VISUAL PATHWAYS FOR OBJECT-ORIENTED ACTION AND OBJECT RECOGNITION - FUNCTIONAL-ANATOMY WITH PET

The purpose of this study was to identify the functional anatomy of th e mechanisms involved in visually guided prehension and in object reco gnition in humans. The cerebral blood flow of seven subjects was inves tigated by positron emission tomography Three conditions were performe d using the same set of stimuli. in the 'grasping' condition, subjects were instructed to accurately grasp the objects. In the 'matching' co ndition, subjects were requested to compare the shape of the presented abject with that of the previous one. In the 'pointing' condition (co ntrol), subjects pointed towards the objects. The comparison between g rasping and pointing showed a regional cerebral blood flow (rCBF) incr ease in the anterior part of the inferior parietal cortex and part of the posterior parietal cortex. The comparison between grasping and mat ching showed an rCBF increase in the cerebellum the left frontal corte x around the central sulcus, the mesial frontal cortex and the left in ferior parietal cortex. Finally, the comparison between matching and p ointing showed an rCBF increase in the right temporal cortex and the r ight posterior parietal cortex. Thus object-oriented action and object recognition activate a common posterior parietal area, suggesting tha t some kind of within-object spatial analysis was processed by this ar ea whatever the goal of the task.