Function of Cerebellum/Basal Ganglia

Question 1

Feedback vs Feedforward Controller

Answer 1

f

Question 2

role of the parietal cortex in matching joint position sense with visual coordinates for a reaching motion

Answer 2

Visual info advances from occipital cortex to parietal lobe, neurons encode info about location in space of visual stimuli. (“where pathway”) In parietal association cortex, where pathway and joint position sense info from somatosensory cortex are integrated into info that is fed to motor cortices in frontal lobe to guide movement of the limb to the target. (calculate difference between current and desired location of effector and convey this to motor output (premotor corticies in BA 6) to produce desired joint angles.
Network has an internal model of system, makes predictions.

Question 3

Describe how the cerebellum can adapt cortical networks to changes in the relationship between joint position sense and visual coordinates

Answer 3

When prisms are applied, predictions of system are no longer valid. System must be recalibrated. Cerebellar pathways connecting parietal and premotor corticies effect re-calibration. Cerebro-cerebellum’s mossy fibers arise from contralateral pontine gray, these are innervated by cortico-pontine fibers descending thru internal capsule. Parietal cortex contributes a lot of these cortico-pontine fibers, which then form synapses with ponto-cerebellar neurons. So, mossy fibers are a reflection of state of parietal cortical mapping b/t visual and proprioceptive signals.

Mossy fibers synapse on granule cells whose parallel fibers hit Purkinje cells, whose output to dentate nucleus is relayed to thalamus and then motor and premotor corticies.

Question 4

Describe the role that dopaminergic neurons in the VTA/SNc play in conveying reward prediction errors to the striatum

Answer 4

f

Question 5

Describe similarities between the role the ION plays in modifying cerebellar circuitry and the role that VTA/SNc neurons play in modifying corticostriatal circuitry

Answer 5

f

Question 6

Inf Olivary nucleus and climbing fibers

Answer 6

ION sends climbing fibers to Purkinje cells.
Simultaneous discharge of climbing fibers and parallels fibers leads to changes in synaptic strength of parallel-purkinje synapses.