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

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?