Abstract
Like other sensory cortices, the surface area of human primary visual cortex (V1) varies substantially between individuals for reasons that are unknown. Such variability is typically ignored by the vast majority of studies focusing only on commonalities in perception and visual processing. Here, we instead used functional MRI and standard retinotopic mapping procedures to show that differences in the surface area of human V1 were negatively correlated with the magnitude of a number of common visual illusions: the Ebbinghaus and Ponzo illusions, where two objects that are physically identical are made to appear different in size due to their context. We further showed that this correlation was also present for the tilt illusion, where the orientation of a central grating appears to be rotated due to the orientation of the surround. Importantly, all of these effects were specific to V1, as the surface area higher extrastriate regions did not show significant correlations. Because such illusions dissociate changes in conscious perception from differences in physical stimulation, our findings indicate not only that visual perception varies substantially across individuals, but also that the surface area of V1 is a neural correlate of differences in the contents of consciousness. Finally, we showed that V1 surface area also strongly correlated with sensitivity for orientation, but not contrast, discrimination. Taken together, our findings reveal a link between our subjective perceptual experience of the visual environment and the functional architecture of the visual cortex.