~BN20 cortical motor control.ppt

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~BN20 cortical motor control.ppt

  1. 1. Cortical Control of Movement Lecture 20
  2. 2. Hierarchical Control of Movement <ul><li>Association cortices & Basal Ganglia </li></ul><ul><ul><li>strategy : goals & planning </li></ul></ul><ul><ul><li>based on integration of sensory info </li></ul></ul><ul><li>Motor cortex & cerebellum </li></ul><ul><ul><li>tactics: activation of motor programs </li></ul></ul><ul><li>Spinal cord </li></ul><ul><ul><li>execution: activation of alpha motor neurons ~ </li></ul></ul>
  3. 3. Sensorimotor Cortical System <ul><li>Integration of sensory information </li></ul><ul><ul><li>and directed movements </li></ul></ul><ul><li>Anatomy </li></ul><ul><li>Descending spinal tracts </li></ul><ul><ul><li>Lateral pathway </li></ul></ul><ul><ul><ul><li>Pyramidal Motor System </li></ul></ul></ul><ul><ul><li>Ventromedial pathway </li></ul></ul><ul><ul><li>Extrapyramidal pathway ~ </li></ul></ul>
  4. 4. Cortical Anatomy <ul><li>S1 - postcentral gyrus </li></ul><ul><li>PPC - Posterior Parietal Cortex </li></ul><ul><li>M1 - Precentral Gyrus </li></ul><ul><ul><li>Frontal Lobe </li></ul></ul><ul><ul><li>somatotopic organization </li></ul></ul><ul><li>M2 - Secondary Motor Cortex </li></ul><ul><ul><li>SMA - Supplementary Motor Area </li></ul></ul><ul><ul><li>PM - Premotor Cortex ~ </li></ul></ul>M1 SMA S1 PM PPC
  5. 5. M1 S1 PM P r e f r o n t a l Sensorimotor Pathways SMA PPC
  6. 6. Primary Motor Cortex <ul><li>Somatotopic organization </li></ul><ul><ul><li>neurons have preferred direction of movement </li></ul></ul><ul><li>Motor homunculus ~ </li></ul>
  7. 7. M1: Coding Movement <ul><li>Movement for limbs </li></ul><ul><li>Neuron most active </li></ul><ul><ul><li>Preferred direction </li></ul></ul><ul><ul><li>but active at 45  from preferred </li></ul></ul><ul><li>How is direction determined? </li></ul><ul><ul><li>Populations of M1 neurons </li></ul></ul><ul><ul><li>Net activity of neurons with different preferred directions </li></ul></ul><ul><ul><li>vectors ~ </li></ul></ul>
  8. 8. M1: Coding Movement <ul><li>Implications </li></ul><ul><li>1. Most M1 active for every movement </li></ul><ul><li>2. Activity of each neuron 1 “vote” </li></ul><ul><li>3. direction determined by averaging all votes ~ </li></ul>
  9. 9. Motor Association Cortex <ul><li>Motor area other than M1 </li></ul><ul><ul><li>Premotor & Supplemental Motor Areas </li></ul></ul><ul><li>Active during preparation for movement </li></ul><ul><ul><li>Planning of movements </li></ul></ul><ul><li>Stimulation - complex movements </li></ul><ul><ul><li>motor programs </li></ul></ul><ul><li>Active during preparation for movement </li></ul><ul><ul><li>Planning of movements </li></ul></ul><ul><ul><li>e.g. finger movements ~ </li></ul></ul>
  10. 10. Motor Association Cortex <ul><li>Active before movement </li></ul><ul><li>Supplemental Motor Area </li></ul><ul><ul><li>Bilateral lesions  unable to move or speak voluntarily </li></ul></ul><ul><ul><li>Some reflexive movement retained </li></ul></ul><ul><li>Premotor </li></ul><ul><ul><li>Unilateral lesion  impaired stability, gait, hand coordination </li></ul></ul><ul><ul><li>Fine motor control OK ~ </li></ul></ul>
  11. 11. M1 S1 PMA SMA Spinal cord PPC
  12. 12. Planning Movements <ul><li>Targeting vs trigger stimulus </li></ul><ul><ul><li>recording activity of neurons </li></ul></ul><ul><li>active when movement planned </li></ul><ul><ul><li>for specific direction </li></ul></ul><ul><li>Different populations of neurons active </li></ul><ul><ul><li>during planning (targeting) </li></ul></ul><ul><ul><li>& execution (trigger stimulus) ~ </li></ul></ul>
  13. 13. <ul><li>Simple finger flexion </li></ul><ul><ul><li>only M1 activation </li></ul></ul>
  14. 14. <ul><li>Sequence of complex finger movements </li></ul><ul><ul><li>M1 + SMA activation ~ </li></ul></ul>
  15. 15. <ul><li>Mental rehearsal of finger movements </li></ul><ul><ul><li>only SMA activation ~ </li></ul></ul>
  16. 16. The Descending Spinal Tracts
  17. 17. Brain to Spinal Cord <ul><li>Upper motor neurons </li></ul><ul><ul><li>communication with lower (  ) motor neurons </li></ul></ul><ul><li>Lateral pathway </li></ul><ul><ul><li>direct cortical control </li></ul></ul><ul><li>Ventromedial pathway </li></ul><ul><ul><li>brain stem control ~ </li></ul></ul>
  18. 18. The Lateral Pathway <ul><li>Voluntary movement </li></ul><ul><ul><li>distal limbs </li></ul></ul><ul><li>Corticospinal (Pyramidal) tract </li></ul><ul><ul><li>Primary pathway (> 1 million neurons) </li></ul></ul><ul><ul><li>Contralateral control movement </li></ul></ul><ul><li>Cortico-rubrospinal tract </li></ul><ul><ul><li>Via red nucleus </li></ul></ul><ul><ul><li>But some recovery if damage to corticospinal ~ </li></ul></ul>
  19. 19. Spinal Cord: Lateral Pathway Cortico- rubrospinal tract Dorsal Ventral Corticospinal tract
  20. 20. The Ventromedial Pathway <ul><li>Neurons originate in brainstem </li></ul><ul><li>Vestibulospinal & tectospinal tracts </li></ul><ul><ul><li>head & posture posture </li></ul></ul><ul><ul><li>orienting responses </li></ul></ul><ul><li>Pontine & medullary reticulospinal tracts </li></ul><ul><ul><li>originate in reticular formation </li></ul></ul><ul><ul><li>trunk & antigravity leg muscles </li></ul></ul><ul><ul><li>tracts are antagonistic ~ </li></ul></ul>
  21. 21. Major Descending Spinal Tracts Spinal cord Red Nucleus Reticular Nuclei Superior Colliculus vestibular nuclei Ventromedial Lateral Motor Cortex

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