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Abstract:
Abstract: In healthy subjects, cognitive representations of
familiar objects are reliably associated with categories of hand
shape (palm, pinch, clench, and poke), and these categories are
based on functional and not structural considerations. In contrast,
structural variables (depth, surface area) reliably predict
responses to unfamilar forms. We investigated the hypothesis that
patients with ideomotor apraxia (defective object use and
pantomime, n = 7) due to left parietal damage would be impaired in
producing and recognizing hand postures with both familiar and
unfamiliar forms, indicating deficits in responding to both
functional and structural aspects of objects. We also assessed the
previously reported temporal-lesioned agnosic subject, FB, who
could demonstrate the manipulation of objects he did not recognize.
Apraxics' performance suggested degraded or inaccessible cognitive
representations of hand shape in response to both functional and
structural factors and on both production and recognition tasks. In
one apraxic subject, performance was better with familiar than
unfamiliar forms, suggesting particular deficits in response to
object structure. In contrast, FB responded normally to object
structure, but poorly when structure and function conflicted. We
discuss implications of the data for the roles of temporal and
parietal structures in hand shaping for object use.
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