, high frequency, low amplitude

-paradoxical sleep – active brain and physiological arousal, but major muscles nearly paralyzed

-very difficult to arouse

N1

-alpha waves (awake/relaxed, drowsy) → theta

-falling asleep

-if someone awakes during N1, may deny they were sleeping

N2

-theta waves continue

-are interrupted by sleep spindles (sudden bursts of fast waves) + K-complexes (large, slow waves)

-relaxed muscles, slowed breathing, reduced HR

-body temperature drops

N3

(Deep, Delta)

-aka slow-wave sleep, Deepest level of sleep

-theta → Delta waves (slower/low frequency compared to theta; high amplitude)

-difficult to awaken during N3

REM/Stage R

-BETA waves (characteristic of awake and alert state) + THETA waves

-(paradoxical) temporary muscle paralysis + active sleep

-very difficult to arouse

NREM/REM cycling in normal adults

-REM stages get longer throughout the night

-N3 gets shorter

Sleep in newborn infants

-more time in REM (active sleep)

-start in REM/active → non-REM/quiet

-sleep longer (14-16 hrs)

Sleep in older adults

-more trouble falling asleep, wake up more often

-evenly distributed REM sleep over the night (instead of increasingly longer REM)

-shorter deep sleep (shorter N3)

-Advanced sleep phase (aka circadian phase advance) – go to sleep earlier, wake up earlier

Cones

-Color

-Visual acuity (sharpness, precise detail)

-Best in bright light

Rods

-Responsible for dim light vision (more light-sensitive); don’t perceive color

-Peripheral vision