Motor Systems Flashcards
What are the 4 subsystems and where are they in the brain
Lower motor neurons in spinal cord and brainstem
Upper in cortex and brainstem
Cerebellum
Basal ganglia
What is the role of the primary motor cortex
Cortical source of movement signals sent to brainstem and spinal cord
What is the role of the basal ganglia
Initiation and inhibition of movements and reward based learning
What is the role of the superior colliculus
Control of eye movements
What is the role of the pre motor cortex
Motor planning and awareness of motor intentions
What is the role of the supplementary motor cortex
Production of internally generated sequences of movements
What is the role of the cerebellum
Coordination, error correction, and the learning of fine skilled movements
The premotor cortex is ______ to the primary cortex
Rostral
The cerebellum is ______ and _______ to the basal ganglia
Posterior and inferior
Is conscious control (inhibition) of a flexion reflex possible
Yes, if the intention not to respond was prepared in advance so the signal could be sent to the reflex pathway before the stimulus occurred, to inhibit it when it did occur.
What is an inverse model used for
Used to create motor plans.
Current position and desired position create a motor command.
What are forward models used for
Used to evaluate motor plans and action.
Current position and motor commands create a predicted position.
What is a feed forward controller used for
Direct motor command sent quickly to muscle
What is a feedback controller used for
Adjustment of movement based on errors evaluated by comparing the actual state to the desired state. Slower, but more accurate.
What does each hemisphere of the cortex control
The contralateral side of the body
What is a tuning curve
A curve to summarize response rates as a function of direction of movement
What are the 4 intraparietal sulcus areas (IP)
Lateral IP
Ventral IP
Medial IP
Anterior IP
What does the Lateral IP represent
Space for eye movements
What does the Ventral IP represent
Space for facial movements
What does the Medial IP represent
Space for arm movements
What does the Anterior IP represent
Space for hand movements
What is the direct pathway for motor initiation
Motor cortex –> striatum –> globus pallidus pars interna (GPi)/ substantia nigra pars reticulata (SNr) –> thalamus –> back to cortex
What is the indirect pathway for motor initiation
Motor cortex –> striatum –> globus pallidus pars externa (GPe) –> subthalamic nucleus (STN) –> GPi/ SNr –> thalamus –> back to cortex
This pathway inhibits additional actions
How does reinforced learning work
Unexpected rewards generate dopamine signals from the substantia nigra pars compacta (SNc) which excites the direct pathway and inhibits the indirect pathway.
What models does the cerebellum use for online error correction and motor learning
The cerebellum uses a forward model to predict results of motor commands, and feedback control
Local circuits in the spinal cord… (3)
Can control complex movements
Can respond to environmental changes
Do not require higher-level input
What do lower motor neurons directly synapse to
Lower motor neurons directly synapse on muscle fibers
What causes muscle fibers to contract
The release of neurotransmitters
What do muscle spindles do
Muscle spindles detect changes in muscle length and send the changes back to the spinal cord via the dorsal root ganglia
What does the supplementary motor area do
The supplementary motor area generates movements in the absence of explicit sensory cues (well-learned movements)
What is the role of the parietal cortex
It is crucial for sensory-motor coordination
What is the basal ganglia composed of
3 nuclei: caudate & putamen (striatum) and globus pallidus
Plus: subthalamic nucleus and substantia nigra pars compacta
