Object affordance modulates visual responses in the macaque medial posterior parietal cortex.

Area V6A is a visuomotor area of the dorsomedial visual stream that contains cells modulated by object observation and by grip formation. As different objects have different shapes but also evoke different grips, the response selectivity during object presentation could reflect either the coding of object geometry or object affordances. To clarify this point, we here investigate neural responses of V6A cells when monkeys observed two objects with similar visual features but different contextual information, such as the evoked grip type. We demonstrate that many V6A cells respond to the visual presentation of objects and about 30% of them by the object affordance. Given that area V6A is an early stage in the visuomotor processes underlying grasping, these data suggest that V6A may participate in the computation of object affordances. These results add some elements in the recent literature about the role of the dorsal visual stream areas in object representation and contribute in elucidating the neural correlates of the extraction of action-relevant information from general object properties, in agreement with recent neuroimaging studies on humans showing that vision of graspable objects activates action coding in the dorsomedial visual steam.