Part of Advances in Neural Information Processing Systems 18 (NIPS 2005)
Michele Rucci
Under natural viewing conditions, small movements of the eye and body prevent the maintenance of a steady direction of gaze. It is known that stimuli tend to fade when they are stabilized on the retina for several sec- onds. However, it is unclear whether the physiological self-motion of the retinal image serves a visual purpose during the brief periods of natural visual fixation. This study examines the impact of fixational instability on the statistics of visual input to the retina and on the structure of neural activity in the early visual system. Fixational instability introduces fluc- tuations in the retinal input signals that, in the presence of natural images, lack spatial correlations. These input fluctuations strongly influence neu- ral activity in a model of the LGN. They decorrelate cell responses, even if the contrast sensitivity functions of simulated cells are not perfectly tuned to counter-balance the power-law spectrum of natural images. A decorrelation of neural activity has been proposed to be beneficial for discarding statistical redundancies in the input signals. Fixational insta- bility might, therefore, contribute to establishing efficient representations of natural stimuli.