Why we sleep?


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How sleep affects brain function and how lack of sleep can influence the mind, as in the case of philosopher Emil Cioran, an insomniac.

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Why we sleep?

  1. 1. Why we sleep? Mehdi Tafti [email_address]
  2. 2. Sleep: Behavioral Definition <ul><li>Immobility (rest/activity) </li></ul><ul><li>Stereotypic Posture (place) </li></ul><ul><li>Reduced Response to Stimulation </li></ul><ul><li>Reversibility </li></ul><ul><li>Homeostatically Regulated </li></ul>Torpor-Hibernation, Coma, Altered States
  3. 3. Invention of the Electroencephalogram Hans Berger 1924
  5. 5. The Distribution of Sleep Stages Throughout the Night
  6. 6. Why We Sleep? Francis Crick: &quot;take out the trash&quot; Thomas Edison: “waste of time”
  7. 7. James Horne Oxford University Press 1988 (IBSN 0-19-261682-X) Why We Sleep? *Lack of Stimulation (Sleep = Passive state) *Too Much Stimulation (Wake = Toxic) *For Body Restitution (Metabolism, Energy Conservation) *Brain Restitution (Metabolism, Neural Detoxification) *OTHERS (Brain Plasticity, Genetic Reprogramming,…: State Specific (REM, NREM sleep)
  8. 8. Theories of Sleep: How Nathaniel Kleitman Sleep and Wakefulness University of Chicago Press Midway Reprint Edition 1987 (IBSN 0-226-44073-7) *Neural (Dendritic Theory, Inhibitory, Neural Networks) *Humoral (Instinct, Toxic, Metabolic, Endocrine, Immune) *Sleep/Wake Center (Hypothalamus, Thalamus, RF) *Evolutionary (Sleep/Wake, REM/NREM, Phylogeny )
  9. 9. Sleep Function(s): How to Find Deprivation/Satiation Rechtschaffen Allan et al. 1983 Physiological correlates of prolonged sleep deprivation in rats. Science. 1983 8;221(4606):182-4.
  10. 10. Sleep deprivation in the rat: I. Conceptual issues.Sleep. 1989 12(1):1-4. Sleep deprivation in the rat: II. Methodology.Sleep. 1989 12(1):5-12. Sleep deprivation in the rat: III. Total sleep deprivation.Sleep. 1989 12(1):13-21. Sleep deprivation in the rat: IV. Paradoxical sleep deprivation.Sleep. 1989 12(1):22-30. Sleep deprivation in the rat: V. Energy use and mediation.Sleep. 1989 12(1):31-41. Sleep deprivation in the rat: VI. Skin changes.Sleep. 1989 12(1):42-6. Sleep deprivation in the rat: VII. Immune function.Sleep. 1989 12(1):47-52. Sleep deprivation in the rat: VIII. High EEG amplitude sleep deprivation.Sleep. 1989 12(1):53-9. Sleep deprivation in the rat: IX. Recovery.Sleep. 1989 Feb;12(1):60-7. Sleep deprivation in the rat: X. Integration and discussion of the findings.Sleep. 1989 12(1):68-87. Sleep deprivation in the rat: XI. The effect of guanethidine-induced Sleep. 1990 13(3):218-31. Sleep deprivation in the rat: XII. Effect on ambient temperature choice.Sleep. 1991 14(2):109-15. Sleep deprivation in the rat: XIII. The effect of hypothyroidism.Sleep. 1991 14(3):201-10. Sleep deprivation in the rat: XIV. Comparison of waking hypothalamic.Sleep. 1991 14(4):285-93. Sleep deprivation in the rat: XV. Ambient temperature choice.Sleep. 1992 15(1):13-20. Sleep deprivation in the rat: XVI. Effects in a light-dark cycle.Sleep. 1992 15(6):537-44. Sleep deprivation in the rat: XVII. Effect of aspirin on elevated body. Sleep. 1993 16(3):221-5. Sleep deprivation in the rat: XVIII. Regional brain levels of monoamines.Sleep. 1994 17(7):583-9. Sleep deprivation in the rat: XIX. Effects of thyroxine administration.Sleep. 1995 18(5):317-24. Sleep deprivation in the rat: XX. Differences in wake and sleep.Sleep. 1995 Nov;18(9):797-804. Chronic Sleep Deprivation (Rat): Findings
  11. 11. debilitated appearance skin lesions increased food intake weight loss increased energy expenditure decreased body temperature at late stages of deprivation increased plasma norepinephrine decreased plasma thyroxine Death sleep may be necessary for effective thermoregulation “ Stating that one eats in order not to starve to death or breathes in order not to die of asphyxia, tells nothing concerning the mechanism of hunger or of respiration.” (N. Kleitman, 1969) Sleep Deprivation Syndrome (Rat)
  12. 12. Sleep Deprivation (Humans) *Allen Gilbert (1896)-90h (Recovered 25% of lost sleep) *Randy Gardner (1964)-264h (Recovered 24% of lost sleep) *4 subjects (1966)-205h (Recovered 9% TST, 79% stage 4, 33% REMS) *Walter Reed Experiments (1950s-1960s)-up to 90h
  13. 13. Sleep Deprivation (Humans): Findings J. Horne (1988) *Uneventful for the body (body restitution during wakefulness) *Restoration of cerebral (cortex) function (Behavior and psychological performance) *Cerebral restitution takes place during SWS
  14. 14. State-Specific Functions of Sleep: NREM Sleep *Keeping cool (McGinty D, Szymusiak R, 1990 ) *Cerebral restitution (Homeostasis) -Energy (glycogen: Benington & Heller, 1995) -Plasticity (Neurotrophins, others, unknown) -Synaptic homeostasis (Tononi G, Cirelli C, 2003)
  15. 15. State-Specific Functions of Sleep: REM Sleep *Dreaming (REMS): Self-regulation of the Psyche (Freud, Jung) *Cortical Stimulation (H. Ephron, P.Carrington, 1966) *Sentinel (F. Snyder, 1966) *Ontogenetic (H. Roffwarg et al., 1966) *Motivational (dampened drives; GW. Vogel,1979) *Keeping cold/warm (Thermoregulation) *Genetic Reprogramming of Instinctual Behavior (M. Jouvet, 1980) *Noradrenergic Receptor Sensitivity (J. Siegel, 1988) *Memory Consolidation (or Cleansing), Brain Plasticity Behavioural Brain Research Volume 69, Issues 1-2, Pages 1-210, 1995
  16. 17. Phylogenesis of Sleep Sleep-like state is present in all species PS/REM sleep is present in Birds and Mammals
  17. 18. Sleep Function(s): How to Find *Homeostasis-Molecular Bases (sleep duration/sleep need) Sleep Function(s): Future *Should Explain How and Why *Should Apply to all Species
  18. 19. Sleep as an Adaptive Behavior
  19. 20. &quot;And the Lord God caused a deep sleep to fall upon Adam, and he slept: and he took one of his ribs…” Genesis 2:21 &quot;The Creation of Eve”