The nature of sleep

Link to Biological Rhythms

• Sleep wake cycle is a _________ rhythm• This is controlled by endogenous

pacemakers such as the ________.• It is fine tuned by external sources

otherwise known as ________ _________.

• Sleep cycle becomes an ultradian rhythm when we look at the changes within the stage.

Two Toed Sloth – 20 hours

Giraffe – 3 hours

If all animals sleep, what does this tell us?

GlossaryFrequency

Amplitude

The nature of sleep

What does EEG stand for?

What does it allow us to measure?

What are the two main classes of sleep as identified by Aserinsky and Kleitmen (1953)?

* Show slideshow EEG

GlossaryDesynchronised EEGA reading that has no regular patternof electrical activity. This is typically recorded when brain is active.

Synchronised EEGA reading that has a regular patternof electrical activity. Repeated waves with a particular amplitude and frequency.

Sleep SpindlesBursts of high-frequency (12-16 Hz) electricalActivity seen in deeper stages of NREM.

Delta WavesSeen in EEG in deeper stages of NREM.Large amplitude and a frequency of about1-4 Hz.

Up and down the “sleep escalator”

• Most people have 5 cycles of sleep a night that last approximately 90 minutes. Slow-wave sleep (SWS) occurs in only the first two cycles; REM sleep occurs in all of the cycles, and increases during the course of the night’s sleep.

• Electroencephalographs (EEGs) measure electrical activity or brain waves, electro-oculograms (EOGs) measure eye movement, and electromyograms (EMGs) measure muscle movement and have been used to distinguish the stages and cycles of sleep. EEG readings are normally used as frequency and amplitude differ depending on the stage.

• Traditionally, self-report data was used before the development of the recording technology

Up and down the “sleep escalator”• 1, 2, 3, 4, 3, 2, REM• 2, 3, 4, REM• 2, REM• 2, REM• 2, REM

• 10, 10, 40, 60 (for how long the REM cycles are)

Can you think of a rhymeThat will help you remember?

The nature of sleepNREM – Slow Wave Sleep (SWS)Stage 1 and 2 Hypnogogic

Heart beat

Waves

Spindles

Frequency & Amplitude

Stage 3 and 4 Waves

Frequency & Amplitude

REM

REM Paradoxical

Eyes

Motor

Frequency & Amplitude

Sleep stages

• Dement and Kleitman (1957) demonstrated a link between REM sleep and dreaming.

• How do you think they measured this?• They woke participants up at times when their

brain waves were characteristic of REM sleep and found that Ps were highly likely to report dreaming.

• However – dreaming was also reported outside of REM sleep

• What is a problem with this research method?• Correlation – can we establish a cause?• Sample – mostly men and small sample

Research

Jouvet (1969)

Found that the control of REM and NREM lies in the ascendingreticular formation (a network of millions of neurons buried deep in the brain).

Jouvet used techniques such as lesions and electrical stimulation of the brainand found the two critical areas of the brain are:NREM – raphe nucleiREM – locus coeruleus

In addition, he found that certain neurotransmitters were involved inDifferent stages:NREM – serotoninREM - noradrenaline

Would you say this is reductionist?

Task

In continuous prose, write 50-100 words on the differences between slow wave sleep and REM sleep

Evaluation of cycles of sleepObjective evidence EEG, EOG and EMG provide objective measures of sleep – this means they are less subject to bias. Self-report is vulnerable to bias and distortion, due to researcher effects and participant reactivity, therefore it may lack validity.

Artificiality of sleep laboratoryThe sleep lab is an artificial condition and people are “wired up” to machines. The sleep lab is reductionist as it does not reflect many factors that can influence sleep in real life. The research lacks mundane realism and this means that the findings lack generalisability and ecological validity may be lacking.

UniversalityThere are some universal characteristics of sleep as stages 3 and 4 occur only in the 1st two cycles and REM sleep always increases in duration with each successive cycle.

Individual differencesMost people have 5 sleep cycles and sleep for around 8 hours. But many people sleep much less than this and much more. Patterns of sleep vary from each individual.

Weakness of the self-report method. The self-report method yields subjective data compared to the objective measurements of EEG, EOG and EMG.

*Make into a mind map