The nature of sleep

Question 1

Electroencephalograph (EEG)

Answer 1

A recording of the electrical activity of the brain. Electrodes on the scalp pick up electrical activity from the millions of neurons in the brain. Different patterns of EEG activity represents different brain states.

Question 2

Desynchronized EEG

Answer 2

A reading with no regular pattern of electrical activity. Usually recorded when the brain is an active and aroused state.

Question 3

Synchronized EEG

Answer 3

A reading that has a regular pattern of electrical activity. The pattern consists of repeated waves with a certain frequency and amplitude. An example of when this can be recorded is in deep sleep (larger and slower).

Question 4

NREM stages of sleep

Answer 4

NREM stages of sleep uses significantly less energy than REM and it is when we fall deeper asleep and the waves seen in the synchronized EEG become larger and slower.
Stage 1 - EEG characterized by theta waves
Short period of sleep
Slowed down heartbeat, breathing and eye movement Relaxed muscles with occasional twitches.
Stage 2 - EEG dominated by theta waves
Bursts of sleep spindles (high frequency electrical activity)
Heartbeat and breathing slow down even further
Brain wave activity slows
Body temperature drops
Eye movement stops
Stage 3 - Delta waves (larger amplitude)
Period of deep sleep.
Occurs in longer than periods during the first half of the night.
Heartbeat and breathing slow down to their lowest
Muscles are relaxed and may be difficult to wake the person up
Brain waves are even slower

Question 5

REM sleep

Answer 5

First occurs about 90 minutes after falling asleep
Delta waves occur
It is in this stage that most of our dreaming occur (Aserinsky and Kleitman 1953)
Rapid eye movement
Faster and irregular breathing
Heart rate and blood pressure increase to near waking levels
Brain activity becomes closer to that seen in wakefulness
Paralysis of the skeletal movements, this prevents us from acting out dreams.