Ultradian rythms- the stages of sleep

What are ultradian rythms?

Rhythms that last less than 24 hrs and repeat multiple times a day

What are Electroencephalogram brainaves?

• A non invasive method of recording the brain’s electrical activity

• Uses electrodes placed on the scalp to detect the firing of neurons in the cerebral cortex

• Produces a graphical output of brainwave patterns

• Frequency- how close the wavs are to each other (waves per second in Hz)

• Amplitude- the size of the brain wave (change in voltage)

• Five distinctive patterns are delta, theta, alpha, beta and gamma

What are the stages of sleep

• Four stages of sleep

• Stages 1-3 are REM (rapid eye movement sleep) or NREM- called N1, N2 and N3

• After passing back through N2 and N1

• Stage 4 is REM sleep, most dreams occur in REM

• Once cycle takes about 90 minutes and repeats 4-5 times over the course of a night’s sleep

Stages of sleep: N1- light sleep

• NREM

• The transition between wakefulness and sleep

• Easy to wake and the body may move (hypnic jerks)

• There may be a sensation of falling, mild auditory or visual hallucinations (hypnagogic hallucinations)

• EEG’s show theta waves, slow frequency but high amplitude in comparison to awake

Stages of sleep: N2- deeper sleep

• NREM

• N2 is deeper than N1, harder to wake, the body is relaxed, heart and body temp are lowered and eyes are still

• EEG shoes slow theta waves but occasional activity called sleep spindles( short bursts of rapid brain activity) and K complexes (sharp, high amplitude waves)

Stages of sleep: N3- deepest sleep

• NREM

• Deepest sleep stage

• Very difficult to wake, body at its most relaxed with heart0rate at its lowest

• Identified on the EEG by the presence of slow frequently and large amplitude delta waves (slow wave sleep)

Stages of sleep- REM

• REM

• Brain returns to active state passing back through N2 and N1

• REM is similar to wakefulness as seen on the EEG however the body is paralysed

• Looks like beta waves on the EEG

• Characterised by rapid eye movement, and associated with dreaming as when woken, people will report vivid dreams in this stage

• The brain returns to N1 after REM, repeating the cycle up to 5 times in one night

• Each cycle tends to include a larger proportion of REM sleep and shorter duration of N3

Research on the stages of sleep

• Dermot and Kleiitman (1957)

• Study 1- EEG recordings of 33 ppts over a night sleep- brain waves showed a cyclic pattern of activation with bodily relaxation occurring during slow wave sleep and REM during periods of high activation

• Study 2- 9 ppts woken up at different stages in their sleep cycle reported dreaming more frequently when woken in REM stage

• Shapiro (1981)- Ultramarathon runners showed longer sleep after intense physical activity- also an increased proportion in slow wave sleep- suggesting N3 is for the physical recovery of the body

• Haider (1970)- EEG of 10 patients recovering from their drug overdose showed increased REM sleep, suggesting REM sleep is for mental recovery

Evaluating the Ultradian rhythm

• Technology and devices based on understanding sleep have been developed- help improve individuals sleep- leads to people feeling less groggy and disoriented- happier, healthier and more economically productive population- real life application and positive economic implications

• The development of more sophisticated EEG’s and other techniques helps further understanding of the sleep cycle- leading in 2007 stages 3 and 4 being combined into the new N3 stage

• Circadian and ultradian rhythms seem t be connected and perhaps shouldn’t be seen as a separate process- Czeisler (1980) showed the longest period of REM occurs at the lowest point in the CR temp cycle- could mean both process use the same endogenous pacemaker

• Overall patterns of sleep stages is consistent however there are some individual differences with newborns spending 80% of sleep in REE, compared to 2-25% in adults- suggests the stages of sleep are not a simple process but adapt to the developmental needs of the individual

• Lab studies may lack eco val- may not reflect the natural bodily relaxation at home- not a natural environment