Visual field biases for near and far stimuli in disparity selective columns in human visual cortex

To test for underlying brain mechanisms, we presented visual stimuli at different perceptual distances, while measuring high-resolution fMRI in human subjects. First, we localized disparity-selective thick stripes and thick-type columns in secondary and third visual cortical areas, respectively. Consistent with the perceptual bias, we found that the thick stripe/columns that represent the lower visual field also responded more selectively to near rather than far visual stimuli. Conversely, thick stripe/columns that represent the upper visual field show a complementary bias, i.e. selectively higher activity to far rather than near stimuli. Thus, the statistics of natural scenes may play a significant role in the organization of near- and far-selective neurons within V2 thick stripes and V3 thick-type columns.