MOTION ANISOTROPIES AND HEADING DETECTION

In motion-processing areas of the visual cortex in cats and monkeys, a n anisotropic distribution of direction selectivities displays a prefe rence for movements away from the fovea. This 'centrifugal bias' has b een hypothetically linked to the processing of optic flow fields gener ated during forward locomotion. In this paper, we show that flow field s induced on the retina in many natural situations of locomotion of hi gher mammals are indeed qualitatively centrifugal in structure, even w hen biologically plausible eye movements to stabilize gaze on environm ental targets are performed. We propose a network model of heading det ection that carries an anisotropy similar to the one found in cat and monkey. In simulations, this model reproduces a number of psychophysic al results of human heading detection. It suggests that a recently rep orted human disability to correctly identify the direction of heading from optic flow when a certain type of eye movement is simulated might be linked to the noncentrifugal structure of the resulting retinal fl ow field and to the neurophysiological anisotropies.