The Space Around Us

摘要

Space, although unitary when examined in-trospectively, is not represented in the brain as a single multipurpose map. On the contrary, in the brain there-are numerous spatial maps (1 -3). Of. these, many are located in cortical areas that participatein the control of movement, such as eye movements, head movements, arm movements, and so on. The map located in the ventral premotor cortex (area F4) is paradigmatic among the spatial maps related to skeletal movements. In this area, most neurons discharge in association with movements of the head or the arm (4). Furthermore, a large pro-portion of them are bimodal, responding both to visual three-dimensional stimuli and totac tile stimuli, mostly applied to the face or arm. A surprising property of F4neurons is that theii: visual receptive fields (RFs) are circumscribed to the space around the' tactile RFs, as if the cutaneous space extended into the Visual space adjacent to it (peripersonal space) (4--9). Another surprising property is that visual RFs of F4 neurons remain anchored to the body regardless of the position of the eyes and of the body parts on which the tactile RF is located (7-11) (see figure).