Intraparietal bimodal neurones delineating extrinsic space through intrinsic actions

Abstract

We can mentally calibrate the directions of our bodily movements into visual coordinate systems to achieve purposeful actions in space. Alternatively, we can apprehend characteristics of the peri-personal space through actions performed by our own body parts. Such interactions between representations of our body motions and extrinsic space should occur in the intraparietal cortices, where the hierarchically processed somatosensory information adjoins the information on spatial vision processed along the dorsal stream. In this brain area of monkeys, we analyzed the response properties of "bimodal joint neurones", which responded simultaneously to forearm joint displacements and visual stimuli moving in one direction in space. For the majority of these neurones, the directions of hand movements in space as a result of adequate joint displacements were congruent with the preferred directions of the moving visual stimuli. When the arm position was rotated, the preferred direction of the joint displacement became inverted so as to match the induced hand movement in space with the preferred visual stimulus direction. On the other hand, in some neurones the visual preferred direction became inverted when the joint was rotated, becoming to match the preferred direction of joint displacement. Hence, intraparietal neurones appear not only to represent mental recalibration of intrinsic movements into extrinsic coordinates, but also render delineation of extrinsic space through intrinsic actions.