The distribution of cerebral activity related to visuomotor coordination indicating perceptual and executional specialization

The distribution of increased regional cerebral blood flow (rCBF) related t o visuomotor coordination was studied by means of positron emission tomogra phy (PET) in normal subjects. An experimental condition, in which a vertica lly presented zigzag figure had to be copied in a horizontal orientation, w as compared with a control condition in which the same horizontal drawing w as made, guided by a horizontally presented example. Cognitive components d ealing with the mismatch in visual orientation resulted in activation of (i ) right dorsal premotor cortex, (ii) right posterior parietal cortex, (iii) visual cortex (area V1) and (iv) left fusiform gyrus. In a second experime nt, conditions were compared in which the same horizontal zigzag figure was copied in either a vertical or a horizontal orientation. Now, the motor co mponents of the transformation of orientation appeared to be associated onl y with left premotor cortex activation. The differential distribution of ac tivations is regarded to reflect the selective effort to cope with either t he visual or the motor component of spatial incongruity, and indicates spec ialization for perceptual and executive components in visuomotor control. W e propose that the perceptual component of visuomotor transformation in our experiment relates to a realignment of the coordinates of a percept to an internally defined coordinate system. The executive component relates to gu idance of movement within an internal representation of space. In a precedi ng behavioural experiment, a majority of patients with Parkinson's disease (PD) failed on the task in which they had to make a horizontal copy of a ve rtically presented picture. This finding may suggest a deficit in the maint enance of an internal spatial representation to guide movement. (C) 1999 El sevier Science B.V. All rights reserved.