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Sleep Tony Gardner-Medwin, Physiology room 331 ucgbarg@ucl.ac.uk Slides available at: www.ucl.ac.uk/lapt/med SUMMARY Clinical Problems Characteristics Changes in CNS Deprivation Control Good textbook: Kandel & Schwartz – Principles of Neural Science

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sleep

Sleep

Tony Gardner-Medwin,

Physiology room 331

ucgbarg@ucl.ac.uk

Slides available at:

www.ucl.ac.uk/lapt/med

slide2

SUMMARY

  • Clinical Problems
  • Characteristics
  • Changes in CNS
  • Deprivation
  • Control
  • Good textbook: Kandel & Schwartz – Principles of Neural Science
  • [ But they nearly all are adequate ]
slide3

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.
slide4

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

slide5

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
slide7

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’

slide8

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

slide9

Changes in CNS Activity

  • Altered neuronal firing patterns & increased synchrony
slide11

Changes in CNS Activity

  • Altered neuronal firing patterns & increased synchrony
  • Cutting off sensory inflow, e.g. at LGN
slide12

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

Awake

SWS

Awake

slide13

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

slide14

Activity in cat optic radiation (LGN projection to visual cortex).

Awake and in paradoxical (REM) sleep

slide15

Optic chiasma

Optic radiation

LGN

Visual cortex

slide16

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
slide17

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]
sleep20

Sleep

Tony Gardner-Medwin,

Physiology room 331

ucgbarg@ucl.ac.uk

www.ucl.ac.uk/lapt/med

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