Plasticity in the Structure of Visual Space

Abstract Visual space embodies all visual experiences, yet what determines the topographical structure of visual space remains unclear. Here we test a novel theoretical framework that proposes intrinsic lateral connections in visual cortex as the mechanism underlying the structure of visual space. The framework suggests that the strength of lateral connections between neurons in visual cortex shapes the experience of spatial relatedness between locations in visual field. As such, an increase in lateral connection strength shall lead to an increase in perceived relatedness and a contraction in perceived distance. To test this framework through human psychophysics experiments, we employed a Hebbian training protocol where two point stimuli were flashed in synchrony at separate locations in visual field, to strengthen the lateral connections between two separate groups of neurons in visual cortex. After training, participants experienced a contraction in perceived distance. Intriguingly, the perceptual contraction occurred not only between the two training locations that were linked directly by the changed connections, but also between the outward untrained locations that were linked indirectly through the changed connections. Moreover, the effect of training greatly decreased, if the two training locations were too close together, or too far apart and went beyond the extent of lateral connections. These findings suggest that a local change in the strength of lateral connections is sufficient to alter the topographical structure of visual space. Significance Statement Given that visual space underlies visual perception, it is easy to take its topographical structure for granted. Indeed, most studies focus on object or feature perception that happens within visual space, without first considering the structure of visual space itself. Here we studied plasticity in the structure of visual space. We found that a local strengthening of lateral connections between retinotopically-tuned visual cortical neurons, induced by synchronized, repetitive presentation of two point stimuli, could lead to a contraction in perceived distance and a change in visual space structure. We propose lateral connections in visual cortex as the mechanism that relates locations perceptually and shapes the structure of visual space.