Physiology of Sleep and Dreams :Physiology of Sleep and Dreams


Nature of Sleep and Dreams :Nature of Sleep and Dreams Sleep and dreams as biological rhythms When do people sleep, if they don’t have a clock? Sleep and dreams as physiological states What parts of the brain are active and what parts are inactive during sleep and dreaming Sleep and dreams as drives/instincts What is the purpose of sleep or dreams?


Biological Rhythms :Biological Rhythms Circannual rhythms Bird migration Infradian rhythms Menstrual cycle Circadian rhythms Sleep/wakefulness cycles Entrainment Ultradian rhythms REM/NREM cycles


Circadian Rhythms :Circadian Rhythms Humans, like all mammals, have a 24 hour biological “clock” If people are placed in an environment without any access to daylight, to clocks, or to other markers of time, they follow an activity/rest cycle of about 24.5 hours Shown by Nathaniel Kleitman in a study in Mammoth Cave, Kentucky


Genetics of Biological Clocks :Genetics of Biological Clocks Multiple genes are known to be involved in the clock per (period) tim (timeless) per and tim both have circadian rhythms enter nucleus at night and shut off clock clock starts production of per and tim in nucleus


Entrainment :Entrainment A zeitgeber or timing signal, can reset the clock Sunrise is one signal Changing the time of day of the signal can alter the timing of the biological process


Nathaniel Kleitman (1895-1999) :Nathaniel Kleitman (1895-1999) Kleitman showed people have a biological “clock” Revolutionized study of sleep With Aserinsky, discovered REM sleep in 1953


Control of Cycles :Control of Cycles Sleep/wake cycle and the suprachiasmatic nucleus (SCN) lesions of SCN eliminate sleep/waking cycle REM/NREM cycle and the pontine reticular formation


SCN Control of Circadian Rhythm :SCN Control of Circadian Rhythm


The Cycles of Sleep Stages :The Cycles of Sleep Stages


Control of REM by Pontine Nuclei :Control of REM by Pontine Nuclei


The Description of Brain Waves :The Description of Brain Waves Two parameters frequency the number of waves per second, measured as Hertz, Hz amplitude the height of waves, measured in EEG recordings as microvolts, or V Synchronization synchronized: waves are aligned with each other in time desynchronized: waves occur randomly with each other in time


Physiological Measures :Physiological Measures Brain waves Electroencephalograph (EEG) Beta waves 14 - 30 Hz, <20 V Alpha waves 8 - 13 Hz, 25-100 V Theta waves 4 - 7 Hz, 20 V Delta waves .5 - 4 Hz, 20-200 V Eyemovements Electrooculagraph (EOG) Muscle tension Electromyograph (EMG)


Brain Waves in Sleep :Brain Waves in Sleep Waking low amplitude, high frequency Stage 1 mostly theta waves Stage 2 sleep spindles brief period of high amp,high f K-complex Stage 3 appearance of delta waves Stage 4 (slow wave sleep) mostly delta REM like Stage 1, but with REM


Additional Bodily Changes :Additional Bodily Changes Decreased threshold of awareness of external events Vestibular activation during REM Autonomic arousal in REM Genital arousal in REM


Sleep Disorders :Sleep Disorders Narcolepsy (high levels of REM) Hypersomnia (high levels of NREM) Parasomnias Night terrors Sleepwalking Sleeptalking Insomnias


Narcolepsy :Narcolepsy Clinical symptoms: the narcoleptic tetrad excessive sleepiness during the day cataplexy abrupt loss of muscle tone, without loss of awareness sleep paralysis muscle paralysis of sleep hypnagogic hallucination


Brain Circuits in Narcolepsy :Brain Circuits in Narcolepsy


New Ideas on Narcolepsy :New Ideas on Narcolepsy Animal models Doberman pinschers Neurochemical Basis Defect in Hypocretins or Orexins (HO) Narcoleptic people have little HO Genetic basis Defective gene found in dogs No genetic abnormality in people


Evolution of Sleep :Evolution of Sleep Rest but no sleep amphibians, fish Non-REM sleep only lower reptiles A little REM chameleons, crocodiles, birds (when babies) echidna REM and NonREM All placental mammals


Purpose of Sleep :Purpose of Sleep Excessive sleep deprivation kills rats Sleep deprivation makes people more tired


Development of Sleep :Development of Sleep Babies spend 16 hours sleeping, initially half in REM Over lifespan, total sleep decreases Over lifespan, proportion of REM decreases