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

Question 35

What is the relationship between firing rate of basal ganglia and thalamic inhibition?

Answer 35

inversely correlated

Question 36

What does removal of STN do to the thalamus?

Answer 36

knocks out excitatory pathway of BG and thus thalamus increases in firing so more movement​

Question 37

What does beta suppression lead to in Parkison's?

Answer 37

correlates with reduction in Parkinson’s symptoms​

Question 38

In Parkinson's what about the firing determines disorders?

Answer 38

a particular rhythm abnormality appears to disturb control of movement, resulting in slow initiation and poor scaling (size, vigour) of movement

Question 39

What does high beta power mean in Parkinson's?

Answer 39

→High beta means that the current sensory state is excessively stable, therefore can’t initiate or stabilise new movement →Actual movements in Parkinson’s disease appear normal

Question 40

What does pathologically low beta result in?

Answer 40

→the current sensory state is unstable so that new, unwanted patterns of movement can arise and come out without will

Question 41

What is the treatment for many movement disorders?

Answer 41

→dopamine receptor antagonists which increase beta activity.​

Question 42

What is cerebella tremor?

Answer 42

→Possibly a problem with inappropriate response to sensory feedback that comes into the cerebellum​ →Things to do with corrective feedback- over correction.

Question 43

What is chorea and dystonia?

Answer 43

→arise from other motor control problems →core control of movement seems normal with “noise” added