COMMON REFERENCE FRAME FOR NEURAL CODING OF TRANSLATIONAL AND ROTATIONAL OPTIC FLOW

Self-movement of an organism through the environment is guided jointly by information provided by the vestibular system and by visual pathwa ys that are specialized for detecting 'optic flow'(1,2). Motion of any object through space, including the self-motion of organisms, can be described with reference to six degrees of freedom: rotation about thr ee orthogonal axes, and translation along these axes, Here we describe neurons in the pigeon brain that respond best to optic flow resulting from translation along one of the three orthogonal axes, We show that these translational optic flow neurons, like rotational optic flow ne uron(3-5), share a common spatial frame of reference with the semicirc ular canals of the vestibular system. The three axes to which these ne urons respond best are the vertical axis and two horizontal axes orien tated at 45 degrees to either side of the body midline.