lecture 10 - Learning, memory and behaviour

Question 1

Types of memory

Answer 1

Question 2

Different memories, but the same type:

Answer 2

declarative

Question 3

Episodic

Answer 3

Memories of specific events (e.g. my wedding).

Question 4

Semantic

Answer 4

• Knowledge of facts about the world.
• Can be derived from episodic memory (e.g. my experiences of specific cats combine to produce a semantic representation of what a cat is).

Question 5

Different memories, but the same type:

Answer 5

procedural

Question 6

Non-declarative (implicit) memory

Answer 6

Procedural
Priming
Classical conditioning
Non-associative learning

Question 7

Procedural

Answer 7

How to do things (e.g. juggling).

Question 8

Priming

Answer 8

Exposure to one stimulus influences a response to a subsequent stimulus.
- Priming example: faster recognition of the word “NURSE” if preceded by the word “DOCTOR” rather than (for example) “BREAD”

Question 9

Classical conditioning

Answer 9

Pairing of stimulus-response associations (e.g. Pavlov’s dogs: a bell and salivation).
: Pavlov showed that if he paired an ‘unconditioned stimulus’ (food) with a ‘conditioned stimulus’ (a metronome) after a few learning trials he could produce a ‘conditioned response’ (salivation) in the absence of food

Question 10

Non-associative learning:

Answer 10

Habituation – if a snail is moving along a surface, if the experimenter taps the surface the snail withdraws into its shell. If this is repeated, eventually the snail stops withdrawing
Sensitisation – marine worm Nereis – if kept in small tube and fed at regular intervals, becomes much more likely to response to ANY novel stimuli with food seeking behaviour

Question 11

Parts of the CNS associated with different types of memory

Answer 11

Question 12

The hippocampus

Answer 12

a hub for declarative memory

Question 13

How do we know that the hippocampus is important for declarative memory? - Patient HM (Henry Molaison)
- Schoville and Milner (1957)

Answer 13

• Bilateral medial temporal lobectomy to control severe epilepsy.
  After surgery:
  Could still remember events from the past.
• Long-term memory intact.
  Could participate in short conversations.
• Short-term memory intact.
  Could learn new skills.
• Procedural memory intact.
  Could not form new declarative memories.

Question 14

Anatomy of the hippocampus

Answer 14

Inputs:
- Mainly from structures in the parahippocampal gyrus (entorhinal cortex).

Outputs:
- Entorhinal cortex.
- Fornix.

Question 15

Circuitry of the hippocampus

Answer 15

A trisynaptic circuit

Question 16

Outputs of the hippocampus

Answer 16

Question 17

Fimbria

Answer 17

becomes continuous with the fornix

Question 18

Fornix

Answer 18

connects the hippocampus to the mamillary bodies.

Question 19

Hippocampal commissure

Answer 19

hippocampal fibres cross between the two hippocampi

Question 20

Cortico-hippocampal information flow diagram

Answer 20

Question 21

Cortico-hippocampal information flow

Answer 21

• Parahippocampal cortex – site of convergence of cortical input.
• Information relayed to the hippocampus where associations formed.
• Information output from the hippocampus back to parahippocampal cortex.

Question 22

Investigating memory using animal models

Answer 22

• Other mammals (including rodents) have a hippocampus (and other conserved medial temporal lobe structures).
• We can manipulate (lesion, inactivate) these and examine the effect on memory.

Question 23

How do we study memory in rodents?

Answer 23

We can take advantage of their natural behaviours to test memory, i.e.
Novelty preference (curiosity to explore)
Food seeking
‘Freezing’ when afraid
Avoidance of ‘dangerous’ situations

Question 24

The Morris water maze – a test of spatial memory

Answer 24

Question 25

Lesions of the hippocampus impair spatial memory

Answer 25

Question 26

Blockade of NMDA receptors in the hippocampus impairs LTP in rats in vivo

Answer 26

Question 27

…and blocks spatial memory in the water maze

Answer 27

Antagonism of hippocampal NMDA receptors blocks preference for the target quadrant This shows that rats treated with D-AP5 (but not L-AP5) cannot learn the location of the hidden platform.

Question 28

Pharmacological inactivation of the hippocampus blocks retrieval of existing spatial memories

Answer 28

- Mice trained to search for a hidden escape platform in the Morris water maze. - Then muscimol (GABAA receptor agonist) infused into CA1 of hippocampus to temporarily inactivate it.

Question 29

Is the hippocampus involved in spatial memory in people?

Answer 29

- fMRI imaging during virtual navigation task around London’s Soho district. - Activity in the hippocampus positively correlates with distance to the goal location during active (but not passive) navigation.

Question 30

Recognition memory

Answer 30

Recognition memories are memories for things that are familiar.

Question 31

Investigating visual recognition memory in animals

Answer 31

- Measure the amount of time that the animal spends exploring each object. - Relies on rodent’s natural inquisitiveness: novelty preference.

Answer 32

Question 33

The perirhinal cortex is important for object recognition memories

Answer 33

Lesions of the perirhinal cortex (PRH) but not hippocampus (HPC) or medial prefrontal cortex (mPFC) impair novel object preference memory.

Question 34

Perirhinal cortex

Answer 34

- Perirhinal cortex is located adjacent to the hippocampus in the medial temporal lobe. - Perirhinal cortex directly and indirectly innervates the hippocampus.