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Abstract:
One of the goals of cognitive neuroscience is to make
inferences about the functional and neuroanatomical substrates of
particular components of the cognitive system. In cognitive
neuropsychology these inferences are often made on the basis of
data about a patient's level of performance across behavioural
tasks. However, for some tasks it is not obvious on what basis a
reliable assessment of a patient's performance can be made. We
investigate this issue in relation to the copying and drawing from
memory of simple common objects - tasks that are frequently used to
investigate potential visual processing deficits. Analyses of
performance in these tasks are most often based solely on
descriptive judgements about a patient's overall performance.
However, there are several grounds for arguing that this type of
analysis is inadequate. One concern is that it does not make
reference to normative data. Consequently, seemingly poor
performance shown by a patient, which might otherwise be attributed
to a functional impairment, may well be within the normal range of
performance on all or some relevant task dimensions (e.g., spatial
configuration and feature structure). We describe a quantitative
analysis technique that allows a patient's performance in copying
and drawing from memory to be compared to the distribution of
performance shown by neurologically normal control subjects on
several different theoretically motivated task dimensions.
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