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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

An Ultradian rhythm: The stages and cycle of sleep 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.

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.

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

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

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

Getting the whole picture….

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&feat ure=related

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.

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.’  

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.

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

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

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. 

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

Awake A 1 2 3 4 R C

Stage 1 A 1 2 3 4 R C

Stage 2 A 1 2 3 4 R C

Stage 3 A 1 2 3 4 R C

Stage 4 A 1 2 3 4 R C

REM Sleep A 1 2 3 4 R C

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

Sleep Cycles Quality & quantity of sleep diminish with age 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

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

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

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.

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.

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.

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

Exam Question Outline the nature of sleep (8 marks)