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The Spec

The Spec. Describe the Nature of Sleep (24). Evaluate how appropriate sleep labs are for studying sleep Explain the changes that happen during a nights sleep Identify stages of sleep from an EEG output. A. C. E.

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The Spec

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  1. The Spec

  2. Describe the Nature of Sleep (24) • Evaluate how appropriate sleep labs are for studying sleep • Explain the changes that happen during a nights sleep • Identify stages of sleep from an EEG output A C E

  3. An Ultradian rhythm: The stages and cycle of sleep.   The cycle of sleep typically lasts about 90 minutes and during a typical nights sleep we will repeat this cycle four or five times.

  4. Stages of Sleep • Not much was known until psychologists began to use Electroencephalography (EEG) • Electrodes are attached to the scalp which record electrical activity of the brain. • EEG produces brain waves (on paper or on a computer) that vary in terms of frequency (Hertz) and amplitude (the number of waves per second and the height of the waves.

  5. Stages of sleep – what does your sleep look like on an EEG (electroenchalograph)?

  6. Overview • http://www.youtube.com/watch?v=emvqA-_7BGM

  7. How the Sleep Cycle is measured • 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. • Traditionally, self-report data was used before the development of the recording technology

  8. Getting the whole picture….

  9. Sleep • We sleep 25% of our total lifespan (on average) • 4 successive stages of non-REM (stage 1-4) sleep plus REM sleep – makes up the ultradian rhythm. • Each stage has a distinctive EEG • Investigated mainly in special ‘sleep laboratories’ http://www.youtube.com/watch?v=mNeLuB2KKpY&feature=related

  10. Awake • Awake: The brain is active and shows what is called beta activity (see EEG).  • When we relax, for example close our eyes or meditate the brain shows alpha activity.  These are slower waves with higher amplitude.

  11. Stage 1 (15 minutes) • We often wake from this stage.  • We may wake from this stage and think that we’ve been dreaming known hypnogogic phenomena (fleeting images rather than the bizarre stories)  • The eyes may roll slowly.  Sometimes we may wake without realising that we’ve even nodded off.  • Reductions in heart rate, muscle tension & temperature. – Drowsiness. • Brain waves are slower and are called ‘theta.’  

  12. Stage 2 (20 minutes) • Bursts of high frequency waves called ‘sleep spindles.’  • We are still aware of sounds and activity around us and the brain responds to this with K-complexes.  • At this stage we are still very easily woken.

  13. Stage 3 (15 minutes) • The brain waves start to slow and become higher in amplitude and wavelength known as delta waves and are associated with deep sleep.  • We are now more difficult to wake.  • First time round in the night this stage is brief, only a few minutes, but we spend longer in it later in the night. • breathing deepens, snoring may start

  14. Stage 4 (30 minutes) • More delta waves now constitute most of the brain activity • Most relaxed • very difficult to wake up   • Heart rate and blood pressure fall, muscles are very relaxed and temperature is at its lowest. • We have now been asleep for about an hour.  • We start to ascend back through these stages in reverse order, i.e. back to level 3 and then to level 2.  • Sleepwalking and talking occurs during this stage • However, instead of going back to level 1, after just over an hour we enter REM

  15. REM • (10 minutes at start of night, up to an hour later in the night) • ‘paradoxical sleep.’  • The brain now becomes very active, almost indistinguishable from a waking brain.  • Heart rate and blood pressure increase, as does body temperature, and the eyes twitch rapidly giving this stage its name.  • But, despite this frantic activity the body remains motionless. •  We are paralysed and unable to act out the brain’s bizarre thoughts.  • REM is now thought by some to be the deepest stage of sleep since it is now that we are most difficult to wake up. 

  16. Stages of Sleep: An Ultradian Rhythm http://www.youtube.com/watch?v=uWYwMnMMEoU http://www.youtube.com/watch?v=9VCIY-UvcII&feature=related

  17. Awake A 1 2 3 4 R C

  18. Stage 1 A 1 2 3 4 R C

  19. Stage 2 A 1 2 3 4 R C

  20. Stage 3 A 1 2 3 4 R C

  21. Stage 4 A 1 2 3 4 R C

  22. REM Sleep A 1 2 3 4 R C

  23. REM REM REM REM A St1 St2 St3 St4 A 1 2 3 4 R C

  24. Sleep Cycles • For the first two cycles, people progress down to stage 4, remain there awhile, then return to stage 2 & enter REM In later cycles: • Stage 4 seldom occurs • Amount of REM steadily increases • Most get 1 1/2 hours of REM & Stage 4 per night • Stages are repeated throughout the night 1,2,3,4,5,4,3,2,3,4,5,4,3,2,……. Complete cycle lasts about 90 minutes. Most sleepers complete about 5 Ultradian rhythms during a night’s sleep. With more REM activity with each • Quality & quantity of sleep diminish with age • Stage 4 sleep diminishes the most in older adults

  25. Activity • Use your textbooks and notes to research the different stages and cycles of sleep • Take 10 mins to rehearse the info: talk to a friend about what you have learnt or produce a mindmap. • Close your textbooks and hide your mindmap. • Complete the card sort

  26. Individual differences • The outline above describes a typical or average night’s sleep.  • Large individual differences between people.  Some may sleep much shorter periods, others who have been sleep deprived will spend longer in stage 4 and REM, and the pattern changes with age.  A.I.Ds

  27. Evaluation of the cycles of sleep • Objective evidence – EEG, EOG and EMG provide objective (scientific) 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.

  28. Evaluation of the cycles of sleep • 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.

  29. Evaluation of the cycles of sleep • 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.

  30. Evaluation of the cycles of sleep • 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

  31. Exam Question Outline the nature of sleep (8 marks)

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