Function of Cerebellum-Basal Ganglia 2

Question 1

How do dopaminergic neurons recognize reward prediction errors:

Answer 1

1. striosome conveys current predictions about – reflect present state of cortico-striatal network to these neurons
2. Additional inputs to the SNc/VTA convey info about actual reward experience.
3. ACTS AS A COMPARATOR – activated by mismatch between observed and expected rewards

Question 2

The mu-opioid receptor is located:

Answer 2

throughout the striatum (of basal ganglia) except for in certain patches.

Question 3

patches where the mu-opiod receptors are missing are the

Answer 3

striosome

with medium spiny GABAergic neurons who project through direct pathways to the SNc/VTA dopaminergic neurons.

Question 4

how do dopaminergic neurons in the VTA/SNc acts as a comparator

Answer 4

1. unexpected reward will strongly activate neurons
2. dopamine releases into striatum to alter the activity and PLASTICITY of cortico-striatal networks.
3. Networks that correctly predicted the error will be reinforced and those that do not correctly predict the error will be diminished

Question 5

Cerebellar pathways connecting parietal and premotor corticies effect a re-calibration so that if the visual coordinations (like adding a prism) and a given set of joint angles are different, ____

Answer 5

the brain can adapt for this. ONLY PERIOD OF ADAPTATION DEPENDS ON CEREBELLUM!!!

Question 6

Cerebro-cerebellum’s mossy fibers arise from___

Answer 6

contralateral pontine grey

Question 7

Mossy fibers are innervated by

Answer 7

cortico-pontine fibers descending through internal capsule.

Question 8

_____ contributes these cortico-pontine fibers that synapse on ponto-cerebellar neurons.

Answer 8

Parietal cortex

Question 9

Mossy fiber input =

Answer 9

reflection of present state of parietal cortical mapping between visual + proprioceptive signals.

Question 10

mossy fibers form synapses on

Answer 10

granule cells

Question 11

granule cells form synapses on

Answer 11

purkinje cells

Question 12

purkinje cells output is to the

Answer 12

dentate nucleus–>
thalamus–>
motor and premotor cortex

Question 13

ION sends climbing fibers to

Answer 13

purkinje cells

Question 14

The simultaneous discharge of olivary climbing fibers and parallel fibers leads to

Answer 14

changes in synaptic strengths of parallel-purkinje synapses, which can reconfigure the network.

Question 15

Comparator

Answer 15

compares the expected state with the observed state

Question 16

Expected state:

Answer 16

conveyed by deep cerebellar nuclei as a reflection of parietal network

Question 17

Observed state

Answer 17

conveyed by visual and proprioceptive feedback

Question 18

The ION acts as a

Answer 18

comparator

Question 19

The ION receives feedback about

Answer 19

proprioception and visual feedback

Question 20

The ION has

_____ neurons

Answer 20

GABAergic neurons

Question 21

The major input to the ION

Answer 21

from deep cerebellar nuclei

1. multiple sensory modalities which are different based on the subregion of ION they go to
2. These subregions project to different functional zones of the cerebellum

Question 22

ION, if the feedback is different than the expected:

Answer 22

the error signal is generated by ION

Question 23

Error signal is conveyed by

Answer 23

climbing fibers to cerebellar cortex.

Question 24

In the cerebellar cortex, the error signal:

Answer 24

initiates complex spikes in purkinje cells

The parallel fiber synapses on purkinje cells

Question 25

Long Term Depression:

Answer 25

1. change in synaptic plasticity of these parallel fiber synapses on purkinje cells.
2. Inverted form of longterm potentiation.
3. Simultaneous activity of the parallel fiber and climbing fiber leads to a decreases in parallel fiber’s efficacy in firing of Purkinje cell.

Question 26

Result of ION error signal

Answer 26

change in ensemble of active purkinje cells so that the ensemble that was active in erroneous movement has been deactivated and new ensemble conveys a revised reflection of parietal cortex’s mapping of visual and proprioceptive coordinates to the motor cortices.