Article

Apraxia after left inferior parietal lesions has been widely interpreted as
evidence of damage or impaired access to representations of tool-use, but most
research has investigated pantomime of tool actions, not handling of actual
tools. An alternative account is that inferior parietal damage does not affect
tool-use representations but impairs cognitive processing about postural and
hand-tool spatial relationships which is necessary for planning and controlling
any complex action. Four apraxic patients and 10 age-matched controls were asked
to reach rapidly for tools or abstract objects of similar dimensions. Under
conditions of time pressure and divided attention, the patients frequently failed
to invert the hand to grasp inverted tools by the handle, whereas ability to
invert the hand to avoid a barrier and grasp abstract objects was largely
unimpaired. Frequency of errors in tool grasping correlated with severity of
apraxia. When inverted tools were correctly grasped, rotation of the wrist
occurred later during the reaching movement than when inverting the hand to grasp
an abstract object. These data are consistent with the theory of degraded access
to tool-use representations in apraxia, but this theory cannot account for
co-occurring deficits in imitating or matching meaningless hand or body postures.
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Langue : ANGLAIS