sleep and dreaming

• Sleep


  A natural periodic state of rest for mind + body, in which eyes usually close + consciousness is completely / partially lost, so that there is a decrease in bodily movement + responsiveness to external stimuli
• We spend 1/3 of our lives asleep
• The average person will spend 25 years of their life asleep
• What happens if we don't sleep

  • Logic + reasoning affected
  • Difficulty concentrating
  • Memory problems
  • Depression + anxiety
  • General paranoia
  • Hallucinations
  • Increased risk of various medical conditions e.g. heart disease, diabetes, obesity
• Sleep is an active NOT a passive behavior
• Examples of sleep deprivation


  • Peter Tripp 1959 - 200 hour wakeathon on American radio, began to hallucinate
  • Randy Gardner 1960s - Set out to break world record for longest time spent awake (11days), experienced contracted problems with his eyesight, speech + memory problems, started to hallucinate towards end of experiment
• Evolutionary theories of why we sleep

  • All animals sleep so it must have some valuable function (survival of the species), energy conservation, predator avoidance
• Restoration theories of why we sleep

  • Repair + restore brain (e.g. growth hormones released) + body (e.g. repair muscle tissue)
• Brain processing + memory consolidation theories of why we sleep

  • People need sleep to process information acquired during day, transform information into long-term memory
• Circadian rhythms


  Biological rhythms that last 24 hours
• Ultradian rhythms


  Biological rhythms that last less than 24 hours
• Infradian rhythms


  Biological rhythms that last 1 month
• Ultradian rhythm


  Best example is sleep cycle, biological rhythms that last less than 24 hours
• The sleep cycle has 4 stages and repeats every 90 minutes when sleeping without interruption
• The electroencephalogram (EEG) measures electrical brain activity

  
• The electrooculogram (EOG) measures eye movement
• The electromyogram (EMG) measures muscle tension
• Siffre study


  French cave explorer Michel Siffre spent over six months living in a cave in Texas, deep under the ground, with no light, or anything else to tell him what time of day it was. His biological clock was allowed to 'free-run', that is, he just followed his body's inclinations, eating and sleeping whenever he chose, with no fixed timetable. He had a fairly erratic sleep-wake pattern at first, but it settled down to a pattern that averaged just over 25 hours, instead of 24 hours. This suggests an internal mechanism must regulate our sleep/wake cycle, but it shifts to a length of approximately 25 hours if we do not have external zeitgebers to reset it
• It is difficult to investigate sleep and dreaming because if you're asleep you cannot communicate with the researcher, and even when we wake up only data comes from a self report as only the participant can tell you what they were dreaming about
• Through use of EEGs and EOGs we can study dreams + sleep more scientifically
• Sleep has only relatively recently been researched and understood
• We now know we sleep in stages, and we now know at which stage we're dreaming
• The brain become highly active during sleep, far from being static
• Most of the work undertaken on sleep has been carried out in sleep labs, where the sleeper is wired up to a series of recording instruments - the EEG, EMG and EOG
• Electroencephalogram (EEG)


  Records brain activity / waves

  
• Electrooculogram (EOG)


  Records eye activity
• Electromyogram (EMG)


  Records muscle activity
• REM sleep


  Part of the sleep cycle with rapid eye movements caused by the eyes moving a lot behind the eyelids when dreaming occurs
• Sleep cycle


  A nightly pattern of deep sleep, light sleep and dreaming
• NREM sleep


  Non-rapid eye movement sleep
• Sensory blockade


  When all incoming sensory information is blocked during REM sleep
• Movement inhibition


  When movement is prevented in REM sleep
• Sleep deprivation


  Not having enough sleep, can affect physical functioning such as weight and brain functioning
• Stage 1: sleep onset

  Light sleep, easily woken, slow eye movements, twitching, alpha and theta brain waves
• Stage 2: late night stage


  Brainwaves are slower, mainly delta waves, eye movements stop, bursts of brain activity (spindles), body temperature drops, heart rate slows, moves from light sleep into sleep
• Stage 3: deep sleep

  Almost all slow delta waves, deep sleep, no eye movement, very disoriented when woken up, children may experience sleepwalking or night terrors
• REM sleep


  Approx. 2 hours each night, eyes flicker quickly, dreaming occurs, sensory blockade, starts with signals in the PONS at the base of the brain which shuts off neurons in the spinal cord, preventing movement, rapid, shallow, irregular breathing, eyes jerking, muscles paralysed, heart rate and blood pressure rise
• Sleep cycles last approximately 90 minutes, the first cycle has a short REM period + more deep sleep, as cycles progress, REM sleep gets longer + there is less deep sleep, towards morning we are mostly in light sleep or REM sleep
• Dreaming


  Throughout history humans have attempted to explain dreaming phenomena, Freud argued the function of dreaming was to preserve sleep by unconsciously fulfilling wishes which would otherwise upset + therefore disturb sleeper, recent explanations take a physiological approach - dreams might be explained as result of random firing of neurons which create an image which we then put meaning to
• Research has repeatedly found a correlation between dreaming + brain activity, suggesting a physiological explanation for dreaming