Lecture 6- Learning and Memory in Mammals I

Question 1

Define learning

Answer 1

• A change in behaviour that rests from acquiring new knowledge
• The strengthening of responses or the formation of new responses to stimuli due to repetition or practice

Question 2

Define memory

Answer 2

• Process by which knowledge is encoded, stored and retrieved for later use
• Knowledge is gained through learning

Question 3

What are the two dimensions of memory

Answer 3

Temporality (time):
- The time course of information storage

Nature of the information stored

Question 4

Working memory

Answer 4

• On task memory, task specific
• Limited capacity system that temporarily holds information.
• Important for reasoning and guiding decision making behaviour.
• Distinct from STM as allows stored information to be updated/manipulated
• Limited capacity- few bits of information at one time that are deleted after use
• If the information is lost due to distraction there is no retrieval

Question 5

What is the classic rodent working memory task?

How does it work?

Answer 5

• 8-arm radial maze test
• Every arm is baited with a piece of food and animals are free to explore arms but to be efficient have to remember during the task which arm has already been visited.
• This information is of no value after the task has been completed- memory is reset for next task

Question 6

Describe short term memory

Answer 6

• Milliseconds to minutes e.g., remembering a phone number to call later
• Storage of information but information is not manipulated.
• Limited capacity (approx. 7 items)
• Often data rich
• Not suitable to store all information in LTM that is the reason for STM.
• STM is selectively transferred over to LTM

Question 7

Describe long term memory

Answer 7

• How did you celebrate your 18th birthday?

- Two forms of LTM: Explicit and Implicit

Question 8

Describe Explicit/ Declarative LTM

Answer 8

• Explicit is conscious memory
• Episodic events and semantic (facts)
• It is flexible- multiple pieces of information under different circumstances

Question 9

Describe Implicit/ Non declarative LTM

Answer 9

• Implicit- automatic and conscious
• Knowledge about how to perform something
• Can be associative or non-associative
• Inflexbile- highly connected to conditions under which the learning occurred e.g., Associative learning

Question 10

Why do we mainly look at implicit memory in Drosophila?

Answer 10

• Easy to quantify
• Implicit looks at knowledge about how to perform something
• It is harder to get drosophila to remember where it experienced something

Question 11

Which model organisms do we study explicit learning in?

Answer 11

• Rodents

- Explicit learning- rodents can remember where it experienced something.

Question 12

What is habituation?

Answer 12

• An example of non associative implicit memory
• Habituation is the decrease in response to a benign stimulus through repeated presentation of the stimulus.
• This is an active process, not a passive loss of activity

Question 13

What is sensitisation

Answer 13

• An enhanced response to multiple different stimuli after presentation to noxious or intense stimulus.
• Important to focus on relevant information (increasing signal to noise ratio).
• e.g., cocktail party phenomenon someone mentioning your name in a conversation

Question 14

What are the two types of non associative implicit memory?

Answer 14

• Habituation

- Sensitisation

Question 15

What is associative implicit learning?

Answer 15

• Learning about the relationship between a stimulus and a response or between two stimuli.

Question 16

Describe Pavlovian/ Classical conditioning

Answer 16

• Conditional stimulus (CS) (bell ringing) elicits no response.
• Unconditioned stimulus (smell of food) elicits salivation.

When the US and CS are paired together in close sequence then the dog will eventually respond to the ringing of the bell alone.
(after repetition)

Question 17

What is operant conditioning?

Answer 17

• Trial and error learning
• Random activity becomes paired with reinforce (positive or negative).
• Complex behaviour e.g., pressing a lever becomes paired with positive reinforcers e.g., food.
• Or with negative stimuli e.g., a loud bang/ bright light/ shock.
• More likely to press the lever again if they get a positive reinforcer.

Question 18

What are the two types of associative implicit memory?

Answer 18

• Operant conditioning (BF Skinner)

- Pavlovian conditioning/ Classical conditioning

Question 19

4 Distinct Operations of Explicit learning

Answer 19

1. Encoding: Paying attention in the environment to relevant information and we link that information with an existing memory of something we are already familiar with. This process if influenced by motivation
2. Storage: Neural mechanisms by which memory is retained over time (L7). Memory is easy to disrupt here
3. Consolidation: Temporary and labile information becomes more stable. Involves gene expression changes, protein synthesis and structural synaptic changes.
   - Info is integrated into already existing neural networks.
   - There is a new concept of consolidation of LTM into neural networks (systems consolidation).

Retrieval: Conscious retrieval of memory we have formed.

Re-retrieval: Debate ongoing if there is a 5th stage.
- People have found when you have retrieved a memory you can manipulate it (i.e., it becomes slightly more labile and can change the way it is encoded).

Question 20

Describe the 5-choice serial reaction time task

Answer 20

• Rat nose poke box undertaking 5-choice serial reaction time task.
• Can measure how impulsive or attention.
• Holes light up and animal associates this with a food award.

Question 21

List the four distinct operations/ stages of explicit learning

Answer 21

• Encoding
• Storage
• Consolidation
• Retrieval
• Re consolidation

Question 22

Who was patient HM?

Answer 22

• Most important man in learning and memory
• Uncontrollable temporal lobe epilepsy so they removed his temporal lobe
• Bilateral lesions of the temporal lobes (including hippocampus, amygdala and cortex).
• Same IQ
• Working memory intact,
• Semantic (fact) memory was normal
• No evidence of retrograde amnesia (so remembered childhood events)
• Intact motor skills (mirror tracing task) but would forget that he had done the same task the day before.
• Patient HM had devastating anterograde amnesia (trouble making new memories). Because new STMs are not converted into LTM.

Question 23

What did studies on patient HM show?

Answer 23

• Memory is a distinct cerebral function separate from other cognitive and perceptual functions.
• He gave us indications of the role of the medial temporal lobe (hippocampus, amygdala, adjacent parahippocampal cortex) plays an important role in memory formation.

Question 24

What type of memory is the neocortex involved in?

Answer 24

Neocortex (all of cortical regions)- store LTM

• Tends to be specialised memories specially stored in pieces of the cortex that process that information.
• E.g., visual cortex (occipital lobe) processes visual information and visual memories are stored here

Question 25

What type of learning and memory is the prefrontal Cortex involved in?

Answer 25

• High level cognitive functions

- Working memory and influences memory retrieval from other neural systems in the brain

Question 26

What type of learning and memory is the parietal lobe involved in?

Answer 26

• Navigation

Question 27

What type of learning and memory is the Cerebellum involved in?

Answer 27

• Motor memory

e. g., riding a bike

Question 28

What type of learning/memory is the occipital lobe involved in?

Answer 28

Visual processing

Question 29

What type of learning/memory is the temporal lobe involved in?

Answer 29

• Hippocampus- memory encoding, consolidation and retrieval, spatial memory in rodents
• Amygdala- emotional memory

Question 30

Why does the hippocampus form a huge amount of the rodents brain?

Answer 30

• The hippocampus is involved in spatial learning.

- Rodents are scavengers they Mao the environment to find food/avoid predators so need good spatial memory.

Question 31

How can we investigate the hippocampus?

Answer 31

• Using electrophysiology

- The HC has a clearly defined neural circuitry that has been mapped out

Question 32

Describe the Water Morris Maze

Answer 32

• Developed as a simple spatial task that involves olfactory (smell) cues in the maze
• Animals are trained to find a submerged platform to escape from the water
• First trial animal doesn’t know where the platform is so swims randomly.
• But on next trial, if it knows where the platform is and its paths to the platform becomes shorter and it gets there more quickly

ACQUISITON PHASE:

• The time to find the platform is recorded (latency) and this reduces with the number of training days.

The length of the swim path is also measures (distance- by a video tracker system) this decreases with the number of training days.

So we can measure animals rate of learning (Control animals vs mouse model with amyloid B in brain)

MEMORY RECALL:

• Take out the platform and see where the animal is searching.
• If a memory has been formed then the animals should spend more time in the quadrant where the platform used to be.
• Impaired rats with hippocampal legions have random searching path.

Question 33

What happens in rodents that have lesions in the hippocampus?

Answer 33

• Impaired association learning, spatial learning and memory and memory consolidation. (from STM–> LTM).

Question 34

In humans what do lesions in the hippocampus cause?

Answer 34

• Impair the transfer of short term memory to long term meory
• A problem with encoding or consolidation
• E.g., patient HM