STUDY; SEMANTIC KNOWLEDGE, SCHMOLCK 2002

Aim

Investigate the effects of bilateral brain damage (medial temporal lobe (MTL) + anterolateral temporal lobe) on semantic knowledge in people with amnesia.

Design

• Quasi experiment; IV is not directly manipulated, no random allocation, grouped based on a pre-existing trait. Doesn’t show causation

• IV; kind of brain damage (3 levels)

• DV; semantic memory

Sample

• 8 control participants (healthy male volunteers, matched by age/education)

• 6 amnesiac patients (5 male, 1 female)

→ MTL+; 3 with extensive MTL damage and variable damage to the lateral temporal cortex

→ HF; 2 with lesions to the hippocampal formation

→ PATIENT HM; damage mostly on MTL + additional damage to the anterolateral temporal cortex

Tasks for participants

Involved identifying line drawings of living/non-living objects;

• point at the picture from it’s name / description

• naming the item in the picture

• naming an item from its description

Results

• MTL patients + HM provided un detailed definitions with a significant amount of errors

• MTL patients + HM had a strong correlation between performance + extent of damage to the lateral temporal cortex

• MTL / anterolateral temporal cortex had mild/moderate impairment on the tests

• HF patients performed better than other groups

→ HF; 100% correct over the naming/identifying tests

→ MTL; 78% correct over the naming/identifying tests

Conclusions of the study

• deficits in semantic knowledge are most likely related to cortical damage lateral to the MTL

• there’s a relationship between the extent of damage to the lateral temporal cortex & performance

• patients with damage limited to the HF performed normally

Strengths

• INTER-RELIABILITY; 14 raters to check definitions on a test. reduced bias/subjectivity on interpretations, conclusions are more reliable

• APPLICABILITY; gives neurosurgeons a detailed map of areas to avoid when removing a tumor so crucial cognitive functions aren’t affected. value is not just theoretical understanding but also practical applications to medicine

• VALIDITY; higher objectivity- scoring system for participant responses. no researcher bias

Limitations

• LOW EV; the task of naming/categorizing pictures lacks mundane realism- doesn’t represent semantic recognition of items in real scenarios (people don’t usually categorize pictures of common items)

• LOW PV; 6 participants with damage unique to them (3 with MTL/hippocampus damage, 3 with temporal cortex damage) + a limited sample size of mostly men limits generalizability to other genders & a wider population

• VALIDITY; participant variables- we do not know the cognitive capabilities of patients before the brain injury. valid comparisons of data/results are impossible

Conclusion about the study

Key contribution to research stressing the importance of medial temporal lobes and the lateral temporal lobe in processing semantic memory.

However, it’s difficult for studies to establish that damage to specific areas of the brain is the cause for an impairment as the cognitive functions of the patients before the brain injury is unknown, so valid comparisons are impossible.