lec 22 - central motor system

Organization of motor cortex

topographic map, rough somatotopic organization, action zone organization

Brain areas involved in action planning

supplementary and premotor cortex, premotor cortex neurons active well before movement execution

Premotor area (PMA) cells (respond to, prefer __ movements, contribute to, activate when)

respond to instruction until movement, prefer particular movements, contribute to movement planning, activate well before movements

Cells in primary motor cortex (M1) respond best to

particular direction of movement, and are broadly tuned so they respond over a range of movement directions

What is population vector

mean response from many M1 cells, and it correlates well with movement direction

How does a population of neuron activity look at the start of movement population compared to just before the movement

varies less from trial to trial and converges to one point in the state space

Plasticity of motor cortex

more cells you have for an action, the finer the control you have

Changes in motor cortex after peripheral lesion

organization of neurons may change and representations of movements in motor cortex can change, can occur from learning experiences or injury

What are lateral pathways (pathway through __, controls, terminates in, list tracks)

pathway through the spinal cord, controls fine movements of arms and fingers, terminates in ventral horns where lower motor neurons and interneurons are, corticospinal and rubrospinal track

Corticospinal track (which pathway, where to where)

major track in lateral pathway, motor cortex to spinal cord

Rubrospinal track (which pathway, where to where)

minor track in lateral pathway, red nucleus to spinal cord

What are ventromedial pathways (pathway from _ through _, controls, list tracks)

pathway from brainstem through spinal cord, controls proximal and axial muscles, vestibulospinal track, tectospinal track, pontine reticulospinal track, medullary reticulospinal track

What pathway used to maintain balance and body posture

ventromedial pathway which is under control of motor cortex

Vestibulospinal track (which pathway, function, where to where)

in ventromedial pathway, keeps head and eyes stable, from vestibular nucleus to spinal cord

Tectospinal track (which pathway, function, where to where)

in ventromedial pathway, orients head and eyes to stimuli, from superior colliculus to spinal cord

Pontine reticulospinal track (which pathway, function, where to where)

in ventromedial pathway, keeps upright posture, from pontine reticular formation to spinal cord

Medullary reticulospinal track (which pathway, function, where to where)

in ventromedial pathway, counters pontine tract, from medullary reticular formation to spinal cord

What pathway facilitates wanted action

direct pathway through basal ganglia and excite thalamus

What pathway facilitates unwanted actions

indirect pathway through basal ganglia to inhibit thalamus

What does the cerebellum do (integrates to give, general pathway)

integrates motor commands, current states, and errors to get automatic motor command or sensory prediction, cortex to pons to cerebellar cortex to deep cerebellar nuclei to thalamus to cortex

Forward model in cerebellum (_ from _ cortex through __ fibers to get)

Copy of motor response from frontal cortex through mossy fibers to get predicted sensory consequence

Inverse model in cerebellum (_ from _ cortex through __ fibers to get)

state of world/body from parietal cortex through mossy fibers to get automatic action command

Error pathway in cerebellum (_ from _ through __ fibers)

errors from inferior olive through climbing fibers