Neural Basis of Object-Centered Representations

Abstract

We present a neural model that can perform eye movements to a particular side of an object regardless of the position and orienta(cid:173) tion of the object in space, a generalization of a task which has been recently used by Olson and Gettner [4] to investigate the neu(cid:173) ral structure of object-centered representations. Our model uses an intermediate representation in which units have oculocentric recep(cid:173) tive fields- just like collicular neurons- whose gain is modulated by the side of the object to which the movement is directed, as well as the orientation of the object. We show that these gain modulations are consistent with Olson and Gettner's single cell recordings in the supplementary eye field. This demonstrates that it is possible to perform an object-centered task without a representation involv(cid:173) ing an object-centered map, viz., without neurons whose receptive fields are defined in object-centered coordinates. We also show that the same approach can account for object-centered neglect, a situ(cid:173) ation in which patients with a right parietal lesion neglect the left side of objects regardless of the orientation of the objects.