Functional properties of grasping-related neurons in the ventral premotor area F5 of the macaque monkey.

We investigated the motor and visual properties of F5 grasping neurons, using a controlled paradigm that allows the study of the neuronal discharge during both observation and grasping of many different three-dimensional objects with and without visual guidance. All neurons displayed a preference for grasping of an object or a set of objects. The same preference was maintained when grasping was performed in the dark without visual feedback. In addition to the motor-related discharge, about half of the neurons also responded to the presentation of an object or a set of objects, even when a grasping movement was not required. Often the object evoking the strongest activity during grasping also evoked optimal activity during its visual presentation. Hierarchical cluster analysis indicated that the selectivity of both the motor and the visual discharge of the F5 neurons is determined not by the object shape but by the grip posture used to grasp the object. Because the same paradigm has been used to study the properties of hand-grasping neurons in the dorsal premotor area F2, and in the anterior intraparietal area (AIP), a comparison of the functional properties of grasping-related neurons in the three cortical areas (F5, F2, AIP) is addressed for the first time.