Transient spatiotopic integration across saccadic eye movements mediates visual stability,J Neurophysiol, 4 (109), 1117-1125.

Eye movements pose major problems to the visual system, because each new saccade changes the mapping of external objects on the retina. It is known that stimuli briefly presented around the time of saccades are systematically mislocalized, whereas continuously visible objects are perceived as spatially stable even when they undergo large transsaccadic displacements. In this study we investigated the relationship between these two phenomena and measured how human subjects perceive the position of pairs of bars briefly displayed around the time of large horizontal saccades. We show that they interact strongly, with the perisaccadic bar being drawn toward the other, dramatically altering the pattern of perisaccadic mislocalization. The interaction field extends over a wide range (200 ms and 20 degrees ) and is oriented along the retinotopic trajectory of the saccade-induced motion, suggesting a mechanism that integrates pre- and postsaccadic stimuli at different retinal locations but similar external positions. We show how transient changes in spatial integration mechanisms, which are consistent with the present psychophysical results and with the properties of “remapping cells” reported in the literature, can create transient craniotopy by merging the distinct retinal images of the pre- and postsaccadic fixations to signal a single stable object.

Long-term effects of monocular deprivation revealed with binocular rivalry gratings modulated in luminance and in color,J Vis, 6 (13),

During development, within a specific temporal window called the critical period, the mammalian visual cortex is highly plastic and literally shaped by visual experience; to what extent this extraordinary plasticity is retained in the adult brain is still a debated issue. We tested the residual plastic potential of the adult visual cortex for both achromatic and chromatic vision by measuring binocular rivalry in adult humans following 150 minutes of monocular patching. Paradoxically, monocular deprivation resulted in lengthening of the mean phase duration of both luminance-modulated and equiluminant stimuli for the deprived eye and complementary shortening of nondeprived phase durations, suggesting an initial homeostatic compensation for the lack of information following monocular deprivation. When equiluminant gratings were tested, the effect was measurable for at least 180 minutes after reexposure to binocular vision, compared with 90 minutes for achromatic gratings. Our results suggest that chromatic vision shows a high degree of plasticity, retaining the effect for a duration (180 minutes) longer than that of the deprivation period (150 minutes) and twice as long as that found with achromatic gratings. The results are in line with evidence showing a higher vulnerability of the P pathway to the effects of visual deprivation during development and a slower development of chromatic vision in humans.

Early interaction between vision and touch during binocular rivalry,Multisens Res, 3 (26), 291-306.

Multisensory integration is known to occur at high neural levels, but there is also growing evidence that cross-modal signals can be integrated at the first stages of sensory processing. We investigated whether touch specifically affected vision during binocular rivalry, a particular type of visual bistability that engages neural competition in early visual cortices. We found that tactile signals interact with visual signals outside of awareness, when the visual stimulus congruent with the tactile one is perceptually suppressed during binocular rivalry and when the interaction is strictly tuned for matched visuo-tactile spatial frequencies. We also found that voluntary action does not play a leading role in mediating the effect, since the interaction was observed also when tactile stimulation was passively delivered to the finger. However, simultaneous presentation of visual and tactile stimuli is necessary to elicit the interaction, and an asynchronous priming touch stimulus is not affecting the onset of rivalry. These results point to a very early cross-modal interaction site, probably V1. By showing that spatial proximity between visual and tactile stimuli is a necessary condition for the interaction, we also suggest that the two sensory spatial maps are aligned according to retinotopic coordinates, corroborating the hypothesis of a very early interaction between visual and tactile signals during binocular rivalry.

Spatiotemporal filtering and motion illusions, Journal of Vision, (13)10-21.

Our group has long championed the idea that perceptual processing of information can be anchored in a dynamic coordinate system that need not correspond to the instantaneous retinal representation that need not correspond to the istantaneus retinal representation…