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The nature of sleep

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 ________ _________.

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The nature of sleep

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  1. The nature of sleep

  2. 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.

  3. Two Toed Sloth – 20 hours If all animals sleep, what does this tell us? Giraffe – 3 hours

  4. Glossary Frequency Amplitude

  5. 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

  6. Glossary Desynchronised EEG A reading that has no regular pattern of electrical activity. This is typically recorded when brain is active. Synchronised EEG A reading that has a regular pattern of electrical activity. Repeated waves with a particular amplitude and frequency. Sleep Spindles Bursts of high-frequency (12-16 Hz) electrical Activity seen in deeper stages of NREM. Delta Waves Seen in EEG in deeper stages of NREM. Large amplitude and a frequency of about 1-4 Hz.

  7. 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

  8. 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 rhyme That will help you remember?

  9. The nature of sleep

  10. 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

  11. Research Jouvet (1969) Found that the control of REM and NREM lies in the ascending reticular formation (a network of millions of neurons buried deep in the brain). Jouvet used techniques such as lesions and electrical stimulation of the brain and found the two critical areas of the brain are: NREM – raphe nuclei REM – locus coeruleus In addition, he found that certain neurotransmitters were involved in Different stages: NREM – serotonin REM - noradrenaline Would you say this is reductionist?

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

  13. *Make into a mind map Evaluation of cycles of sleep Objective 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. Universality There 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. Artificiality of sleep laboratory The 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. Individual differences Most 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.

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