Functional retinotopy of monkey visual cortex

The operations of primary visual cortex generate continuous representations of orientation, ocular dominance, and retinotopy that, to fit in two dimen sions, organize at separate but overlapping scales (e.g., 20-500 mum, 200 m um to 5 mm, and 2-33 mm). Where their scales overlap, these organizations i nteract; iso-orientation contours cross ocular dominance columns at right a ngles, and ocular dominance columns distort retinotopy near the V1/V2 borde r. To explore these interactions, we developed an optical technique for vis ualizing retinotopy in vivo that allows us to analyze it in relation to ocu lar dominance and orientation patterns. Our results show local retinotopic distortions in every region of macaque V1 that we examine, including region s far from the V1/V2 border. They also show a consistent relation between l ocal axes of distortion and ocular dominance slabs, which they intersect at angles of similar to 90 degrees. A further correlation is provided by reti notopic maps from New World primates that show less distortion (9 vs 60%) i n two species characterized by an absence of pronounced ocular dominance co lumns. Retinotopic maps from these New World primates also revealed an unex pected tilt of the vertical midline representation that diverged from the V 1/V2 border by an angle of similar to 20 degrees. Overall, these results su ggest a general tendency for slab-based organizations to distort retinotopy by representing the same part of space more than once in adjacent slabs.