Abstract
A recent study found that the surface area of primary visual cortex (V1) of healthy adults correlates with the magnitude of the Ebbinghaus illusion, such that individuals with larger V1 have a smaller illusion effect. Since the illusory effect in visual context illusions is based on contextual modulation by adjacent or surrounding stimuli, these results were presumed to be due to differences in neuronal lateral connections between small and large visual cortices (Schwarzkopf, Song, & Rees, 2011). Here we sought to investigate whether visual illusion magnitude correlates with spatial vision (lateral masking and crowding) and whether a perceptual training that is known to modulate lateral masking and crowding will lead to a change in perception of the illusions. We measured the illusion magnitudes of three visual context illusions, the Ebbinghaus, the tilt, and the orientation-dependent contrast illusion, before and after two months of perceptual training in a group of 14 young healthy adults. The perceptual training consisted of detecting Gabor stimuli in the presence of lateral masks and has been shown to reduce spatial and temporal masking (Polat et al., ECVP 2013). It was carried out on iDevices at a distance of 40 cm (GlassesOff application). Before the training, illusion magnitudes of the Ebbinghaus and the tilt illusion significantly correlated with the strength of lateral masking and crowding, which are assumed to rely on lateral interactions. After training we found a reduction in all three illusion measurements indicating a diminished influence of the surround on the perception of the center. We conclude that a reduction of lateral inhibition through perceptual learning leads to a more veridical â€" i.e., less illusory â€" impression of the visual world.
Meeting abstract presented at VSS 2014