We discussed a recent paper that uses ocular following responses in humans to demonstrate a dissociation between the oculomotor system and the perceptual system. Using stimuli generated by filtering noise in the Fourier domain the authors could construct naturalistic random-phase textures that have identical speeds, but differ in their frequency content. Interestingly, as the stimuli became more broadband, the oculomotor system could take advantage of the richness of the stimulus and became more rapid and precise whereas the humans’ psychophysical performance decreased.
Rather than conclude that there are two distinct visual systems, the authors hypothesize that both the oculomotor and perceptual systems rely on the same encoding and decoding mechanism and instead have different gain control . Using likelihood base methods with an added gain control step, they fit the dissociated response of the two systems by using Naka-Rushton gain control for the eye movements and everybody’s friend, divisive normalization, for the perceptual system.
- Claudio Simoncini, Laurent U. Perrinet, Anna Montagnini, Pascal Mamassian, Guillaume S. Masson. More is not always better: dissociation between perception and action explained by adaptive gain control