In our environment, we costantly make goal-oriented hand movements that can be performed in light, as well as in darkness. Area V6A is a visuomotor area of the medial posterior parietal cortex. It contains neurons activated by the execution of reaching movements as well as neurons modulated by passive somatosensory and visual stimulations. In the present work we analyse the effect of visual feedback on reaching activity of V6A neurons.

Three macaques were trained to execute reaching movements towards targets located in different positions in the peripersonal space. Reaches were performed in darkness, where only the reaching target was visible, and in full light, where the monkey also saw its own moving arm and the environment. About 85% of V6A neurons were significantly modulated by the task in at least one of the two backgrounds. The majority of task-related cells (69%) showed reach-related activity in both visual conditions. A small number of cells (15%) were modulated only in light while others (16%) only in dark. The sight of the moving arm often changed dramatically the cell's response to arm movements. In some case, the reaching activity was enhanced and in others was reduced. At population level, reach-related modulations were stronger in light than in dark.

These results indicate that complex, non simply additive, interactions occur in area V6A between visual and motor-related signals when reaching movements are orchestrated.

Eyeshots, Fondazione del Monte, MIUR