Memory Loss In Monkeys And Man

Question 1

What type of data generated the initial interest in the hippocampus

Answer 1

Human data

Question 2

What human case radically transformed the study of learning and memory

Answer 2

The case of patient H.M.

Question 3

Before H.M., what area of the brain did studies of learning and memory focus on

Answer 3

The cerebral cortex

Question 4

Where were H.M.’s lesions centred on

Answer 4

The hippocampus

Question 5

How did H.M’s hippocampal lesion occur

Answer 5

1933 knocked down by bicycle. Remained unconscious for five minutes.
Three years later started to have minor epileptic fits (first major fit at 16).
Condition gradually became worse with 10 minor, and 1 major fit per week.
Drugs were not effective and could no longer function in his job.
Underwent surgery at age 27 to remove 2/3 of the anterior hippocampus, bilaterally.

Question 6

Why was H.M’s surgery considered a success

Answer 6

Seizures became controllable by anticonvulsants

Question 7

Where is the hippocampus located

Answer 7

Medial temporal lobe

Question 8

Why is the hippocampus so prone to epilepsy

Answer 8

Far fewer inhibitory neutrons compared to the cortex

Question 9

Who performed psychological tests on H.M.

Answer 9

Dr. Brenda Milner

Question 10

What memory deficits did H.M. have after surgery

Answer 10

Complete anterograde and partial retrograde amnesia.
Selective problem with declarative memory - particularly episodic memory - and spatial memory - couldn’t navigate around his house or encode new spatial memories

Question 11

What type of memory is typically spared in MTL amnesics

Answer 11

Procedural memories - new skills can be learnt, expressed and retained by MTL amnesics

Question 12

What type of tests showed H.M’s impairment for encoding new declarative memories

Answer 12

Tests for spatial learning, short stories, jokes, lists of words or numbers, pictures, new words etc…
Scored almost zero on all of these tests

Question 13

What did the mirror drawing task show about H.M’s memory impairment

Answer 13

He is not impaired on the acquisition of new motor skills, although he cannot remember learning these new skills

Question 14

Describe the mirror drawing task

Answer 14

Participant given two concentric outlines of a star
Task is to draw an outline between the two stars
Can only look at hand and stars via a mirror
Errors scored as the number of times the concentric outlines are crossed

Question 15

Describe H.Ms performance on the mirror drawing task over 3 days

Answer 15

Day 1 performance poor - started at 30 errors

Day 3 performance almost perfect (pretty much same as a normal person would do)

Question 16

What is retrograde amnesia

Answer 16

Poor memory for items / events that occurred before time of trauma

Question 17

What is anterograde amnesia

Answer 17

Inability to encode new memories after trauma / surgery

Question 18

In what two ways is H.Ms memory loss important

Answer 18

It is selective for memory loss (as opposed to other high level perceptual, motor and cognitive functions)

It is selective to a particular domain of learning and memory - declarative memory

Question 19

What did Cohen and Squire propose were the two dissociable forms of memory

Answer 19

Declarative and procedural

Question 20

In their proposed taxonomy, what did Cohen and Squire break down declarative memories into

Answer 20

Episodic (memory for experiences)

Semantic( memory for facts)

Question 21

In their proposed taxonomy, what did Cohen and Squire break down procedural memories into

Answer 21

Skill learning
Priming
Conditioning

Question 22

What region of the brain does declarative memory rely on

Answer 22

The medial temporal lobe

Question 23

What regions of the brain does skill learning rely on

Answer 23

Basal ganglia, motor cortex and cerebellum

Question 24

Why can MTL amnesics still learn new skills, despite not having memory for learning these skills

Answer 24

Because the areas indicated in the procedural memory system (basal ganglia, motor cortex, cerebellum) are not affected in MTL amnesics

Question 25

How did MTL amnesics facilitate this idea of different memory systems

Answer 25

Dissociation between declarative memory and procedural memory impairment

Question 26

Apart from procedural memory, what type of memory is intact in H.M.
What type of task is this demonstrated by

Answer 26

Perceptual memory.

The Gollins picture task

Question 27

Describe the Gollins picture task

Answer 27

20 drawings of familiar objects are presented as a series of 5 cards, ranging from ‘most fragmented’ (hardest) to ‘least fragmented’ (easiest).
Each trial consists of less fragmented versions of the drawings being shown (trial 1 = most fragmented, last trial contains complete pictures).
Test & re-test method (re-test occurs 1 hour after first test)
Record the number of errors made for each trial in the test and retest phases.
Perceptual memory is displayed as the ability to identify less-complete versions of the drawings at re-test.

Question 28

Describe the results of the Gollins picture task for normal subjects and H.M

Answer 28

At first test, no difference in performance between H.M and normal participants.
At re-test, H.M’s performance hasn’t improved as much as normal participants but still shows a high level of retention (but has no memory of seeing these drawings in the initial training)

Question 29

What does patient R.B provide the clearest evidence for

Answer 29

Specific hippocampal involvement in anterograde amnesia

Question 30

What region of R.B’s hippocampus was destroyed. How did this occur

Answer 30

Area CA1 was destroyed.
R.B had a heart attack age 52.
Temporary cessation of blood circulation caused ischaemia and resulted in brain damage

Question 31

How was R.B’s memory affected by the hippocampal damage

Answer 31

Total anterograde amnesia

2-3 years retrograde amnesia

Question 32

Squire and Zola-Morgan created a delayed non-match to sample task to investigate animal models of amnesia. Describe this task

Answer 32

Monkeys presented with a sample object, which when displaced, reveals a food pellet
After a variable delay (seconds to minutes) the monkey is presented with the original object and another object.
The food is always present under the object that differs from the sample.
Over a series of trials with different pairs the monkey learns this rule

Question 33

What MTL lesions did Squire and Zola-Morgan create in macaque monkeys in their DNMTS task. How did this affect the monkey’s performance. What human patients were these lesions similar to

Answer 33

Hippocampal lesion (H) (similar to R.B.) - deficit in performance

Extended lesion to include adjacent entorhinal cortex and parahippocampal cortices (H+) - stronger effect on DNMTS learning

Extended lesion forward to include anterior entorhinal cortex and perirhinal cortex (H++) (similar to H.M) - even stronger effect on DNMTS learning

Question 34

What type of lesioned animals did Squire and Zola-Morgan use to see whether the period of delay in their DNMTS task had an affect on memory

Answer 34

H++ (hippocampus and entorhinal and perirhinal cortices)

Question 35

In Squire and Zola-Morgan’s DNMTS task, how did short sample-test delays affect the H++ macaques

Answer 35

These macaques attained normal performance, showing preserved short-term memory (MTL amnesics also show this)

Question 36

In Squire and Zola-Morgan’s DNMTS task, how did long sample-test delays affect the H++ macaques

Answer 36

These macaques were impaired (as are MTL amnesics). The extent of this impairment increases with delay length

Question 37

What does good performance in H++ monkeys on the short delays in Squire and Zola-Morgan’s DNMTS task suggest about the MTL

Answer 37

The MTL is not required for short-term memory

Question 38

What test (animal)shows that the MTL is not required for procedural memory

Answer 38

Get H++ monkey to retrieve polo mint from behind a screen. Ability to complete the task improves with experience.
Get H++ monkey to retrieve polo mint from behind a screen with a coat hanger. Ability to complete task also improves with experience
No difference in performance between H++ and normal monkeys on these tasks

Question 39

Describe the study used to demonstrate the retrograde gradient of amnesia in H++ monkeys. What can you conclude the MTL is not required for

Answer 39

Monkeys presented with pairs of novel objects, where one object within each pair was reinforced with food.
Animals acquired memory for 100 object-food pairings over 4 months.
Hippocampus and associated cortices (H++) then lesioned in half of the monkeys.
All animals tested two weeks later.
For the normal monkeys, performance was very good for pairs presented two weeks before the surgery, and good for pairs presented 4 months before the surgery.
For the H++ monkeys, performance was very poor for the pairs presented two weeks before surgery, but good (same as non-lesioned monkeys) for pairs presented 4 months before the surgery.
Lesioned monkeys show retrograde gradient of amnesia (as does H.M) - very old memories preserved but memories encoded closer to the time of insult less well preserved.
This suggests that memories are present in the hippocampus for the short term, and are then transferred somewhere else.
Can conclude that the MTL is not required for long-term memory

Question 40

What does the extent of retrograde amnesia correlate with in MTL patients?

Answer 40

The extent of hippocampal damage

Question 41

Which MTL amnesics only suffered damage to CA1? How many years did their retrograde amnesia extend?

Answer 41

R.B and D.G. 2-3 years retrograde amnesia

Question 42

Which MTL amnesics suffered 40-50 years retrograde amnesia

Answer 42

L.M and W.H

Question 43

What type of hippocampal damage did patient E.P have? What was the extent of their retrograde amnesia?

Answer 43

Complete hippocampal damage (including some surrounding tissue). 40-50 years retrograde amnesia

Question 44

What commonalities do all MTL amnesics share. What does this suggest about the human MTL?

Answer 44

Anterograde amnesia is always more severe than retrograde.
All patients have access to childhood memories.
MTL not required for long-term memories.

Question 45

In summary, what three things does MTL damage in macaques and humans have NO effect on? What is the proposed role of the hippocampus and MTL

Answer 45

Short term memory
Long term memory
Procedural memory

Proposed role is to convert short-term memory into long-term memory