Plasticity and Simple Motor Learning

Question 1

What does delay eye blink conditioning involve?

Answer 1

pairing a conditioned stimulus with an unconditioned stimulus which naturally causes an unconditioned response

Question 2

Describe eye blink conditioning before and after training

Answer 2

• before - the US causes the UR and the CS causes no response
• after - the CS causes the CR before the US is delivered

Question 3

What does eye blink conditioning involve?

Answer 3

repeatedly pairing the CS with the US and over time, the subject learns to associate the two stimuli

Question 4

What are the 3 key features of delay eye blink conditioning?

Answer 4

• time (CS is presented first and remains on until the US is presented)
• learning the association
• role of the cerebellum

Question 5

What are the 3 phases of delay eye blink conditioning?

Answer 5

1. acquisition – subject learns to associate a CS with a US; over time, the CS alone evokes a CR (anticipatory eyeblink before the US is presented)
2. extinction – CS is presented without the US; over time, the subject learns that the CS is no longer predictive of the US and the CR decreases in magnitude and frequency, which represents the subject’s unlearning or inhibition of the previously learned association (eventually no blinking is seen in response to CS as the association is weakened/suppressed)
3. reacquisition – CS is once again paired with US and the subject begins to relearn the association between the two; typically happens more quickly than the initial acquisition since the subject has a memory of the previous learning

Question 6

What does the rapid relearning in reacquisition indicate?

Answer 6

the initial association wasn’t entirely erased but was inhibited or suppressed during extinction

Question 7

What cells does the cerebellar cortex contain?

Answer 7

Purkinje, granule and stellate cells

Question 8

What are Purkinje cells?

Answer 8

inhibitory neurons with their cell bodies in the cerebellar cortex

Question 9

What does each Purkinje cell receive?

Answer 9

monosynaptic excitatory input from a single climbing fibre and 100,000 granule cells via parallel fibres

Question 10

What does each granule cell receive?

Answer 10

excitatory input from ~4 mossy fibres

Question 11

What does climbing fibre stimulation evoke?

Answer 11

complex spikes in Purkinje cells which help with motor learning and correcting errors during movement

Question 12

What does mossy fibre stimulation evoke?

Answer 12

simple spikes which help with ongoing motor control and fine-tuning

Question 13

What is the role of the cerebellum in delayed eye blink conditioning?

Answer 13

it integrates sensory information from the CS and US, leading to the CR after training

Question 14

What does LTD do at the granule-Purkinje synapse?

Answer 14

weaken the inhibition on the deep cerebellar nuclei, which facilitates the condition of the CR

Question 15

When does LTD occur at the granule-Purkinje synapse?

Answer 15

when the granule cells and climbing fibres fire together

Question 16

When does LTP occur at the granule-Purkinje synapse?

Answer 16

when granule cells fire alone without climbing fire activity (deep cerebellar nuclei inhibit climbing fibres)

Question 17

What is the Marr-Albus hypothesis?

Answer 17

a computational model that proposes that the cerebellum controls movements entirely by itself

Question 18

What is Kamin blocking?

Answer 18

failure to learn an association between a new stimulus and a US when the new stimulus is presented alongside a CS that already predicts the US

Question 19

What happens when the CS is presented without a US without deep cerebellar nuclei control?

Answer 19

granule cell activity coincides with climbing fibre activity, leading to LTD at the granule-Purkinje synapse, which weakens Purkinje cell inhibition on the deep cerebellar nuclei which prevents extinction i.e. CR persists

Question 20

What happens when the CS is presented without a US with deep cerebellar nuclei control?

Answer 20

climbing fibres are inhibited which allows granule cells to induce LTP at the granule-Purkinje synapse, leading to increased Purkinje cell inhibition on the deep cerebellar nuclei which reduces the CR i.e. extinction persists

Question 21

What is prediction error?

Answer 21

discrepancy between what is expected and what actually happens

Question 22

What does the Rescorla-Wagner model explain?

Answer 22

how the strength of associations between a CS and US change over time through learning

Question 23

What does the Rescorla-Wagner model assume?

Answer 23

there is a limit to the strength of the association; initially the association is weak/non-existent, but with repeated pairings, the association grows until it reaches a maximum strength (asymptote)

Question 24

When will learning occur with delay eye blink conditioning?

Answer 24

when the outcome (US) differs from what is expected

Question 25

What are limitations of the Rescorla-Wagner model?

Answer 25

• does not account for latent inhibition; when a CS is presented without a US for a while before conditioning, it becomes harder to learn the CS-US association
• does not handle contextual effects well, where the environment plays a role in conditioning
• assumes a linear relationship between learning and prediction error

Question 26

How do climbing fibres encode positive and negative prediction errors?

Answer 26

• before learning, climbing fibres are relatively inactive because there is no expected outcome
• during acquisition, they signal a positive prediction error (unexpected US) and Purkinje cells adjust their firing through LTD, allowing the CR to develop
• during extinction, when the CS is presented without the US, they encode a negative prediction error, leading to a weakening of the learned response
• after training, the CS pauses Purkinje cell activity because LTD weakens the excitatory input from granule cells, allowing the deep cerebellar nuclei to trigger the CR

Question 27

What 2 things do complex spikes in Purkinje cells show?

Answer 27

• positive prediction error to US before training i.e. outcome is better than expected, enhanced learning
• negative prediction error to CS alone after training i.e. outcome is worse than expected, weakened learning

Question 28

When do dopamine neurons show phasic firing?

Answer 28

when there is a surprising or unexpected event; firing rate is increased in response to a positive prediction error and decreased in response to a negative prediction error

Question 29

What is ocular dominance plasticity?

Answer 29

the brain’s ability to change the strength of input from each eye to the visual cortex

Question 30

Which properties first arise in V1?

Answer 30

• orientation selectivity
• binocular responses

Question 31

What is the result of closing an eye during the critical period?

Answer 31

• V1 responses are shifted to favour the open eye
• ocular dominance columns of the closed eye are shrunk
• ocular dominance columns of the open eye are expanded