Schmolck et al. (2002) The Contemporary Study: Brain Damage In Patient H.M.

Background

  • Used brain damage patients

  • Used HM a well established brain damage patient who had his hippocampus removed after a bout of epilepsy
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Aims

  • To see if semantic LTM memory is linked to a particular part of the brain

  • If this was the case those patients with lesions on those parts of the brain would underperform in the tests

  • Focused on the MTL and hippocampus - the same as Raine

  • Looked in detailed at the patient HM

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Varibles

  • IV = The extent of brain injury

  • DV = The scores on 9 separate tests of semantic LTM

  • Natural experiment with matched pairs design

  • Type of cognitive test repeated measures design as every pps did each test

  • HM was considered separately from the rest of the pps as he had more widespread brain damage

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Sample

  • 6 with severe damage to the MTL

  • 8 controls with no brain damage

  • 3 of the 6 also had damage to the temporal cortex (MTL+)

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Procedure

  • There were 9 tests in total each was based on a set of 48 drawings:

    • half were animals

    • half were objects

    • They were grouped in sixes:

      • 6 domestic land animals

      • 6 foreign land animals

      • 6 birds

      • 6 musical instruments

      • 6 vehicles

      • 6 water creatures

      • 6 electrical household items

      • 6 non-electrical household items

  • The tests were things like:

    • Similar pictures - the pps were shown 6 pictures all having the same theme and asked to point out that the researcher names

    • Category fluency - The pps were asked to give as many examples of things that would feature in a given theme within a minute

    • Category sorting - the pps were asked to sort all 48 pictures into living and man-made categories

    • Definitions - the pps were shown a picture and asked to define it by the theme it fitted into

  • She also used some dementia tests, for example:

    • Pps were shown 30 pictures of real and non-real things and asked them to say whether it was real or not

  • The pps were all recorded and transcripted

  • 14 ‘raters’ checked each transcript for reliability and looked for grammar/syntax errors in the pps speech as this would also indicate trouble with semantic memory

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Results

  • Similar pictures:

    • controls got all the answers right as did those with only hippocampus damage (HM got 98% on living and 100% for non living)

    • MTL+ patients performed worse getting 85% for living and 90% for non living

  • MTL+ patients did significantly worse in all the tests

  • HM did better than MTL+ patients but slightly worse than MTL patients with only hippocampus damage

  • Overall Controls scored 99%, MTL patients (without HM) scored 100% and MTL+ patients scored 78%

  • There was a positive correlation between the more brain damage and number of mistakes as the MTL+ did the worse then HM and then hippocampus only (HO) patients

  • Although they were meant to be matched Schmolck suggests that the HO patients did better than the controls because they were younger

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Conclusions

  • There seems to be a link between the loss of semantic LTM and damage to the temporal cortex

  • HO patients only suffer a loss of episodic memory but not semantic

  • This suggests the two different types of memory are encoded in different parts of the brain with the hippocampus/MTL dealing with episodic and the nearby temporal cortex dealing with semantic

  • HM performed very similarly to the control pps but had lapses when defining things, where he closely resembled more the MTL+ group. This suggests his brain damage is very specific and was not like any of the other pps. There is issues with generalising his results however as he had a very unusual background where he spent much of his time from 10 in hospitals so missed a lot of school and came from a low sociometric background possibly stunting his development introducing an extraneous variable that could have affect his results.

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Evaluation - Strengths

  • G
  • She did single HM as an anomaly, meaning she ignored him when assessing the other categories and analysing his results in more detail

  • R

  • She used a standardized procedure that could be replicated by other researchers especially as MRI are more common.

  • She used 14 raters to check the pps scores, this gives the study inter-rater reliability

  • A

  • The main application for this study has been for other researchers to build upon her research to understand the brain’s role in memory. This has lead to the development of neurocognitive psychology

  • This study also demonstrates the risk of brain surgery and the side effects that damage may cause allowing doctors and patients to properly weigh up the pros and cons of surgical procedures

  • Could lead to a cure or development coping methods for people with damage like CW

  • V

  • The use of matched pairs design and healthy controls increases the validity, we can be reasonably sure that the different scores on the test are caused by the brain lesions in different parts of the brain not other factors like age or intelligence, this is also backed up by the MRI scans that show the temporal lobe area activating when patients had to make semantic judgements

  • E

  • The benefits gained from the study it outweighs the ethical issues as it has increased our understanding of brain function

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Evaluation - Weaknesses

  • G

  • Used a small sample only 3 HO patients, 3 with wider temporal cortex damage

  • Small samples can be easily distorted by anomlies (HM was the anomaly)

  • Brain lesions and memory problems of these kinds are quite rare, HM suffered from epilepsy and the MTL+ patients all suffered from herpes, this reduces the representativeness of the sample

  • R

  • Because she used pps with specific brain damage it is very hard to replicate the exact study especially as HM who was a large pull of focus in the study, died in 2008

  • V

  • There is low ecological validity in this study as the task was more like a game rather than a real life task and so is an artificial task lowering their ecological validity

  • E

  • The study featured pps that could not give valid informed consent meaning only presumptive consent could be gotten, increasingly ethicists regard it as unacceptable to treat the lack of refusal as tacit consent.

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