Memory Loss In Monkeys And Man Flashcards
What type of data generated the initial interest in the hippocampus
Human data
What human case radically transformed the study of learning and memory
The case of patient H.M.
Before H.M., what area of the brain did studies of learning and memory focus on
The medial temporal cortex
How did H.M’s hippocampal lesion occur
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.
Why was H.M’s surgery considered a success
Seizures became controllable by anticonvulsants
Where is the hippocampus located
Medial temporal lobe
Why is the hippocampus so prone to epilepsy
Far fewer inhibitory neutrons compared to the cortex
Who performed psychological tests on H.M.
Dr. Brenda Milner
What memory deficits did H.M. have after surgery
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
What type of memory is typically spared in MTL amnesics
Procedural memories - new skills can be learnt, expressed and retained by MTL amnesics
What type of tests showed H.M’s impairment for encoding new declarative memories
Tests for spatial learning, short stories, jokes, lists of words or numbers, pictures, new words etc…
Scored almost zero on all of these tests
What did the mirror drawing task show about H.M’s memory impairment
He is not impaired on the acquisition of new motor skills, although he cannot remember learning these new skills
Describe the mirror drawing task
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
Describe H.Ms performance on the mirror drawing task over 3 days
Day 1 performance poor - started at 30 errors
Day 3 performance almost perfect (pretty much same as a normal person would do)
What is retrograde amnesia
Poor memory for items / events that occurred before time of trauma
What is anterograde amnesia
Inability to encode new memories after trauma / surgery
In what two ways is H.Ms memory loss important
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
What did Cohen and Squire propose were the two dissociable forms of memory
Declarative and procedural
In their proposed taxonomy, what did Cohen and Squire break down declarative memories into
Episodic (memory for experiences)
Semantic( memory for facts)
In their proposed taxonomy, what did Cohen and Squire break down procedural memories into
Skill learning
Priming
Conditioning
What region of the brain does declarative memory rely on
The medial temporal lobe
What regions of the brain does skill learning rely on
Basal ganglia, motor cortex and cerebellum
Why can MTL amnesics still learn new skills, despite not having memory for learning these skills
Because the areas indicated in the procedural memory system (basal ganglia, motor cortex, cerebellum) are not affected in MTL amnesics
How did MTL amnesics facilitate this idea of different memory systems
Dissociation between declarative memory and procedural memory impairment
Apart from procedural memory, what type of memory is intact in H.M.
What type of task is this demonstrated by
Perceptual memory.
The Gollins picture task
Describe the Gollins picture task
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.
Describe the results of the Gollins picture task for normal subjects and H.M
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)
What does patient R.B provide the clearest evidence for
Specific hippocampal involvement in anterograde amnesia
What region of R.B’s hippocampus was destroyed. How did this occur
Area CA1 was destroyed.
R.B had a heart attack age 52.
Temporary cessation of blood circulation caused ischaemia and resulted in brain damage
How was R.B’s memory affected by the hippocampal damage
Total anterograde amnesia
2-3 years retrograde amnesia
Squire and Zola-Morgan created a delayed non-match to sample task to investigate animal models of amnesia. Describe this task
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
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
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
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
H++ (hippocampus and entorhinal and perirhinal cortices)
In Squire and Zola-Morgan’s DNMTS task, how did short sample-test delays affect the H++ macaques
These macaques attained normal performance, showing preserved short-term memory (MTL amnesics also show this)
In Squire and Zola-Morgan’s DNMTS task, how did long sample-test delays affect the H++ macaques
These macaques were impaired (as are MTL amnesics). The extent of this impairment increases with delay length
What does good performance in H++ monkeys on the short delays in Squire and Zola-Morgan’s DNMTS task suggest about the MTL
The MTL is not required for short-term memory
What test (animal)shows that the MTL is not required for procedural memory
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
Describe the study used to demonstrate the retrograde gradient of amnesia in H++ monkeys. What can you conclude the MTL is not required for
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
What does the extent of retrograde amnesia correlate with in MTL patients?
The extent of hippocampal damage
Which MTL amnesics only suffered damage to CA1? How many years did their retrograde amnesia extend?
R.B and D.G. 2-3 years retrograde amnesia
Which MTL amnesics suffered 40-50 years retrograde amnesia
L.M and W.H
What type of hippocampal damage did patient E.P have? What was the extent of their retrograde amnesia?
Complete hippocampal damage (including some surrounding tissue). 40-50 years retrograde amnesia
What commonalities do all MTL amnesics share. What does this suggest about the human MTL?
Anterograde amnesia is always more severe than retrograde.
All patients have access to childhood memories.
MTL not required for long-term memories.
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
Short term memory
Long term memory
Procedural memory
Proposed role is to convert short-term memory into long-term memory
