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Abstract:
Abstract: We assessed the semantic knowledge of three
patients with bilateral medial temporal lobe damage and variable
damage to lateral temporal cortex. The patients performed more
poorly than controls at confrontation naming, at pointing to an
item (e.g., ostrich, harp, seahorse) when given its name, and at
providing the name of an item when it was described. They also
answered fewer questions than controls about attributes of the test
items and gave impoverished definitions of the items as assessed by
blind raters. Two additional tasks were intended to minimize the
effects of anomia: pointing to an item when it was described, and
defining an item in response to seeing a picture of it. The
patients also performed more poorly than controls on these tasks.
In summary, the patients exhibited a mild to moderately severe
impairment of semantic knowledge. The impairment was not nearly so
severe as has been described in the syndrome of semantic dementia.
We suggest that damage to cortical areas lateral to the medial
temporal lobe, including the fusiform gyrus, is responsible for the
impairment. First, for one of our patients (E.P.), damage to the
anterior fusiform gyrus is the primary pathology outside the medial
temporal lobe (though the volume of more lateral cortex is also
reduced). Second, the amnesic patient H.M. has limited damage
outside the medial temporal lobe, and on confrontational naming he
performs within the normal range. Third, severe atrophy of the
lateral inferotemporal cortex is known to impair semantic
knowledge.
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