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Lecture 11


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Rutsuko Ito

lec11 sleep and wakefulness 1. will not be tested on content of pages 590-593 sleep 2. reversible state 3. always do wake up 4. state that is characterized by a reduced responsiveness to the environment 5. spend 30% of our lives sleeping 6. functional significance 7. sleep issues a. prevalent medical problem 8. sleep deprivation a. is it about amount of sleep or quality of sleep? 9. only occurs in higher vertebrate a. exception* sleep in invertebrates 1. invertebrates display modes of sleep 2. disruption of sleep in these invertebrates 3. resulted in compensatory activity 4. activity level over 12 hour period  rest period in normal condition a. if rest is disturbed i. increased amount of resting during subsequent active period behavioral correlates of sleep 1. stereotypic postures of sleep 2. minimal movement 3. no response to external stimuli 4. aspect of reversibility 5. disruption of sleep leads to compensatory activity a. effect of sleep deprivation on behavior conclusion 1. sleep is not the simple uniform suspension of activity 2. highly organized pattern of physiological state 3. important function on its own measuring sleep 1. EEG to measure sleep a. measures general activity in the cortex (superficial areas) b. infer activity in the cerebral cortex but not deeper structure c. also used to diagnose sleep related disruptions d. measuring voltage differences from two points in a cell i. e.g. point in central area vs temporal area EEG 2. measuring synaptic currents in the pyramidal cells 3. when we see EEG trace, we can infer synchronous activity between different neurons 4. neurons 1-6 a. if they are firing together  results in a larger more uniform EEG signal b. the larger the EEG waves, the more the neurons are firing together in synchrony c. this is a state that we can record in deep sleep i. large synchronous delta waves firing d. awake sleep i. neurons firing at different time points and phases ii. no synchrony firing between them iii. produce very small regular waves in the aggregate iv. called alpha waves sleep cycles - functional states 1. identify at least 5 different stages of sleep a. REM sleep b. non-REM sleep i. stage 1 ii. stage 2 iii. stage 3 iv. stage 4 EEG rhythms during sleep 2. wakefulness a. alpha 3. during non REM sleep 1 a. theta 4. stage 2 a. spindle / K complex waves 5. stage 3 6. stage 4 a. deeper, higher amplitude delta waves b. important stage 7. REM sleep a. beta forms of EEG features of sleep cycle 1. think of each cycle as going through the whole complete cycle of being awake and ending with REM a. every 90-100 minutes of sleep 2. ultradian rhythms different from circadian rhythms 3. first two cycles a. 75% non-REM / 25% REM 4. second two cycles a. REM increases in frequency 5. dreams happen most frequently in REM sleep a. characterized by a state of paralysis 6. non-REM sleep  movable body a. hard to wake someone up during stage 4 of sleep b. but body is still able move i. sleep walking what does the EEG / brain rhythms tell us? 1. correlative measures that something is happening a. will not tell us what is happening, but tells us that something is happening changing sleep patterns with age 2. children spend more time in deep stages of sleep 3. elderly spend less time in deep stages of sleep a. shorter periods of REM sleep sleep patterns in schizophrenics 1. reduced sleep in deep stages a. missing stage 4 sleeps alltogether b. shorter REM sleep physiological changes during sleep 2. increased sympathetic activity a. a lot of eye movement b. increased heart rate c. increased respiratory rate 3. what does this mean? a. may be important in dreams mechanisms of sleep 1. two opposing mechanisms that regulate sleep a. circadian driven rhythm b. homeostatic drive for sleep i. the longer we are awake  the more we are inclined to want to sleep circadian rhythms 2. behaviors under regulation of circadian rhythms 3. growth hormone increases during sleep a. important that children need sleep in order to grow 4. many bodily functions regulated by circadian rhythms 5. manipulated by the day / night cycles 6. even without these timing regulations (day / night) a. circadian rhythms are still controlling sleep i. increase in duration of circadian rhythms 1. e.g. people isolated in caves a. settled into 32 hour cycle i. 20 hours awake, 12 hours of sleep changes before sleep 1. melatonin a. increased  induces state of sleepiness b. under control of circadian rhythms c. just before sleep  melatonin increases i. drop in core body temperature ii. increased sleepiness 1. results in sleep d. prescribed to help you to sleep circadian drive for wakefulness 1. goes in a cycle neural substrate for circadian pacemaker? 2. what maintains these rhythms in our bodies? a. most plausible substrate i. suprachiasmatic nucleus 1. termed the brain clock neural basis of sleep regulation 1. each neuron fires at a particular point in a 24 hour cycle a. SCN neuron fires at a specific period during a 24 hour cycle b. different SCN neurons firing at a different time point in a 24 hour cycle c. what is interesting i. block action potentials in SCN neurons 1. expect a. total abolishment of firing of SCN neurons 2. result a. when blocker is removed i. action potentials return at the same rhythm as when it was abolished ii. does not disrupt the rhythm itself b. how does the SCN do this? SCN connectivity 1. discovered special type of ganglion cells in the retina that are photosensitive a. pRGC i. connect directly onto the SCN to entrain the SCN onto light / dark cycles ii. i.e. it is the input to the SCN b. output i. SCN has influence on the neurons that affect the bodily functions 1. e.g.
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