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Abstract:
Brain damage can cause selective deficits for specific
categories of knowledge; the most common dissociation being between
living and non-living things. We report a PET (positron emission
tomography) investigation of patient JBR who has a well documented
category-specific deficit for living things. Six normal controls
and JBR were scanned during a word-picture matching task for i.
living things, and ii. nonliving things. A comparison of living
relative to nonliving things showed activation of three right
temporal areas (superior temporal, middle temporal and medial
temporal) in the controls and JBR. However, all six controls
significantly activated four areas that were not activated by JBR.
These were in the right anterior temporal pole, the temporo
occipital, the right inferior temporal and the right cerebellum.
Right temporal activations have previously been implicated in
object recognition tasks. We suggest that the right temporal lobe
may be involved in the increased object processing required for
living things which are more difficult to discriminate in view of
their structural similarities. Nonliving things, in contrast, tend
to have unique structures and are thus easier to differentiate. The
right temporal areas activated by the controls, but not JBR,
therefore appear to be crucial in successfully processing living
things.
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