~BN20 cortical motor control.ppt
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~BN20 cortical motor control.ppt

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~BN20 cortical motor control.ppt ~BN20 cortical motor control.ppt Presentation Transcript

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