PSYC 460 -- Notes on Sleep (Part I) -- Dr. King Slide 2: Sleep: Electrical Signs I. beta activity A. ~20 Hz B. desynchronized, LVF C. awake and alert II. alpha activity A. ~10 Hz B. synchronized, HVS C. resting, inattentive, eyes closed III. theta activity (from the cortex) A. ~5 Hz B. synchronized, HVS C. light sleep, extreme boredom IV. delta activity A. ~2.5 Hz B. synchronized, HVS C. deep slow-wave sleep (SWS) Slide 3: Sleep: Electrical Signs I. the EEG - synchronized during SWS; desynchronized during REM II. the EOG - slow and drifting during SWS; shows rapid eye movements during REM III. the EMG - reduced activity during SWS; very much reduced or absent activity during REM IV. PGO waves (recorded from the LGN) - absent (or rare) during SWS, appear just before the onset of REM Slide 4: A Typical Night's Sleep I. stage 1 - onset of theta II. stage 2 - more theta, spindles, K complexes III. stage 3 - delta < 50% IV. stage 4 - delta > 50% V. REM - rapid eye movements, desychronized EEG (or stage 1-like EEG) Slide 5: The Sleep Cycle * wakefulness - alert and vigilant (beta) or resting with eyes closed (alpha) * stage 1 - theta begins to appear in EEG * Oswald considered this an intermediate state - "borderland" or "hypnagogic" * thinking distorted with bizarre associations and psychotic-like thought patterns * sensory shocks - sudden, momentary sensory and motor phenomena MAY occur * falling sensations - due to sudden muscle relaxation * auditory hallucinations - bells, guitars, breaking glass, voices * unformed visual experiences such as light flashes * hypnagogic hallucinations - formed visual dreams that the sleeper is viewing passively (sometimes persist after waking - a particularly scary one is seeing someone standing next to your bed!) * hypnagogia - the state of consciousness (or experiences) leading to sleep * stage 2 - light sleep; theta increases, sleep spindles, K complexes Slide 6: The Sleep Cycle * stage 3 and 4 - deep SWS sleep * progression to this state normally takes 15-30 min. after falling asleep (sometimes up to an hour) * deep sleep - most difficult to awaken, and awaken groggy and unresponsivie * occurs mostly early in the night * this is where sleepwalking and sleeptalking occur Slide 7: The Sleep Cycle * REM sleep - in humans, detected by a sudden decrease in muscle tension, the appearance of REMS, and a shift to desynchronized EEG * this is when dreaming occurs (or is reported upon awakening) * first episode may last 10 min., but episodes become progressively longer during the night * in an average night there will be 4-5 REM periods - we all dream every night, but some of us don't remember it * also called paradoxical sleep (because of the desynchronized EEG) * the flaccid paralysis of muscles is only partial in humans, but is more complete in animals, which can become quite floppy * penile erection and vaginal moistening occur Slide 8: Sleep is Not a State of Brain Shutdown Slide 9: The Basic Rest-Activity Cycle * Nathaniel Kleitman * the 90-minute cycles seen in SWS/REM alternation are also seen throughout the day in activities like eating, drinking, smoking, performance on cognitive tasks, etc. Slide 10: Changes in REM During the Lifespan Slide 11: Effect of Aging on Sleep Cycles Slide 12: Effect of Depression on Sleep Cycles Slide 13: Mental Activity During Sleep * Are we really "unconscious" during sleep? * during REM sleep * blood flow is high in the visual association cortex * low in the primary visual cortex * lots of activity in motor areas as if the person were actually moving - but these impulses are prevented from reaching the muscles (usually) * brain mechanisms active during a dream are those that would be active if the events of the dream were actually occuring * night terrors, as well as sleep walking and sleep talking, typically occur during SWS Slide 14: Is the Content of Dreams Symbolic? * latent vs. manifest content (Freud) * or is it inherently meaningless random brain activity that the brain then attempts to give some meaning to * Hobson's activation-synthesis theory * dream interpretation may be like a Rorschach test * the content of most dreams is mundane Slide 15: Sleep Disorders * there are large individual differences * some people do fine with 5 hrs. (rarely less) * other people need 9 or even 10 hrs. * people who get about 7 hrs/night seem to live the longest (this does NOT mean you should force yourself to get 7 hrs.) * signs of insufficient or poor quality sleep * difficulty waking up * poor concentration * urge to sleep during the day * feelings of moodiness or depression Slide 16: Sleep Disorders: Insomnia * incidence: 25% occasionally and 9% regularly * forms of insomnia * sleep onset insomnia * sleep maintenance insomnia * early awakening insomnia * pseudoinsomnia * sleep apnea (occasional episodes of apnea during sleep are common and do not constitute a disorder) * fatal familial insomnia - a genetic disease (next) Slide 17: Fatal Familial Insomnia * autosomal dominant gene * found in probably less than 100 families in the world * it's a prion disease related to CJD * average age of onset of symptoms is 50 yrs. * always progresses to a fatal outcome within 1-2 yrs. Slide 18: Causes of Insomnia * irregular sleeping habits * stress, worry * psychological disorders such as depression and anxiety disorders * pain, discomfort, physical ailments * drug dependency insomnia - withdrawal from sleeping medications (iatrogenic) * sleep apnea - throat muscle atonia or obstruction of the throat (usually) Slide 19: Sleep Disorders: Narcolepsy * diagnosed incidence - 1 in 1500-2000 people (maybe 3X that many cases undiagnosed) * a neurological disorder characterized by sleep, or some of its phenomena, at inappropriate times (does NOT include sleeping in class) * sleep attacks - an overwhelming urge to sleep, usually in monotonous situations, and resulting in 2-5 minutes of normal sleep * cataplexy - person collapses into a flaccid paralysis, usually during emotionally arousing situations, but remains aware of his surroundings * sleep paralysis - intrusion of REM paralysis into waking just before or after sleep * hypnagogic hallucinations - intrusion of visual dreaming into waking, usually during episodes of sleep paralysis Slides 20-22: videos of two dogs and a boy with cataplexy Slide 23: a first person description of sleep paralysis Slide 24: Causes of Narcolepsy * in the lateral hypothalamus there is a nucleus of neurons that use a peptide neurotransmitter called hypocretin or orexin - hypocretinergic or orexinergic cells (orexin is coming to be the accepted name) * these cells are activated by environmental events and psychological factors that motivate wakefulness and interfere with sleep * they activate brainstem areas that maintain wakefulness * narcolepsy is due to a deficiency of orexin receptors or of orexin-secreting neurons - due to a genetic disorder, perhaps autoimmune * onset is usually during adolescence, which is when the immune system begins attacking these cells * treatment * Ritalin or similar stimulants for sleep attacks * antidepressants that are both 5-HT and NE agonists are used to treat the REM sleep symptoms Slide 25: various figures Slide 26: Other Sleep Disorders * REM sleep behavior disorder - aka REM without atonia * results in dreams being acted out * presumably due to disruption of functioning of a nucleus in the medulla called the nucleus magnocellularis - associated with neurodegenerative disorders like Parkinson's disease * this is the nucleus that keeps the muscles turned off during REM sleep * so now all that motor activity visible on the scans can be expressed in behavior! * similar disorders can be produced in experimental animals by lesioning this nucleus * absence of REM sleep - at least one person has been discovered who has no REM sleep (doesn't seem to have any ill effects) Slide 27: Other Sleep Disorders * disorders associated with SWS * sleepwalking and sleeptalking * night (sleep) terrors * bed wetting * sleep-related bruxism * sleep-related eating disorder Slide 28: The Functions of Sleep * all vertebrates sleep or become quiescent (enter a sleep-like state) * all warm-blooded vertebrates (birds and mammals) cycle between SWS and REM - which means REM does not have any uniquely human significance * question: What do all birds and mammals have that no other animal has? * answer: a neocortex * some marine mammals (bottlenose dolphins and porpoises) sleep one brain hemisphere at a time Slide 29: Sleep Deprivation Experiments * some early experiments on sleep deprivation (esp. REM deprivation) suggested that prolonged wakefulness could make you psychotic Slide 30-31: Pete Tripp Slide 32: Randy Gardner Slide 33: Sleep Deprivation (cont.) * more recent studies have suggested that the primary (and perhaps only) effect of sleep deprivation is profound sleepiness (sleep does not seem to be necessary for recuperation of the body) * visual effects - visual distortions and "hallucinations" (fog, cobwebs, etc.) * failure of concentration * no serious deterioration in simple mental capabilities - highly motivated subjects do as well as non-sleep-deprived subjects * when people are aroused from SWS, they act groggy and confused, as if the cortex had been shut down and was taking some time to start up again - maybe the function of SWS is to allow the cortex to rest * there is a direct relationship between how much beta an area of cortex displays during wakefulness and how much delta it displays during SWS - "the harder it works, the harder it rests" Slide 34: Sleep Deprivation (cont.) * effects of mental arithmetic * effects on seizure proneness * effects on driving (in a driving simulator) Slide 35: Changes in Brain Activity After Sleep Deprivation * much less activation in the cortex during a mental arithmetic task Slide 36: Functions of SWS * an early theory suggested that SWS had the function of allowing the body to restore itself after a day's wear and tear * evidence - after physical exercise, the amount of SWS increases * but the same effect can be produced by heating the head with a hair dryer * on the other hand, the evidence is good that SWS allows the cortex to rest and recuperate Slide 37: Functions of REM Sleep * Does REM have something to do with brain development? * Animals born with mature brains spend less time in REM than animals born with immature brains. (see figure on this slide) * There has been long-standing speculation that REM sleep has something to do with memory consolidation. * The default theory of REM (Horne) - REM has no useful function other than to be the easiest state of the body to maintain. When wakefulness or SWS is needed, it is produced instead. Slide 38: The REM Rebound * after REM deprivation, once the person is allowed to sleep normally, REM sleep will be increased, as if the brain is attempting to make up lost REM * after total sleep deprivation, SWS is made up first * REM rebound suggests that there is a need for REM sleep and that the amount of REM sleep we get is regulated Slide 39: Sleep and Learning * Evidence is now mounting that sleep plays a role in long-term memory consolidation, and the role of REM and SWS may be different. * explicit (declarative) vs. implicit (nondeclarative or procedural) memory * REM seems to be involved in consolidation of implicit memories. * SWS seems to be involved in consolidation of explicit memories. Slide 40: Next: The Physiology of Sleep