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Sleep

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  1. Sleep Tony Gardner-Medwin, Physiology room 331 ucgbarg@ucl.ac.uk Slides available at: www.ucl.ac.uk/lapt/med

  2. SUMMARY • Clinical Problems • Characteristics • Changes in CNS • Deprivation • Control • Good textbook: Kandel & Schwartz – Principles of Neural Science • [ But they nearly all are adequate ]

  3. Three conclusions : • Sleep is not 1 state, but 2 radically different states • The brain is not resting, but is active (in altered ways) • The brain is (arguably) conscious, but very poor at remembering what it was experiencing.

  4. Shiftwork, jetlag NARCOLEPSY (sudden daytime sleepiness) & CATAPLEXY (sudden paralysis) Sleep apnoea HYPERSOMNIA (night & day) ?? Some cot deaths? Risk of Death Sleep asthma Principal Clinical Problems associated with sleep INSOMNIA & poor sleep ?? Problems with waking tasks Psychological/ Psychiatric problems

  5. EOG Frontal Parietal Occipital EEG C C Techniques for studying the sleeping brain • Electroencephalogram (EEG) • Invasive recording of ‘field potentials’ summed from many cells • Single cell recording in • unanaesthetised animals (extracellular) • Lesions • Stimulation • Pharmacological intervention • Psychophysics (sensory performance) • PET, MRI yet to have much impact

  6. SWS

  7. Slow Wave Sleep REM/Paradoxical Sleep EEG Large Amplitude Low Amplitude (cf waking) Slow Waves ~ 1 Hz (but theta rhythm in hippocampus) MUSCLES Reduced tone Total relaxation (e.g. in postural & neck muscles) SPINAL Some reduction Strong descending inhibition REFLEXES of motoneurons AROUSAL to ‘significant’ stimuli Raised threshold (deep sleep) but often waking from REM PHASIC Muscle twitches Sudden eye movements (REM) EVENTS Sudden CNS discharges REPORTS ‘dreams’ 0-50% ‘dreams’ 80%-90% ON WAKING & ‘thinking’

  8. Slow Wave Sleep REM/Paradoxical Sleep ……ctd…. REPORTS ‘dreams’ 0-50% ‘dreams’ 80%-90% ON WAKING & ‘thinking’ - but NB poor recall unless immediately after rapid arousal % of SLEEP 60% - 85% ~40% infants ~20% most of life ~15% old age WHEN Initially and in cycles Not initially (except narcoleptics) ~ 90 min cycle

  9. Changes in CNS Activity • Altered neuronal firing patterns & increased synchrony

  10. Single pyramidal tract neuron activity in monkey motor cortex AWAKE SWS REM

  11. Changes in CNS Activity • Altered neuronal firing patterns & increased synchrony • Cutting off sensory inflow, e.g. at LGN

  12. Responses from cat LGN (lateral geniculate nucleus) to 0.1 Hz visual stimulation. Brainstem sectioned. Awake SWS Awake

  13. Changes in CNS Activity • Altered neuronal firing patterns & increased synchrony • Cutting off sensory inflow, e.g. at LGN • Cutting off motor outflow by descending inhibition (NB brainstem lesions and 5HT (serotonin) depleters can prevent this) • Different “connectivity” of brain, e.g. “PGO” waves (Pons – Geniculate – Occiptal cortex) - visual cortex gets signals from the brainstem instead of from the eyes during REM sleep

  14. Activity in cat optic radiation (LGN projection to visual cortex). Awake and in paradoxical (REM) sleep

  15. Optic chiasma Optic radiation LGN Visual cortex

  16. Effects of Total Sleep Deprivation • Decreased sleep latency • Microsleep episodes (& can be EEG slow waves) • Poor performance in long boring tasks (?=2) but short term performance usually normal • Irritability, bizarre statements, paranoia (? ~ cf. schizophrenia) • Increased % of SWS on recovery night (though only <~30% of lost sleep is recovered) • In animals can -> death after ~ 2 weeks, associated with metabolic and immune abnormalities. Effects of REM Deprivation • 1 - 4 above, similar to total sleep deprivation • Becomes difficult to arouse or shift from REM • (5) is opposite: Increased REM on recovery night, and decreased latency to REM • Possible improvement of affect in endogenous depression and bipolar disorder

  17. Arousal and Neuro-modulatory Systems Diffuse projection from RETICULAR ACTIVATING SYSTEM (R.A.S.) -> arousal ‘Specific’ sensory signals to thalamus and cortex ‘Non-specific’ collaterals of sensory axons go to RETICULAR ACTIVATING SYSTEM (R.A.S.) Thalamus • Nuclei of certain known chemical • neuro-modulatory systems • AcetylCholine: Tegmentum [PGO] • Noradrenaline: Locus Coeruleus [Arousal] • 5HT (serotonin): Raphe [Arousal, SWS]

  18. Sleep Tony Gardner-Medwin, Physiology room 331 ucgbarg@ucl.ac.uk www.ucl.ac.uk/lapt/med Please use the Web Discussion Forum for problems/queries