Early coding of visuomanual coordination during reaching in parietal area PEc

The parietal mechanisms of eye-hand coordination during reaching were studi ed by recording neural activity in area PEc while monkeys performed differe nt tasks, aimed at assessing the influence of retinal, hand-, and eye-relat ed signals on neural activity. The tasks used consisted of 1) reaching to f oveated and 2) to extra-foveal targets, with constant eye position; and 3) saccadic eye movement toward, and holding of eye position on peripheral tar gets, the same as those of the reaching tasks. In all tasks, hand and/or ey e movements were made from a central position to eight peripheral targets. A conventional visual fixation paradigm was used as a control task, to asse ss location and extent of visual receptive field of neurons. A large propor tion of cells in area PEc displayed significant relationships to hand movem ent direction and position. Many of them were also related to the eye's pos ition. Relationships to saccadic eye movements were found for a smaller pro portion of cells. Most neurons were tuned to different combination of hand- and eye-related signals; some of them were also influenced by visual infor mation. This combination of signals can be an expression of the early stage s of the composition of motor commands for different forms of visuomotor co ordination that depend on the integration of hand- and eye-related informat ion. These results assign to area PEc, classically considered as a somatose nsory association cortex, a new visuomotor role.