Visual Feedback from the Own Acting Hand Modulates the Activity of Grasping Neurons in Monkey Premotor Area F 5

Visual responses in the monkey ventral premotor cortex have been explored since long time. Area F5 has been shown to contain grasping neurons that visually discharge either to 3D-object presentation (canonical neurons) or to the observation of actions performed by other individuals (mirror neurons). It has been suggested that the mirror response results from the progressive generalization to others’ actions of a visuomotor link which, during action execution, associates the vision of the own acting effector with the motor program selected for the ongoing action. To start tackling this hypothesis, we specifically asked whether area F5 contains neurons responding to the observation of one’s own grasping movement. A specially-designed experimental apparatus was used to test F5 neuronal discharge while monkeys were engaged in a reach-to-grasp task and either continuous or transient visual information on the ongoing movement was made available. Singleunit activity was additionally recorded from the hand region of the primary motor cortex (area F1). Neuronal responses evoked by the vision of the own entire grasping action or of brief meaningful phases of it were detected in both areas. However, F5 modulation was overall more strong and specific. The finding that neurons in area F5 exhibit discharge properties that are common to both purely motor and mirror neurons allows the formulation of important assumptions about the critical role of online visual information during grasping and the nature of the mirror discharge.