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 reflex
Maintain stability
Spinal Cord: The stretch reflex
Maintain stability
But modifiable: State dependent
e.g., gait, sharpshooter
Spinal Cord: The stretch reflex
Maintain stability
But modifiable: State dependent
Movement 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 Generators
Evolutionary Learning
Rapid modification of “ancient” CPG
Choi and Bastian, 2007
Split-belt
http://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S1.mov
Rapid modification of “ancient” CPG
Choi and Bastian, 2007
Stance Phase Grey: Fast leg Black: Slow leg
Context-specific adaptation
Rapid modification of “ancient” CPG
Choi and Bastian, 2007
Split-belt
Hybrid walking: One leg forward and one leg backward
http://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S5.mov
Descending Signals: Extrapyramidal Pathways
Integration of other sensory signals with spinal mechanisms.
Subcortical Characters: The Cerebellum
Multisensory (and other) inputs
Descending and ascending output
Striatum
Globus Pallidus
Subthalamic nucleus
Substantia nigra
Components of the Basal Ganglia
Subcortical Characters: The Basal Ganglia
Anatomical features:Multisensory/associative input Complex internal circuitry Restricted output
Replication of circuitry
Motor Cortex
The Cortex: Primary Motor Cortex
Internal capsule
Pyramidal Tract (corticospinal)
90% Crossed; 10% Uncrossed
Project to motor neurons and spinal interneurons
Origin in M1, premotor, postcentral
Premotor Cortex
The Cortex: Secondary Motor Areas
Supplementary Motor Area (SMA)
The Cortex: Association “Motor” Areas (take that vision chauvinists)
Pre-SMA
Views on hierarchical organization
1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory
Views on hierarchical organization
1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory
2. Flexibility: Contextualization of ActionExploiting degrees of freedom
Views on hierarchical organization
1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory
2. Flexibility: Contextualization of ActionExploiting degrees of freedom
3. Abstraction of controlGoal > Action > Movement
e.g., reaching for coffee cup
Views on hierarchical organization
1. Degree of sensory integrationSpinal mechanisms: Limited to somatosensoryCortex: Polysensory
2. Flexibility: Contextualization of ActionExploiting degrees of freedom
3. Abstraction of controlGoal > Action > Movement
e.g., reaching for coffee cup
4. Other ???
Motor Learning
Three 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 Learning
Three paradigms:
Force field learning
Visuomotor transformations
DEMO
Motor Learning
Three paradigms:
Force field learning
Visuomotor transformations
examples: displacements, rotations, inversions, reversals (mirror drawing), depth distortions
Motor Learning
Three paradigms:
Force field learning
Visuomotor transformations
Sequence learning
Serial Reaction Time Task
Press response key corresponding to stimulus position.
Stimuli follow sequence or are chosen at random.
Motor Learning
Three paradigmsForce field adaptationVisuomotor transformationsSequence learning
Does one term (motor learning) fit all?
How to determine similarities/differences?
Motor Learning
S&W’s (anti)definition: Adaptation vs. Skills
Adaptation: 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 results
sensory vs. symbolic?
rate of learning?
Acquisition:error type? rate of learning?
Generalizationlocal or general? transfer?
SRT is symmetric Force field is better right to left VMT 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 field
B2: 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 Learning
Three paradigmsForce field adaptationVisuomotor transformationsSequence learning
Neural systems: Do these tasks engage common regions?