L7 - Cerebellum and Motor Learning

Question 1

What percentage of neurons in the brain are found in the cerebellum?

Answer 1

Over 50%

Question 2

What inputs information into the cerebellum?

Answer 2

Mossy fibres and climbing fibres

Question 3

Where do the inputs into the cerebellum feed into?

Answer 3

Purkinje cells

Question 4

How many mossy fibres are needed to activate one purkinje fibre?

Answer 4

200

Question 5

How many climbing fibres are needed to activate one purk`inje fibre?

Answer 5

1

Question 6

The output from the cerebello cortex projects to what?

Answer 6

Deep cerebellar nuclei.

Question 7

If someone had a lesion to their cerebellum, what would they suffer from?

Answer 7

Inability to make accurate movements.

Question 8

What is ataxia?

Answer 8

A loss of co-ordination and skill

Question 9

What is hypermetria?

Answer 9

An overshoot of fine/precision movement. Gross movement is fine, but the accuracy of the finer movement lacks - means putting finger to nose is more difficult.

Question 10

What is intention tremor?

Answer 10

A tremor that is induced from movements, or when focussing on a certain task.

Question 11

What might happen should cerebellum damage occur?

Answer 11

• Ataxia
• Hypermetria
• Intention tremor
• Nystagmus, balance, speech deficits
• Cerebellar affective disorder: executive, emotional and personality issues.

Question 12

Where does the cerebellar nuclei project/output to?

Answer 12

• Motor and pre-motor cortex

- Spinal cord

Question 13

What is the gain?

Answer 13

How much input leads to how much output - calibration process between sensory and motor systems.

Question 14

What happens when there is an error, for example, retinal slip, in the VOR?

Answer 14

An error signal transmits through climbing fibres to the Purkinje cells, leading to depression of the synaptic connections. This means that the cell fires less the next time it happens, meaning a stronger response next time (as the Purkinje cells have an inhibitory effect)

Question 15

How do climbing fibres initiate LTD?

Answer 15

They fire a teaching signal which causes calcium ions to enter.

Question 16

Explain the role of calcium ions in LTD.

Answer 16

Calcium ions internalise AMPA receptors and puts them into stores/recycles them.

Question 17

Why is LTD an associative mechanism?

Answer 17

Parallel fibres have to be active/firing at the same time, or during a specific time frame, that the climbing fibres’ teaching signals are active.

Question 18

Spikelets give us an indication of what occurring?

Answer 18

Error in our system, in terms of an event occurring that we did not expect.

Question 19

What do climbing fibres cause

Answer 19

Simple Spikes and complex spikes.

Question 20

What do simple spikes represent?

Answer 20

Signals being sent to Purkinje cells from mossy fibres - indicating that no error has occurred.

Question 21

What do complex spikes represent?

Answer 21

Signals being sent to Purkinje cells from climbing fibres- indicating error in the system.

Question 22

Would adults or children be faster at visuomotor adaptation (prism glasses) and why?

Answer 22

Adults, as their cerebellum is more developed.

Question 23

What is the main role of the cerebellum?

Answer 23

Sensory motor integration and prediction.

Question 24

Where do the climbing fibres and their teaching signals originate from?

Answer 24

Inferior olive

Question 25

What is the large output from the cerebellum to the prefrontal lobe for?

Answer 25

• Potential roles in cognitive tasks such as planning, attention and language.
• Links to autism, affective disorders and dyslexia.

Question 26

What is the Marr-Albus model of learning?

Answer 26

Concerns changing the strength of connections between parallel fibres and purkinje cells through long term depression.