Which stage of sleep is characterized by sleep spindles,which appear against a background of mixed,mostly lower frequency EEG activity

A)  stage 1 
B)  stage 2 
C)  stage 4 
D)  REM

Sleep Spindles

Bursts of oscillatory brain activity visible on an EEG that occur during stage 2 of NREM sleep, implicated in sleep maintenance and memory consolidation.

Stage 2 Sleep

A phase of sleep characterized by specific brain wave patterns including sleep spindles and K-complexes, representing a deeper sleep than stage 1.

EEG Activity

The recording of electrical activity along the scalp produced by the firing of neurons within the brain, typically referred to as electroencephalography.