lec 8 (w9) - memory impairments

Question 1

evidence for localisation of memory in the brain?

Answer 1

Lashley and others had found no evidence for localisation of memory in the brain.

Memory impairments in animals appeared linked to extent of damage (removal of cortex) rather than site of damage

• Key case studies of individuals with memory impairments in the 20th Century changed understanding of memory and the brain fundamentally

Question 2

H.M.
-who was he
-what happened to him

Answer 2

Henry Molaison (1926 -
2008)

• Severe epilepsy after
  knocked down by bike at
  age 7 (could not function in every day life
• Surgery by William Scoville
  in 1953 (aged 27)

Question 3

HM’s surgery on epilepsy

Answer 3

-epilepsy is essentially waves of uncontrolled activity spreading across the brain
-it often comes from a particular source
-you go through a series of sessions wih an eeg cap, to find where the uncontrolled activity comes from
-the surgery can then remove that part of that brain- and it is generally pretty effective

-however with HM they could not localise where the activity was actually coming from (so normally you would not be able to do the operation)
-still went ahead with it based on Scoville’s experience, location that tended to be common in patients was the medial temporal lobe, including hippocampus
-removed a section bilaterally
-experimental operation

xrays show you white flecks on the brain (meta; staples left in his brain) - people didnt want to do imaging,

Question 4

HM: consequences of surgery

Answer 4

Seizures reduced (but not gone
completely)

• No personality change
• Preserved intelligence - indeed
  higher than before (IQ 112 vs 104)
• No deficits in perception, abstract
  thinking, reasoning, motivation
• Immediate and profound memory impairments
• Pattern of memory deficits revealed new insights into memory processes and suggested localised memory function in the brain

brenda miller went on to study the patient

Question 5

HMs memory impairments
-what can this tell about thr brain

Answer 5

-able to recall thinsg from before surgery
-was not able to lay down new memories from after the surgery (didnt remember the doctor surgery, or conversations )
- severe anterograde amnesia (big problem)

-some problems with 3 years leading up prior to surgery (mild retrograde amnesia

-he had issues making memories but not problems accessing old ones (already tells us there is a single dissociation in the brain)
-Medial temporal lobe (part that was removed) and especially the hippocampus -a key role for laying down new memories?

Question 6

HM’s problems after surgery
- knowledge of famous faces

Answer 6

Sharp decline in ability to recognise faces of people who became famous after his surgery

Question 7

Hms knowledge of famous faces
-new semantic memories ? semantic memories intact

Answer 7

Many early studies focussed on HM’s failure to lay down new episodic memories

• Some early evidence that new
  semantic memories could be formed (and so not impaired )

when he failed to recognise a face they gave him prompts

• Phonemic (e.g., initial letters)
• Semantic (e.g., what the person did)

found that once they prompted him, now the performance is good even for faces he could not recognise

Question 8

problems creating new semantic memories as well

Answer 8

Across word and famous name tests, new semantic memories severely impaired

• Also tested famous faces (as in
  Marslen-Wilson & Teuber, 1975) but
  only looked at semantic cues for recall
• Very little benefit of cuing
• BUT in all experiments performance for post 1950s stimuli was above chance
• Some new semantic memory must
  be laid down

Question 9

Short term memory and long term memory in patient HM

Answer 9

Normal digit span / working memory
* HM able to retain digit sequences for up to 15 minutes if able to rehearse - once stop rehearsal then lost
* could maintain a conversation

• STM does not involve MTL structures?
• Retention much shorter for more complex stimuli like faces - difficult to rehearse
  -so evidence we can put stm and ltm in different parts of the brain

Question 10

HMs motor memory

Answer 10

Able to learn motor skills

get a shape to trace from looking at mirror, have to keep pencil in between two tracks (a very hard task)

Hm’s error rate went down (like a normal person) but if you told him to do it on another day he would have no memory of the task but already be better at the task

• Suggests distinction
  (functional and anatomical)
  between motor learning and
  other memory systems

Question 11

HM and priming
-distractor/recognition task

Answer 11

Show target pattern to join dots and
ask participant to copy this onto dot
pattern
* Distractor task
* Then given dots and asked to join
them in any way they want to
* Look at how frequently they
produce the target patterns

• Recognition task - copy targets then 4AFC between patterns to ask
  which they had copied (3 mins)
  earlier

Hm did this task and produced similar patterns to previous (priming) even though he didn’t remember doing it
-but when you gave him patterns and asked if he had produced those in the first part of the experiment (recognition task) he really couldn’t do it

Question 12

HM- priming/perceptual learning

Answer 12

-gollins incomplete pictures task
-given a degraded fragmented line drawing and asked to identify what it is

-look at how many steps it takes to get to real drawing

-HM performed similar