The functional role of serial dependence, Proceedings of the Royal Society of London B.

The world tends to be stable from moment to moment, leading to strong serial correlations in natural scenes. As similar stimuli usually require similar behavioral responses, it is highly likely that the brain has developed strategies to leverage these regularities. A good deal of recent psychophysical evidence is beginning to show that the brain is sensitive to serial correlations, causing strong drifts in observer responses towards previously seen stimuli. However, it is still not clear that this tendency leads to a functional advantage. Here we test a formal model of optimal serial dependence and show that as predicted, serial dependence in an orientation reproduction task is dependent on current stimulus reliability, with less precise stimuli, such as low spatial frequency oblique Gabors, exhibiting the strongest effects. We also show that serial dependence depends on the similarity between two successive stimuli, again consistent with behavior of an ideal observer aiming at minimizing reproduction errors. Lastly, we show that serial dependence leads to faster response times, indicating that the benefits of serial integration go beyond reproduction error. Overall our data show that serial dependence has a beneficial role at various levels of perception, consistent with the idea that the brain exploits temporal redundancy of the visual scene as an optimization strategy

Cortical BOLD responses to moderate- and high-speed motion in the human visual cortex, Sci Rep, 1 (8), 8357.

We investigated the BOLD response of visual cortical and sub-cortical regions to fast drifting motion presented over wide fields, including the far periphery. Stimuli were sinusoidal gratings of 50% contrast moving at moderate and very high speeds (38 and 570 °/s), projected to a large field of view (~60°). Both stimuli generated strong and balanced responses in the lateral geniculate nucleus and the superior colliculus. In visual cortical areas, responses were evaluated at three different eccentricities: central 0-15°; peripheral 20-30°; and extreme peripheral 30-60°. “Ventral stream” areas (V2, V3, V4) preferred moderate-speeds in the central visual field, while motion area MT+ responded equally well to both speeds at all eccentricities. In all other areas and eccentricities BOLD responses were significant and equally strong for both types of moving stimuli. Support vector machine showed that the direction of the fast-speed motion could be successfully decoded from the BOLD response in all visual areas, suggesting that responses are mediated by motion mechanisms rather than being an unspecific preference for fast rate of flicker. The results show that the visual cortex responds to very fast motion, at speeds generated when we move our eyes rapidly, or when moving objects pass by closely.