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Arousal, Sleep, Attention and Selective Engagement

Arousal, Sleep, Attention and Selective Engagement. Stephen E. Nadeau, M.D. Midbrain Reticular Activating System: Arousal. Projects to intralaminar nuclei of thalamus, which send diffuse projections to cerebral cortex. Projects to relay neurons throughout thalamus.

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Arousal, Sleep, Attention and Selective Engagement

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  1. Arousal, Sleep, Attention and Selective Engagement Stephen E. Nadeau, M.D.

  2. 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.

  3. Figure 12-28

  4. Nadeau SE, Crosson B. Subcortical aphasia. Brain Lang 1997;58:355-402, 436-458.

  5. Major Structures Implicated in Sleep

  6. 12-30

  7. 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

  8. 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)

  9. 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

  10. Figure 12-32

  11. 12-33

  12. 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

  13. Moran J, Desimone R. Selective attention gates visual processing in extrastriate cortex. Science 1985;229:782-784.

  14. Nadeau SE, Crosson B. Subcortical aphasia. Brain Lang 1997;58:355-402, 436-458.

  15. 12-34

  16. 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

  17. 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

  18. 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/somnambulism; fatal familial insomnia; locked in state)

  19. 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

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