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Inferior parietal lobule; premotor cortex; tactile information; visual information
Abstract:
The purpose of this study was to determine the functional organization of the human brain involved in cross-modal discrimination
between tactile and visual information. Regional cerebral blood Øow was measured by positron emission tomography in nine
right-handed volunteers during four discrimination tasks; tactile±tactile (TT), tactile±visual (TV), visual±tactile (VT), and
visual±visual (VV). The subjects were asked either to look at digital cylinders of different diameters or to grasp the digital
cylinders with the thumb and index Ænger of the right hand using haptic interfaces. Compared with the motor control task in which
the subjects looked at and grasped cylinders of the same diameter, the right lateral prefrontal cortex and the right inferior parietal
lobule were activated in all the four discrimination tasks. In addition, the dorsal premotor cortex, the ventral premotor cortex, and
the inferior temporal cortex of the right hemisphere were activated during VT but not during TV. Our results suggest that the
human brain mechanisms underlying cross-modal discrimination have two different pathways depending on the temporal order in
which stimuli are presented.
