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
http://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S1.mov
Split-belt
Choi and Bastian, 2007
Rapid modification of “ancient” CPG
Stance Phase
Grey: Fast leg Black: Slow leg
Context-specific adaptation
Choi and Bastian, 2007
Rapid modification of “ancient” CPG
Hybrid walking: One leg forward and one leg backward
http://www.nature.com/neuro/journal/v10/n8/extref/nn1930-S5.mov
Split-belt
Choi and Bastian, 2007
Descending Signals: Extrapyramidal Pathways
Integration of other sensory
signals with spinal mechanisms.
Subcortical Characters: The Cerebellum
Multisensory (and other) inputs
Descending and ascending output
Subcortical Characters: The Basal Ganglia
Components of the
Basal Ganglia
Striatum
Globus Pallidus
Subthalamic nucleus
Substantia nigra
Anatomical features:
Multisensory/associative input
Complex internal circuitry
Restricted output
Replication of circuitry
The Cortex: Primary Motor Cortex
Motor Cortex
Pyramidal Tract
(corticospinal)
90% Crossed;
10% Uncrossed
Project to motor neurons
and spinal interneurons
Origin in M1, premotor,
postcentral
Internal capsule
The Cortex: Secondary Motor Areas
Premotor Cortex
Supplementary Motor
Area (SMA)
The Cortex: Association “Motor” Areas
(take that vision chauvinists)
Pre-SMA
Views on hierarchical organization
1. Degree of sensory integration
Spinal mechanisms: Limited to somatosensory
Cortex: Polysensory
Views on hierarchical organization
1. Degree of sensory integration
Spinal mechanisms: Limited to somatosensory
Cortex: Polysensory
2. Flexibility: Contextualization of Action
Exploiting degrees of freedom
Views on hierarchical organization
1. Degree of sensory integration
Spinal mechanisms: Limited to somatosensory
Cortex: Polysensory
2. Flexibility: Contextualization of Action
Exploiting degrees of freedom
3. Abstraction of control
Goal > Action > Movement
e.g., reaching for coffee cup
Views on hierarchical organization
1. Degree of sensory integration
Spinal mechanisms: Limited to somatosensory
Cortex: Polysensory
2. Flexibility: Contextualization of Action
Exploiting degrees of freedom
3. Abstraction of control
Goal > 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
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 paradigms
Force field adaptation
Visuomotor transformations
Sequence 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?
Generalization
local 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?
Generalization
local 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 paradigms
Force field adaptation
Visuomotor transformations
Sequence learning
Neural systems: Do these tasks engage common regions?