Unit 3 Psychology RAH

NREM Sleep (non rapid eye movement sleep) REM Sleep (rapid eye movement sleep)

These occur in continuous cycles, with one following the other.

In adults, one cycle of NREM sleep last for about 70 to 90 and consists of 4 distinct stages (identified by different brain wave patterns).

REM follows each period of NREM sleep. A complete sleep cycle last for about 80 to 120

minutes and we repeat if 4 or 5 times during 8 hours of sleep.

Approx 80% of our sleep time is NREM.

Brain active during NREM

Believed that it is the time when the body recovers: Repairing body tissue Removing waste products Replenishing

neurotransmitters E.g. Increase in deep

sleep experienced in NREM after vigorous exercise.

NREM consists of 4 stages from light sleep to the stage of deepest sleep and back to light sleep.

Every stage is dominated by a particular brain wave pattern.

Frequency Number of brain waves

Amplitude Intensity of brain wave

Transition period from being awake to being asleep.

May last a minute or 2. People may experience:

Flashes of light or colour Floating or weightlessness Dreamlike images Swift jerky movements Sense of falling or slipping

Occurs as we drift into and out of a true sleep state.

Physiological changes: Decrease in heart rate Respiration Body temp Muscle tension

Hypnic Jerk: muscles relaxing can result in ‘jerking’ (spasm).

Decrease in alpha waves and replaced by theta waves.

Lasts for about 5-10 minutes.

Light stage of sleep. Point where you are

truly asleep. Easily awakened. Lasts approx 20 mins. Body movements

lessen. Temp continues to

fall. Heart rate slower. Mainly theta waves.

Sleep spindles: Brief bursts of higher

frequency of brain wave activity.

An indicator that a person is truly asleep.

Brain still responds to various external and internal stimuli, e.g. someone entering the room.

This stage is still considered to be light.

Start of deepest period of sleep.

Referred to as moderately deep sleep.

Heart rate, blood pressure and body temp continue to drop, breathing continues to be slow and steady.

Relaxed and less responsive.

Delta waves begin to appear.

Slow large, regular, brain waves.

Slow waves sleep (SWS). Generally begins ½ hour

into sleep.

When EEG recordings show that delta waves comprise more than 50% of the brain wave activity, the person has entered stage 4.

Deepest stage of sleep. Very deep sleep. Muscles completely

relaxed. Delta waves dominate. Difficult to wake person. Sleep inertia – post

awakening mental lag. 1st cycle – 20mins. As night progresses, less

and less time is spent in stages 3&4.

Sleep walking, sleep talking and night terrors (and bedwetting) occur.

NREM cycle from stage 1-4 takes about 45-60 minutes.

We then move progressively up through stages 3,2 and 1.

Our brain and body respond as if we are at the point of waking up.

These are signs of moving into REM.

Period of Rapid Eye Movement sleep during which the eyeballs rapidly move beneath the closed eyelids.

Brain wave pattern is irregular.

Low amp/high frequency beta waves.

REM considered to be deep sleep, as people are difficult to wake during this period.

Internal functioning more active during REM the during NREM.

Heart faster and more irregular.

Blood pressure rises. Breathing faster and

more irregular. Yet, sleeper is totally

relaxed.

Also called paradoxical sleep – internally, the brain and body are active, yet body appears calm and inactive.

Most dreaming occurs during REM.

Research suggest we dream several times a night.

Specific movements for eye movements is unclear.

It’s believe to be related to physiological activity that is occurring at the same time as random, neural activity of the brain.

Purpose of REM unclear.

Some research suggests that REM assists in consolidating of embedding new memories in the brain by strengthening newly formed neural connections.

General agreement that REM probably serves some biological need.

Throughout the night, we pass continuously through NREM and REM sleep cycles, with REM periods lengthening and occurring closer together as the night progresses.