Action Flashcards
inverse models
Current position and desired position –> Motor commands.
- Used to create motor plans
forward models
Current position and Motor commands –> predicted position. Used to evaluate motor plans and/or action.
feedforward control
Motor command sent to muscle
Faster, but less accurate
feedback control
Motor command sent to muscle
Actual state compared to desired state, adjustments made based on errors
Slower, but more accurate
Premotor cortex role
- Involved in selecting goals and planning actions at a conceptual level, occurs before voluntary movement
- Particularly when plans are driven by external stimuli
Supplementary motor cortex (SMA) role
- Involved in selecting goals and planning actions at a conceptual level
- Particularly when plans involve internally generated sequences of actions (e.g. tying shoelaces)
Motor cortex/superior colliculus
- Motor cortex represents directional movements of body parts, not specific muscle actions
- Signals from motor cortex travel directly to lower motor and circuit neurons in brainstem and spinal cord
Basal ganglia role
- Help to select, initiate and inhibit movements through cortico-basal ganilia-thalamocortical loops
- Critical to dopamine-based reinforment learning
- Participate in motor, cognitive, and emotional control
Action initiation
Direct pathway
- Motor cortex excites striatum
- Striatum inhibits GP i/SNr
- GP i/SNr disinhibits thalamus
- Thalamus excites cortex
Population vector
- Accurately represents actual movement direction
- Treats firing of each neuron as a vector, then adds together
Direct pathway
- Motor cortex
- Striatum
- Globus pallidus pars interna/Sustantia nigra pars reticulata
- Thalamus
- Motor cortex
Indirectly pathway
- Cortex
- Striatum
- Globus pallidus pars externa
- Subthalamic nucleus
- Globus pallidus pars interna/Sustantia nigra pars reticulata
- Thalamus
- Cortex
Action inhibition
Indirect pathway
- Motor cortex excites striatum
- Striatum inhibits GPe
- GPe disinhibits STN
- STN excites GP i/SNr
- GP i/SNr reinhibits thalamus
Reinforcement learning
- Unexpected rewards
generate dopamine signals
from the substantia nigra
pars compacta (SNc) - This excites the direct
pathway (via D 1 receptors)
and inhibits the indirect
pathway (via D 2 receptors) - This allows modification of
behavior based on reward
Cerebellum role
- Uses forward model to
predict results of motor
commands - Uses differences between
actual results and
predicted results for:
●Online error correction
● Motor learning - Feedback control
