cerebellum and basal ganglia function

Question 1

control theory

Answer 1

a branch of engineering and mathematics that deals with dynamical systems (dynamical systems are
mathematical models of the behavior of a point over time.) a branch of engineering and mathematics that deals with dynamical systems (dynamical systems are
mathematical models of the behavior of a point over time.)

Question 2

1. Understand the difference between a feedback and feedforward controller, and the value of prediction in motor control

Answer 2

In the context of a thermostat: 1. feedback regulator: heater turns on when room drops below threshold, and cooler turns on when temp exceeds a threshold. Tends to be slow and attempts to speed it up cause oscillations (too hot to too cold). 2. Feedforward regulator: Uses sensory data to predict future states and preemptively counteracts temp change. (ie sensing variables such as how many windows are open, outside temp, etc). will acheive target value and stay there

Question 3

Adaptive feedforward control

Answer 3

Uses sensory data to predict future states, but also generates a targeting error when things change so that next time it will be more effective.

Question 4

What kind of control is the cerebellum

Answer 4

adaptive feedforward controller

Question 5

How does a prism affecting reaching movement in a normal person and in someone with cerebellar damage

Answer 5

Predictions of system are no longer valid. Normal: CNS is able to adapt to the change in vision. Damaged: Can not adapt to the prism and will constantly point beyond the target.

Question 6

What areas of brain are involved in estimating position of limb in space

Answer 6

Joint position is sent to primary somatosensory cortex in post central gyrus, and visual info is sent to occipital cortex

Question 7

describe components of the “what” and “where” pathways

Answer 7

visual information goes to occipital cortex then can take two pathways. 1. The what pathway: info from occipital lobe is sent via ventral visual stream to inferior temporal lobe where object form is encoded. 2. The where pathway: info from occipital lobe is sent dorsally into parietal lobe where the location in space of visual stimuli is encoded

Question 8

Role of parietal association cortex

Answer 8

In parietal association cortex, btw the “where” pathway and the joint position info from somatosensory cortex, the brain integrates visual information about the target (and limb position) and somatosensory information about the limb position, and this integrated information is fed to the premotor corticies in the frontal lobe to guide movement of the limb to the target.

Question 9

Parietal association cortex internal model

Answer 9

This network contains an internal model of the system, which specifies certain predictions: for a given visual coordinate, the system predicts that certain joint angles
will achieve that locationThis network contains an internal model of the system, which specifies certain predictions: for a given visual coordinate, the system predicts that certain joint angles
will achieve that location

Question 10

Describe cerebellar pathway connecting parietal and pre-motor cortices

Answer 10

parietal cortex > cortico-pontine fibers > synapse on ponto-cerebellar neurons (mossy fibers) > cross midline > synapse on contralateral cerebellar granule cells > parallel fibers synapse on purkinje cells > output to dentate nucleus > thalamus > motor and pre motor cortices

Question 11

4. Describe how the inferior olivary nucleus might contribute to joint position/ visual adaptation

Answer 11

Inferior olivary nucleus sends climbing fibers to purkinje cells and stimulation of these climbing fibers simultaneously with parallel fibers leads to changes in synaptic strengths of parallel-purkinje synapses, reconfiguring the network

Question 12

What drives inferior olivary activity

Answer 12

GABAergic neurons from deep cerebellar nuclei

Question 13

What kind of info does the inferior olivary nucleus receive

Answer 13

proprioceptive and visual feedback

Question 14

How does the inferior olivary nucleus act as a comparator

Answer 14

It compares the expected state with observed state. If the proprioceptive and visual feedback are exactly
what the current parietal network would predict, then the reflection of the parietal network conveyed to the ION cancel out the proprioceptive and visual feedback, and no change in ION activity would result. If the feedback are different from expected, the ION will produce an error signal proportional to the magnitude of difference btw observed and expected states. It compares the expected state with observed state. If the proprioceptive and visual feedback are exactly
what the current parietal network would predict, then the reflection of the parietal network conveyed to the ION cancel out the proprioceptive and visual feedback, and no change in ION activity would result. If the feedback are different from expected, the ION will produce an error signal proportional to the magnitude of difference btw observed and expected states.

Question 15

How is the error signal from inferior olivary nucleus conveyed

Answer 15

Error signal is carried by climbing fibers to the cerebellar cortex, where it initiates complex spikes in purkinje cells. The parallel fiber synapses on purkije cells that were active simultaneously with the climbing fiber-induced complex spike undergo a change in synaptic plasticity, termed Long Term Depression, leading to decrease in parallel fibers efficacy of firing the purkinje cell

Question 16

Which cells in the cerebellar cortex and basal ganglia serve as pattern recognizers

Answer 16

cerebellar cortex: purkinje cels. Basal ganglia: medium spiny cells of striatum

Question 17

5. Understand the role that dopaminergic neurons in the Ventral Tegmental Area/substantia nigra play in conveying reward prediction errors to the striatum

Answer 17

When an unexpected reward is achieved (receiving ice tea after pressing a button), there is a spike in number of action potentials produced by dopaminergic neurons in SN and VTA. Eventually, the spike of dopaminergic neural activity will occr just when the button is seen, then eventually dopamine release will stop completely

Question 18

describe the histochemical stain for Mu-opioid receptors of the striatum

Answer 18

Has patches that stain densely and a matrix that does not stain. Both the patch and matrix have medium spiny GABAergic neurons, but the matrix contains the neurons who project via the direct and indirect pathways.

Question 19

Where do neurons in the “patch” of the striatum project

Answer 19

Directly to the substantia nigra/ ventral tegmental area dopaminergic neurons. They convey the current predictions about rewards

Question 20

How is the substantia nigra/ ventral tegmental area a comparator

Answer 20

It detects mismatch btw observed and expected rewards. An unpredicted reward will strongly activated these neurons, and the dopamine released into the striatum will alter the activity and the plasticity of corticostriatal networks, such that networks that correctly predicted the error will be reinforced,
and those that do not correctly predict the error will be diminished.

Question 21

6. 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 21

Just as the ION acted as a comparator that was activated by a mismatch between observed and expected sensory feedback, the SNc/VTA acts as a comparator activated by a mismatch between observed and expected rewards.

Question 22

Compare basal ganglia and cerebellum: source of error signal, return projection

Answer 22

Error signal: For the basal ganglia, the input from dopaminergic neurons provides the error signal; for the cerebellum it arises from neurons in the ION. Return projection: In the basal ganglia, return projection
comes to DA neurons from small groups of striatal medium spiny neurons in the patches or striosomes. In the cerebellum, this return projection comes to the ION neurons directly from the deep cerebellar nuclei or indirectly via the red nucleus