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Sapolsky 11: Stress and a Good Night s Sleep

Endogenous circadian rhythms rhythms that last about a day humans' last around 24.2 h Examples:-activity-temperature-waking and sleeping-secretion of hormones-eating and drinking. Circadian Rhythms. Suprachiasmatic Nucleus (SCN). SCN - main control centerfor sleep and temperaturecircadian rhythms.

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Sapolsky 11: Stress and a Good Night s Sleep

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    13. After 11 days of total sleep deprivation

    14. So, what goes on in the brain in SWS? Areas that ? arousal shut down. Primary sensory areas also shut down. Areas involved in memory consolidation and retrieval don’t shut down, but are isolated from sensory input.

    15. So, what goes on in the brain in REM? INCREASE in sensory integration, motor, limbic, & memory areas. Why don’t we move, if motor areas are activated? One brain area sends inhibitory input to the spinal cord to prevent movement. Frontal cortex shuts down, disinhibiting limbic system.

    16. Reticular formation (red) wakes the brain. Locus coeruleus (blue) inhibits muscles. Basal forebrain (yellow) ? SWS.

    17. Why Sleep? Repair and Restoration Theory Sleep enables the body and brain to repair itself after working hard all day Brain is ~3% of total body weight, but uses almost Ľ of the energy. Going without sleep causes people to be irritable, dizzy, and to have hallucinations and impaired concentration Sleep-deprived rats’ bodies work harder BUT, how much we sleep does not depend on how much we worked that day

    18. Why Sleep?

    19. Why Dream? Facilitate problem solving Facilitate memory consolidation Lots of REM sleep predicts better consolidation of emotional information. Lots of SWS predicts better consolidation of motor tasks. Lots of SWS+REM predicts better consolidation of perceptual information. Patterns of activation of hippocampal neurons are repeated

    20. Sleep deprivation as a stressor Hypothalamic corticotropin INHIBITING factor (CIF) ? SWS ~I hr before waking: CRH, ACTH, and GCs rise and ? waking. If you don’t get enough sleep: decline in stress hormones doesn’t occur. In fact, stress hormones increase. If sleep-deprived, frontal cortex and other areas work overtime: “a bunch of unshaven gibbering neurons counting on their toes, having to ask the rest of their cortical buddies to help out with this tough math problem.””

    21. Sleep deprivation as a stressor Airline flight attendants: 5 vs. 15 days between transcontinental flights. Attendants for airline with 5 day interval had smaller temporal lobes, impaired explicit memory, higher GCs.

    22. Stress as a disruptor of sleep CRH suppresses sleep “throws ice water on those happily dozing neurons” Direct effect on neurons Also via SNS Inhibits mostly SWS, which is needed more than more shallow stages. GCs impair memory consolidation. Random wakening ? higher CGs than predictable awakening: “a sleeping brain is still a working brain.”

    23. Summary SCN is “biological clock” A “Zeitgeber” is a regular stimulus that entrains the circadian rhythm. 90-minute cycles of 4 stages of SWS (1 through 4 and back) plus REM. Sleep deprivation ? increases in stages 3 & 4 and REM on subsequent nights. The reticular formation in brain stem ? waking. Locus coeruleus inhibits spinal motor neurons Basal forebrain ? SWS

    24. Summary Memory consolidation occurs during sleep Emotional memories during REM Motor memories during SWS Perceptual memories during both SWS & REM Corticotropin INHIBITING factor (CIF) may ? SWS CRH decreases sleep Sleep deprivation ? increased GCs and INCREASES cortical activity (inefficient).

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