Arousal, Sleep, Attention and Selective Engagement

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Arousal, Sleep, Attention and Selective Engagement

• Stephen E. Nadeau, M.D.

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Midbrain Reticular Activating System Arousal

• Projects to intralaminar nuclei of thalamus,
  which send diffuse projections to cerebral
  cortex.
• Projects to relay neurons throughout thalamus.
• Projects to nucleus reticularis, which regulates
  the thalamic gate.

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Figure 12-28
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Nadeau SE, Crosson B. Subcortical aphasia. Brain
Lang 199758355-402, 436-458.
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Major Structures Implicated in Sleep
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12-30
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Disorders of Sleep Architecture

• Narcolepsy (narcolepsy, cataplexy, sleep
  paralysis, hypnogogic/hypnopompic hallucinations)
• Dissociation of REM, dreams, loss of muscle tone
  from normal context
• REM Sleep Behavior Disorder
• No loss of muscle tone during REM
• Night terrors, somnambulism
• REM sleep in wrong context no loss of muscle
  tone
• Non-REM deep sleep deprivation (PLMS, sleep
  apnea) daytime somnolence, loss of concentration
• Fatal familial insomnia persistent wakefulness
• Presumed damage to pre-hypothalamic hypnogenic
  center
• Locked-in state persistent wakefulness
• Damage to caudal pontine hypnogenic center

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Attention Behavior

• Definition focus of sensory resources on a
  particular stimulus
• Reactive
• Superior colliculus (deep layers)
• Temporal and parietal cortex
• Intentional
• Prefrontal cortex
• Orienting response
• Superior colliculus (superficial layers)
• Frontal eye fields (BA 8)

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Hemispatial Neglect

• No response to any left sided stimulus
• L homonymous hemianopia and hemisensory loss
• Hemianopia corrects on right gaze
• Will not look to the left of midline
• Fails to eat from left side of plate or clean
  left side of mouth
• Left hemiparesis in left hemispace

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Figure 12-32
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12-33
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Attention Mechanisms Selective Engagement

• Production of specific patterns of activity or
  neural membrane depolarization in selected
  frontal, temporal, parietal and limbic cortices
• Disengagement of other cortices

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Moran J, Desimone R. Selective attention gates
visual processing in extrastriate cortex. Science
1985229782-784.
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Nadeau SE, Crosson B. Subcortical aphasia. Brain
Lang 199758355-402, 436-458.
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12-34
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Functions of Biogenic Amines

• Acetylcholine declarative and procedural memory
• Dopamine
• Putamenal function regulation of balance between
  direct and indirect basal ganglia pathways
• N accumbens regulation of limbic tone
• Other unknown
• Norepinephrine
• Arousal systems the thalamic gate
• ? Regulation of balance between cortico-cortical
  activity and corticobulbar/corticospinal activity
• ? Regulation of balance between intentional and
  reactive attention
• Other unknown
• Serotonin
• Regulation of balance between orbitofrontal-limbic
  and dorsolateral prefrontal systems
• Other unknown

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Pharmacologic Manipulation of Biogenic Amine
Systems

• Acetylcholine
• Augmentation Acetyl cholinesterase inhibitors
• Blockade scopolamine, Artane, Cogentin,
  Benadryl, tricyclic antidepressants
• Dopamine
• Augmentation levodopa, D2 agonists, cocaine,
  amphetamine
• Blockade neuroleptics
• Norepinephrine
• Augmentation d-amphetamine, methylphenidate,
  tricyclic antidepressants, venlafaxine, cocaine,
  methamphetamine
• Serotonin (5-HT)
• Augmentation tricyclic antidepressants, SSRIs,
  venlafaxine, mirtazapine
• DA, NE, 5-HT
• Depletion reserpine

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Summary

• Arousal MRF
• Sleep
• 5 stages
• Hypnogenic centers (ventral preoptic n., caudal
  pontine reticular formation)
• Arousal centers (MRF ACh tuberomamillary n.
  histamine)
• REM sleep architecture (rostral pontine
  tegmentum)
• Muscle tone (peri-locus ceruleus)
• Disorders of sleep architecture (narcolepsy REM
  sleep behavior disorder night terrors/somnambulis
  m fatal familial insomnia locked in state)

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Summary (cont.)

• Attention
• Focus of sensory resources on one particular
  stimulus
• Reactive
• Intentional
• The orienting response
• Hemispatial neglect a focal disorder of
  attention
• Attention as selective engagement
• Moran and Desimone experiment
• Selective engagement by thalamic biogenic amine
  systems