10 - Localisation of Learning

Question 1

What are the three types of experiments that demonstrate there are multiple memory systems?

Answer 1

1. Place Strategy (access whole maze, need fornix)
2. Conditioned Cue Preference (training with one arm with cheese and one without. Amygdala needed to learn)
3. Response Strategy (four arms with food, learn sequence, need caudate nucleus)

Question 2

What part of the brain is larger in London taxi drivers?

Answer 2

Hippocampus and more activation during navigation task

Question 3

What type of experiment and what part of the brain is damaged when testing spatial navigation?

Answer 3

Morris Water Maze and damaging hippocampus

Question 4

What are hippocampal place cells?

Answer 4

Neurons that have receptive fields that identify with specific locations in specific environments.

They fire when in a specific part of an environment

Question 5

What types of receptive fields do hippocampal place cells have?

Answer 5

Allocentric (defined by relations among objects)

Question 6

Where are the hippocampal place cells located in the brain?

Answer 6

CA1 - CA3 regions and dentate gyrus

Question 7

Do individual hippocampal place cells uniquely code for particular locations?

Answer 7

No, pattern of activity across multiple cells does.

Each cell can be active in more than one environment.

Question 8

Are hippocampal cells sensitive to direction?

Answer 8

Some are and some are not.

Direction-sensitivity influenced by relevance of direction to ask (finding food in specific sequence vs randomly scattered)

Question 9

How stable are hippocampal place cells?

Answer 9

Very stable, established within a few minutes of being introduced to novel environment and can be maintained for up to several months.

Question 10

Where do the inputs to the hippocampal place cells come from?

Answer 10

Entorhinal Cortex

Different types of cells provide building blocks for allocentric representations

Question 11

How do neurons in the medial entorhinal cortex respond to a rat’s movement?

Answer 11

Follows a lattice or grid.

Retain grid layout despite changes in speed or direction of movement.

Question 12

Explain the pattern of grid cells in the MEC

Answer 12

Pattern arises from instrinsic nature of network connections in MEC

Single grid cell provides ambiguous information about location, but can be resolved by combining across multiple grid cells.

Question 13

Overall, what is the main role of the hippocampus?

Answer 13

Spatial processing

But this is fundamental for many types of learning and memory (episodic, working memory)

Question 14

Describe the most predominate experiment paradigm in cerebellar learning

Answer 14

Eye-blink Conditioning

Rabbit hears a noise (CS) followed by air puff to eye (US)

After 30-40 trials, rabbit learns to blink in response to noise.

Question 15

What parts of the brain are involved in the eye-blink response and then added in the CR circuit?

Answer 15

Normal UR->US
- Puff signal travels down trigeminal nerve to the trigeminal nucleus and cranial motor nucleus. The blink goes to the same nucleus through the abducens nerve.

Conditioned response

• Red nucleus in brainstem
• Pontine nuclei in brainstem
• Inferior olive in brainstem
• Cerebellum

Question 16

What is the role of the red nucleus in the eye-blink conditioned response?

Answer 16

Connected to cranial motor nucleus

Stimulation induces eye-blink

Critical for expression of CR, not learning

Question 17

What is the role of the pontine nuclei in the eye-blink conditioned response?

Answer 17

Received input from auditory nucleus in brainstem, output to Cb

Neurons respond to sound.

Part of pathway conveying CS input

Question 18

What is the role of the inferior olive in the eye-blink conditioned response?

Answer 18

Receives input from trigeminal nucleus, output to Cb

Part of path conveying US input

Question 19

What is the role of the cerebellum in the eye-blink conditioned response?

Answer 19

Received converging input from pontine nuclei and inferior olive; output to red nucleus.

Get conditioning with combined stimulation of pontine nuclei and olive.

Lesion prevents learning, and blocks expression of previously learned CR

Question 20

What happens if the red nucleus is inactivated temporarily during eye-blink conditioned response training?

Answer 20

Prevents development of CR to CS (extinction), but once inactivation reversed, CR spontaneously reappears.

Question 21

What can electrical stimulation of the pontine nucleus achieve in eyeblink conditioning?

Answer 21

Serve as effective CS (instead of CS) when paired with air puff US

Question 22

What can electrical stimulation of the inferior olive do?

Answer 22

Elicits eye-blink and serve as US (instead of air puff) if paired with tone

Question 23

What do lesions to the inferior olive affect in eye-blink conditioning?

Answer 23

Prevents learning, but no effect on previously learned CS (-> induces extinction)

Question 24

In terms of parallel fibres and purkinje cells, how can conditioning be achieved?

Answer 24

Conditioning obtained by combined stimulation of parallel fibres on surface of Cb and deeper purkinje cells.

Potential for many CSs to be associated with one US as each purkinje cell received input from 100,000+ parallel fibres of granule cells and one climbing fibre (from inferior olive)