Control of Movement

Question 1

Why is movement difficult to replicate electronically?

Answer 1

→ The brain predicts movement

Question 2

What are the basal ganglia?

Answer 2

→ A group of nuclei inside the brain

Question 3

What kind of a disease is Parkinsons?

Answer 3

→ basal ganglia degenerative disease

Question 4

What do the basal ganglia act as?

Answer 4

→ Relay stations

Question 5

What are the 3 different circuits in the brain?

Answer 5

→ Motor
→ Associative
→ Limbic

Question 6

How are the basal ganglia segregated?

Answer 6

→ Anatomically

Question 7

What is the main output of the basal ganglia?

Answer 7

→ inhibitory

Question 8

What are the 2 basal ganglia pathways?

Answer 8

→ One decreases output activity (increases movement)

→ One increases output activity (decreases movement)

Question 9

What sends inputs to the basal ganglia?

Answer 9

→ The striatum

Question 10

What is the indirect stop pathway?

Answer 10

→ Activates the inhibitory nucleus and makes movement less likely to happen

Question 11

What is the direct go pathway?

Answer 11

→ Inhibits the inhibitory pathway

Question 12

Where is dopamine produced?

Answer 12

→ In the substantia nigra

Question 13

What is the Alexander and Delong model?

Answer 13

→ Changes in firing rate (of the output nuclei) determine the degree of thalamic inhibition and the amount of movement possible

Question 14

What is bradykinesia?

Answer 14

→ A lack of movement

Question 15

What happens in Parkinsons?

Answer 15

→ Substantia nigra degenerates
→ Not enough dopamine
→ Inhibitory output of the basal ganglia turns up
→ Inhibits the thalamus and inhibits the motor cortex
→ rate of firing of the output nucleus goes up

Question 16

What is hemiballismus and what is it caused by?

Answer 16

→ A flinging movement of one side of the body

→ caused by a subthalamic nucleus stroke

Question 17

What role does the subthalamic nucleus have?

Answer 17

→ it is a key node in the stop pathway

Question 18

What happens if the subthalamic nucleus is removed?

Answer 18

→ excessive inhibition of the stop pathway or an inhibitory output nucleus
→ the Gpi/SNr is not stopping the thalamus
→ excessive movement

Question 19

What is a clinical issue with the Alexander and Delong model?

Answer 19

→ lesioning the thalamus does not cause prominent akinesia

→ lesioning the GPi does not cause dyskinesia

Question 20

What is the beta frequency?

Answer 20

→ 20-30 Hz

Question 21

What is the firing like in people with motor disorders?

Answer 21

→ the neurons have a bursty pattern

→ the rate of firing is not abnormal but the pattern of firing is

Question 22

in a normal situation what do brain electrodes pick up and what happens in Parkinsons?

Answer 22

→ lots of different frequencies firing

→ Everything becomes synchronised

Question 23

When does dopamine release occur?

Answer 23

→ At the beginning of movement

Question 24

People with Parkinsons still produce dopamine, why is this not enough for movement to occur?

Answer 24

→ There is a baseline level of dopamine release
→ additional dopamine release happens at the beginning of movement
→ people with Parkinsons have low baseline dopamine
→ When a stimulus occurs the additional dopamine released it not enough to pass the threshold for movement.

Question 25

How do you define moving?

Answer 25

→ Change from one stable sensory state to another stable sensory state

Question 26

What are the 3 things required for changing sensory states?

Answer 26

→ Turning down current sensory state
→ Accurate prediction of the new sensory state
→ Stabilising the new sensory state

Question 27

What is involved in stabilising sensory states?

Answer 27

→ Beta power

Question 28

What is beta power like when sitting still and why?

Answer 28

→ It is high

→ stops you having other unneeded movements such as jumping

Question 29

If you want to move what happens to beta power?

Answer 29

→ It is turned down which allows you to change state

Question 30

What allows prediction of movement in the brain?

Answer 30

→ The brain builds internal models of the world

Question 31

What is the forward model?

Answer 31

→ Brain sends a copy of the movement to the cerebellum to check if the movement is correct

Question 32

What does the forward model do?

Answer 32

→ Comparing what happened with what was expected to happen

Question 33

What happens when there is damage to the cerebellum?

Answer 33

→ movement becomes steady and uncoordinated because the comparison can’t happen
→ the brain is unprepared for obstacles

Question 34

What is abnormal in Parkinsons?

Answer 34

→ initiation
→ Scaling
→ and persistence of movement