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Abstract:
Abstract: Has the human brain evolved specialized mechanisms
to deal with the problem of planning tool prehension apart from
those dedicated to hand movements? To the extent that specialized
mechanisms exist for planning tool use, we expected involvement of
regions beyond those contralaterally-organized motor areas known to
be active when planning and controlling of hand movements. We used
event-related fMRI to explore two planning processes fundamental to
tool prehension: hand preparation and grip selection. Eight
right-handed subjects viewed images of dowels presented in a
variety of different three-dimensional orientations and judged
which end their thumb would be on if they adopted the most
comfortable power grip with the visually precued hand (e.g.,
Johnson, 1998, 1999). No actual hand movements were made. During
task performance we acquired 16 8mm slices covering the whole head
(TR 2 sec, TE 40ms, 148 consecutive vols per run). Data analysis
followed procedures described in Rotte, et al., 1999. In contrast
to hand movements, planning tool prehension involved nearly
identical areas regardless of whether judgments were based on the
left or right hands. Further, hand preparation and grip selection
components seem to be accomplished by partially distinct subsystems
that involved a variety of motor and somatosensory structures as
well as high-level visual processing in the parietal and temporal
lobes.
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