Principles of Neuroscience Lecture 14 Modulation of Movement

Question 0

Describe the structure of the basal ganglia

Answer 0

5 discrete regions:
Caudate
Putamen
Globus Pallidus
Sub-thalamic nuclei
Substantial nigra

Question 1

Which two regions in the brain are modulatory centres for movement?

Answer 1

Basal Ganglia

Cerebellum

Question 2

Describe the localisation of the basal ganglia

Answer 2

Caudate: runs along edge of lateral ventricles
Putamen: base of forebrain - telencephalon
Globus pallidus: next to putamen : external then internal
Sub thalamic nuclei: under thalamus
Substantial nigra: mesencephalon - midbrain

Question 3

What are the functions of the basal ganglia (3)

Answer 3

1. Initiation of movement
2. Optimisation of movement, evaluation
3. Selection of movements from a repertoire

Question 4

What are the inputs to the Caudate-Putamen?

Answer 4

1. Cerebral cortex

2. Substantial nigra pars compacta

Question 5

What are the two output pathways from the Caudate Putamen?

Answer 5

Direct

Indirect

Question 6

Describe the direct pathway

Answer 6

1. Caudate putamen actively inhibits Globus pallidus internal
2. GPi can no longer carry out its normal activity of inhibiting the thalamus
3. Thalamus is not inhibited, so it activates the motor cortex

Question 7

Describe the indirect pathway

Answer 7

1. C-P inhibits the Globus Pallidus external
2. GPe can no longer inhibit the sub - thalamic nuclei, because it has been inhibited
3. Sub thalamic nucleus is not inhibited, so it excites the GPi
4. The GPi is activated, so it can carry out it’s function of inhibiting the thalamus
5. The thalamus is inhibited, so it can’t activate the motor cortex

Question 8

What is the role of the direct pathway?

Answer 8

Selection and activation of the desired movements

Question 9

What is the role of the indirect pathway?

Answer 9

Inhibition of competing movements

Question 10

What are basal ganglia loops?

Answer 10

Such as those we see here. They talk to the cortex.

They aren’t just associated with motor function

Question 11

What are the two dopamine receptors in the Caudate-Putamen?

Where is the dopamine coming from?

Answer 11

D1: activates direct pathway
D2: inhibits the indirect pathway

Dopamine is coming from the substantial nigra pars compacta

Question 12

Describe the pathology of Parkinson’s disease?

Answer 12

The cells in the substantial nigra pars compacta die

Dopamine is no longer released onto the caudate-putamen

There is no longer activation of movement via the two pathways

Question 13

When is a tremor first seen in Parkinson’s?

Answer 13

When 80% of the cells in the substantial nigra are already dead

Question 14

How does the substantial nigra pars compacta activate movement? (Two ways)

Answer 14

1. Activate the direct pathway, which is activating movement

2. Inhibits the indirect pathway, which is itself inhibitory. Thus, movement is activated

Question 15

What is a treatment for Parkinson’s?

Answer 15

L-DOPA:
Saturate brain in dopamine
Only regions that need it respond to it
C-P now has dopamine, and movement is activated

Deep brain stimulation:
Electrical stimulation of the C-P and GP
This causes retrograde activation of the pathway
This stops the tremor

Question 16

Describe the pathology of Huntington’s disease

Answer 16

Cells in C-P and GP die
GP normally inhibits the thalamus
No inhibition mean there are spontaneous and jerky movements

Question 17

What is the striatum?

Answer 17

This is the caudate and the putamen

Question 18

Describe deep brain stimulation?

Answer 18

Stimulation of the sub thalamic nucleus

Retrograde activation of the pathway, stopping the tremor and activating movement

Question 19

Describe the functions of the Cerebellum (3)

Answer 19

1. Start and stopping of movements: coordination
2. Motor learning
3. Plan formation
4. Maintenance of muscle tone

Does not itself initiate movement

Question 20

Where is the cerebellum?

Answer 20

Hindbrain: metencephalon

Question 21

What are the inputs to the cerebellum?

Answer 21

Frontal cortex
Proprioception
Vestibular nuclei

Question 22

What are the outputs from the cerebellum?

Answer 22

Motor cortex

Question 23

What is ataxia?

Describe the symptoms seen in a clinical test

Answer 23

Ataxia: “can’t follow the path”. This is when movement is inefficient because the brain does not form a plan about where the limb should go.
Eg. Touch a spot, then touch you nose
The path is not direct
The patient does not have the feed forward information