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Neuro > Control of Movement > Flashcards

Control of Movement Flashcards

1
Q

The Basal Ganglia

A

A group of nuclei which are central to control of movement

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2
Q

Movement disorders

A

A diverse array of neurological illness that results in disorderd control of movement

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3
Q

Efference copy

A

A prediction of expected movement outcome which is generated at the same time as the movement signal and which is compared with the actual movement outcome.

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4
Q

How is the movement control processed?

A

It is processed at different levels

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5
Q

Describe the basal ganglia as a multiple relay system

A

It takes a massive input from multiple cortical and brainstem regions, and outputs to selected parts of the same areas for focussed function.

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6
Q

What is just as important as motor functions of the basal ganglia?

A

Non-motor processing

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7
Q

What are the circuits of the multiple relay system of the basal ganglia?

A
  • Motor circuit
  • Associative circuit
  • Limbic circuit
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8
Q

How is the basal ganglia divided anatomically?

A

The basal ganglia is segregated anatomically and between the circuits but also further subdivided anatomically so the circuit will project to different basal ganglia nuclei that are all connected.

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9
Q

What is the main output from the basal ganglia?

A

Inhibitory - so less movement

Increase the activity of the basal ganglia then there is less movement.

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10
Q

Why is the function of the basal ganglia important?

A

It is important to link the emotional and cognitive function as sometimes the importance of not doing something.

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11
Q

What are the two pathways in the basal ganglia?

A
  • Direct go pathway

- Indirect stop pathway

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12
Q

What neurotransmitter affects the two pathways of the basal ganglia?

A

Dopamine produced by the substantia nigra

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13
Q

Direct Go Pathway

A

Inhibiting the inhibitory output nucleus hence promoting movement - decreased output activity from basal ganglia so increased movement

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14
Q

Indirect Stop Pathway

A

Excitatory onto inhibitory nucleus hence making less movement happen = increased output activity from basal ganglia so decreased movement.

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15
Q

What neurons input into the basal ganglia?

A

The striatum - medium spiny neurons

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16
Q

Substantia nigra

A

Part of the brain producing dopamine

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17
Q

Which part of the brain is damaged in Parkinson’s Disease?

A

Substantia nigra

18
Q

Describe the motor circuit

A
  • Motor cortex releases signals to the putamen which if increasing movement will cause the release of dopamine from the substantia nigra and then distributes to basal ganglia and other regions including thalamus
19
Q

The rate (Alexander and Delong) model

A
  • Changes in firing rate (of output nuclei) determine the rate of thalamic inhibition and therefore amount of movement possible
  • If increased firing rate, then the basal ganglia goes up there is inhibition of movement.
20
Q

Parkinson’s Disease

A
  • Long term degenerative disorder of the CNS that mainly affects the motor system.
  • Clinically dominated by a lack of movement = bradykinesia
  • The substania nigra degenerates so not enough dopamine.
  • Inhibitory output of the basal ganglia so inhibits motor cotex stopping movement
21
Q

Bradykinesia

A

Decreased bodily movement

22
Q

Hemiballismus

A
  • Involuntary flinging movement to one side of the body due to subthalamic nucleus stroke
  • Excessive inhibition of the inhibitory output nucleus causing hyperkinesia as the thalamus and motor cortex are not stopped
23
Q

Hyperkinesia

A

Increase in muscular activity that results in excessive normal movements

24
Q

Function of the sub thalamic nucleus

A

Key regulator in preventing movement - if it doesn’t exist then there is no inhibition of thalamus and motor cortex

25
Q

Clinical problems with the rate model

A
  • Patients with movement disorders have been treated with lesions in parts of the brain to identify treatment
  • Results are unexpected as lesioning thalamus does not promote akinesia
  • lesioning the GPi does not cause dyskinesia
26
Q

What have animal models with Parkinson’s shown about the function of the basal ganglia?

A

It is not the level of BG output but the pattern that is important.

27
Q

What did deep brain stimulation surgery show about neurons in Parkinson’s disease?

A

Showed that there is a particular frequency at which the nerve cells fire around 20-30 hz (beta frequency). In PD, the beta frequency is high reducing movement rather than increased firing to the region.

28
Q

How is neuron frequency recorded in humans?

A
  • Usually carried out in disorder patients to see how the frequency differs
  • In a normal situation, there are a lot of different frequencies of firing in different nerve cell populations.
  • Differential frequency firing allows the carrying of lots of information in the multiple patterns of firing.
  • In Parkinson’s everything is synchronised and reduces the information processing and transfer.
29
Q

What evidence is there that beta activity is high in individuals with Parkinson’s?

A
  • Levodopa medication suppresses beta activity and reduces the synchronised firing - ON frequency falls when on medication. This results in greater movement when the beta activity is suppressed.
  • Deep brain stimulation surgery can also suppress beta frequencies shown improve movement
  • Direct stimulation of the STN at beta band frequencies worsened Parkinson’s
  • Dopamine treatment will improve movement as in PD, there is a reduction of dopamine so no movement.
30
Q

What is moving?

A

The change from one (stable) sensory state to another (stable) sensory state.

31
Q

Steps for moving state changes

A
  1. Turn down beta power
  2. The basal ganglia will get ready to destabilise the state to allows for new sensory state
  3. Stabilise the beta power will increase again
32
Q

How does the brain work from Bayes to Free energy

A
  • The brain has a system that allows us to build internal models of the world. Therefore, we know how the world is meant to work and how the body is meant to interact with the world
  • Needs to be a mechanism that turn up/down the particular state in order to allow the maintainence of a state or transition into a new state
  • There are two possibilities: to stay in the current state or move
33
Q

What does the brain do when the body does not move?

A

Turn up the strength of the current sensory state keeping a static essentially high beta activity that prevents movement from happening

34
Q

What does the brain do when the body needs to move?

A

Beta activity is reduced which will turn down the strength of the current sensory state and allows a new prediction to emerge

35
Q

What is the systemic approach to motor control?

A

All of the different areas that feed information in order for motor control

36
Q

Sensory neuropathy

A

Loss of joint position sense and sensation sense - no damage to the brain but loss of sensory feedback coming in.

37
Q

How does the brain check that the input received is correct?

A

Sends a signal to the cerebellum that receives sensation information from the body and makes sure it is the expected response.

38
Q

What happens if there is damage to the cerebellum?

A

Results in the person being unsteady and uncoordinated, the comparison cannot take place so the brain isn’t able to adapt to errors that occur in movement

39
Q

Cerebrellar disorders

A

Person cannot learn to walk normally and adapt to new situations

40
Q

Why do people with parkinsons have trouble going through doors?

A

The idea from switching from one sensory state to another means they are stuck in a synchonous state due to high beta activity that prevents from changing state

41
Q

Tourette’s Syndrome

A

Chronically low beta activity so the sensory state is unstable meaning that movement is present in an uncensored way

Neuro (20 decks)

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