Stages of Sleep

REM - Characteristics

Sleep state - internal functioning is more active but sleeper looks relaxed.

Heart rate - faster and more irregular than NREM.

Eye movement - spontaneous bursts of rapid eye movement.

Muscle tension - occasional twitching but most muscles are limp (appears paralyzed to observers).

REM Functions

= cements information into memory, emotional memories are processed and stored.

REM Length

= 20-25% of total sleep time.

NREM (Stage 1) - Characteristics

Sleep state - low arousal threshold, easily awakened, if awoke in stage 1 may feel as though they haven’t been asleep at all.

Heart rate - decreased heart rate.

Eye movement - slow, rolling eye movements.

Muscle tension - decreased muscle tension.

NREM (Stage 1) - Functions

= transition between wakefulness and sleep.

NREM (Stage 1) - Length

= 4-5% of total sleep time.

REM (Stage 2) - Characteristics

Sleep state - light sleep, higher arousal threshold than stage 1, becomes noticeably deeper half way through this stage.

Heart rate - heart rate continues to decrease.

Eye movement - no eye movements.

Muscle tension - relaxed.

REM (Stage 2) - Functions

= memory consolidation.

REM (Stage 2) - Length

= 45-55% of total sleep time.

REM (Stage 3) - Characteristics

Sleep state - deepest stage of sleep.

Heart rate - lowest and most regular heart rate.

Eye movement - no eye movements.

Muscle tension - completely relaxed.

REM (Stage 3) - Functions

= physical repairs, consolidates declarative memories.

REM (Stage 3) - Length

= 3-15% of total sleep time.