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Brain Mechanisms of Movement

Brain Mechanisms of Movement. Lesson 21. Hierarchical Control of Movement. Association cortices & Basal Ganglia strategy : goals & planning based on integration of sensory info Motor cortex & cerebellum tactics: activation of motor programs Spinal cord

tristram-davies
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Brain Mechanisms of Movement

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  1. Brain Mechanisms of Movement Lesson 21

  2. Hierarchical Control of Movement • Association cortices & Basal Ganglia • strategy : goals & planning • based on integration of sensory info • Motor cortex & cerebellum • tactics: activation of motor programs • Spinal cord • execution: activation of alpha motor neurons ~

  3. Cortical Control of Movement • M1 - Precentral Gyrus • Frontal Lobe • somatotopic organization • M2 - Secondary Motor Cortex • SMC - Supplementary Motor Cortex • PM - Premotor Cortex • Somatosensory cortex • S1 - postcentral gyrus • PPC - Posterior Parietal Cortex ~

  4. SMA M1 PPC S1 PM

  5. Sensorimotor Integration • Somatosensory cortex • provides spatial coordinates • Motor Cortex • executes movements • Results in meaningful behavior ~

  6. Motor Association Cortex (M2) • Premotor & Supplemental Motor Cortex • input from S1 & PPC • output to M1 • Active during preparation for movement • Planning of movements • Stimulation - complex movements • motor programs ~

  7. Brain to Spinal Cord • Upper motor neurons • communication with lower (a) motor neurons • Dorsolateral pathway • distal limbs • Ventromedial pathway • trunk, neck & proximal limbs ~

  8. The Dorsolateral Pathway • Voluntary movement • contralateral control • distal limbs • Corticospinal tract • M1  spinal cord • about 1 million axons • Rubrospinal tract • M1  red nucleus  spinal cord ~

  9. Dorsal Dorsolateral tract Ventral Ventromedial tract Descending Motor Pathways

  10. Subcortical Motor Systems:Cerebellum & Basal Ganglia Caudate Putamen Cerebellum

  11. Subcortical Motor Loops • Parallel processing • Cortex  Subcortex  Cortex  Spinal cord • Cerebellum • coordination of movement • Basal Ganglia • selection & initiation of voluntary movements ~

  12. Cerebellum • Coordination of complex movements • Programs ballistic movements • no feedback during execution • direction, force, & timing • Motor learning • shift from conscious  unconscious • Long-term depression (LTD) • inhibits incorrect movements ~

  13. Cerebellum: Damage • Lesions - loss of motor coordination • Dysynergia • no simultaneous movement of joints • serial movement only • Dysmetric movements • to wrong coordinates • Alcohol intoxication • depression of cerebellar circuits ~

  14. Caudate nucleusPutamen Globus Pallidus Substantia Nigra Tegmentum Control slow movements Using immediate sensory feedback ~ Striatum Basal Ganglia

  15. Parkinson’s Disease • 1% of population • Nigrostriatal pathway • Substantia nigra neurons die • Progressive loss • Hypokinesia • Rigidity • Bradykinesia • Akinesia ~

  16. + Striatum DA Substantia Nigra Parkinson’s Disease Motor Cortex +

  17. Parkinson’s Disease: Treatment • Basal Ganglia - Cholinergic • Substantia Nigra - Dopaminergic • Drug Therapy • L-DOPA • Pallidectomy • Tissue transplants ~

  18. Huntington’s Disease (Chorea) • Rare genetic disorder • Single dominant gene on chromosome 4 • onset 30-40s • Symptoms • Uncontrollable, jerky movements • dementia • Progressive ~

  19. Huntington’s Disease (Chorea) • Degeneration of Striatum • Caudate & Putamen • GABA & ACh neurons • Loss of inhibition • over-stimulation of motor cortex ~

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