pathways for motor control and learning. spinal cord: the stretch reflex maintain stability

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  • Pathways for Motor Control and Learning

  • Spinal Cord: The stretch reflexMaintain stability

  • Spinal Cord: The stretch reflexMaintain stabilityBut modifiable: State dependente.g., gait, sharpshooter

  • Spinal Cord: The stretch reflexMaintain stabilityBut modifiable: State dependentMovement as change between postural states.

  • Reflex-like behavior in the right anatomy. Complex behavior

  • Reflex-like behavior in the right anatomy. Complex behavior

  • Central Pattern GeneratorsEvolutionary Learning

  • Rapid modification of ancient CPGChoi and Bastian, 2007Split-belthttp://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S1.mov

  • Rapid modification of ancient CPGChoi and Bastian, 2007Stance Phase Grey: Fast leg Black: Slow legContext-specific adaptation

  • Rapid modification of ancient CPGChoi and Bastian, 2007Split-beltHybrid walking: One leg forward and one leg backwardhttp://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S5.mov

  • Descending Signals: Extrapyramidal PathwaysIntegration of other sensory signals with spinal mechanisms.

  • Subcortical Characters: The CerebellumMultisensory (and other) inputsDescending and ascending output

  • Subcortical Characters: The Basal Ganglia

  • Anatomical features:Multisensory/associative inputComplex internal circuitryRestricted outputReplication of circuitry

  • Motor Cortex

    The Cortex: Primary Motor Cortex

  • Internal capsulePyramidal Tract (corticospinal) 90% Crossed; 10% Uncrossed Project to motor neurons and spinal interneuronsOrigin in M1, premotor, postcentral

  • Premotor Cortex The Cortex: Secondary Motor AreasSupplementary Motor Area (SMA)

  • The Cortex: Association Motor Areas (take that vision chauvinists) Pre-SMA

  • Views on hierarchical organization1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory

  • Views on hierarchical organization1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory2. Flexibility: Contextualization of ActionExploiting degrees of freedom

  • Views on hierarchical organization1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory2. Flexibility: Contextualization of ActionExploiting degrees of freedom3. Abstraction of controlGoal > Action > Movemente.g., reaching for coffee cup

  • Views on hierarchical organization1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory2. Flexibility: Contextualization of ActionExploiting degrees of freedom3. Abstraction of controlGoal > Action > Movemente.g., reaching for coffee cup4. Other ???

  • Motor LearningThree paradigms:Force field learning A: Baseline (null field) B. Force Field C. Initial Perf. D. Late Perf. E. Generated forces, late F. After-effect in null field

  • Motor LearningThree paradigms:Force field learning Visuomotor transformationsDEMO

  • Motor LearningThree paradigms:Force field learning Visuomotor transformationsexamples: displacements, rotations, inversions, reversals (mirror drawing), depth distortions

  • Motor LearningThree paradigms:Force field learningVisuomotor transformationsSequence learning Serial Reaction Time Task Press response key corresponding to stimulus position.Stimuli follow sequence or are chosen at random.

  • Motor LearningThree paradigmsForce field adaptationVisuomotor transformationsSequence learningDoes one term (motor learning) fit all? How to determine similarities/differences?

  • Motor LearningS&Ws (anti)definition: Adaptation vs. SkillsAdaptation: Retuning of existing competence.Regain capabilities in altered circumstances.Skill: Expansion of motor repertoire.

    Force field: Adaptation Sequence learning: Skill Visuomotor transformation: ???

  • Acquisition:error type? on-line vs. knowledge of resultssensory vs. symbolic?rate of learning?

  • Acquisition:error type? rate of learning?Generalizationlocal or general?transfer?SRT is symmetricForce field is better right to leftVMT may be better left to right (?)

  • Acquisition:error type? rate of learning?Generalizationlocal or general?transfer?Consolidation:Stability over time?Does learning related task interfere with initial learning? Would this be characteristic of skill or adaptation?

  • Consolidation in force field learning:B1: Initial force fieldB2: Second force field, learning after delay (consolidation phase)Time-dependent consolidation.Always some interference from B2.Is control correct term? Note that in control, there is an intervening force field the null field of everyday life.

  • Motor LearningThree paradigmsForce field adaptationVisuomotor transformationsSequence learningNeural systems: Do these tasks engage common regions?

    A. SCHWARTZ STATED THAT OF CORTICOSPINAL PATHWAY, ONLY 30% IS FROM M1. 30% IS FROM PREMOTOR AND 30% IS FROM PARIETAL. NEED TO GET REFERENCE FROM HIM ON THIS. Schwartz referred me to Phillips and Porter, 1977. They report the above distribution for monkey but go on to say that in man, current estimate is that 60% of the Fibers originate in M1. see http://motorlab.neurobio.pitt.edu

    Shadmehr J Neurosci, 1997Dependent measure is % improvement in performance at retest compared to intial training.

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