OBJECT REPRESENTATION IN THE VENTRAL PREMOTOR CORTEX (AREA F5) OF THEMONKEY

Visual and motor properties of single neurons of monkey ventral premot or cortex (area F5) were studied in a behavioral paradigm consisting o f four conditions: object grasping in Light, object grasping in dark, object fixation, and fixation of a spot of light. The employed objects were six different three-dimensional (3-D) geometric solids. Two main types of neurons were distinguished: motor neurons (n = 25) and visuo motor neurons (n = 24). Motor neurons discharged in association with g rasping movements. Most of them (n = 17) discharged selectively during a particular type of grip. Different objects, if grasped in similar w ay, determined similar neuronal motor responses. Visuomotor neurons al so discharged during-active movements, but, in addition, they fired al so in response to the presentation of 3-D objects. The majority of vis uomotor neurons (n = 16) showed selectivity for one or few objects. Th e response was present both in object grasping in light and in object fixation conditions. Visuomotor neurons that selectively discharged to the presentation of a given object discharged also selectively during grasping of that object. In conclusion, object shape is coded in F5 e ven when a response to that object is not required. The possible visua l or motor nature of this object coding is discussed.