Figure 1.

Alternative hypotheses for connectivity at/near the HM representation of area V2. Left panels in (a–c): diagrams of the central 8° of the right visual hemifield. Here and in all remaining figures, the star marks the location of the fovea, (+) (−) indicate the upper and lower visual quadrants, respectively, the dashed horizontal line is the HM, the solid vertical line is the VM, the dotted contours are the iso-eccentricity lines whose eccentricity is indicated. Right panels in (a–c): representations of the right upper and lower visual quadrants onto an outline of unfolded and flattened marmoset striate (V1) and extrastriate cortex (V2 and areas rostral to it). The locations of the ±4° and ±8° eccentricity lines (dotted contours) are shown in V2 (modified from Rosa et al. 2005). For sake of illustration, here and in all remaining figures, the flattened right and left hemispheres are both oriented with the posterior pole on the left. The thick dashed contours and solid contours indicate the location of the HM and VM representations, respectively, the star is the representation of the fovea, (+) (−) are the representation of the upper and lower visual quadrants, respectively, the thin dashed outline is the outline of the dorso-lateral surface of visual cortex prior to unfolding, and the thin solid outline is the outline of unfolded medial and ventral cortex. The light gray area rostral to V2d marked as “DM+?” indicates the location of the upper quadrant representation of area DM according to Rosa et al. (2005). This is a region where the existence of an upper or lower visual field representation is still being debated as detailed in Supplementary Figure 1 (Lyon and Kaas 2001; Rosa et al. 2005). (a) Cells with RFs located at/near the rostral V2d border do not make connections with cortical regions in ventral cortex representing the upper visual field. These cells only make local connections (dark gray oval) and long-range intra-areal connections (light gray oval) within V2d, representing the lower visual field. They also make reciprocal connections only with retinotopically matching regions in the lower visual field representation of other cortical areas (black ovals in V1 and MT). The visual field map of these local and horizontal V2 connections is shown on the right visual hemifield (left panel) as half-ovals of matching shades of gray. (b) V2 cells near the rostral V2d border make local connections with visuotopically neighboring cells in the lower and upper visual quadrants, but long-range connections only with regions of lower visual field representation. The visual field map to the left shows retinotopic continuity of the local connections but not of horizontal connections. (c) V2 cells near the rostral V2d border make local and long-range connections with visuotopically matched and mismatched regions in dorsal and ventral cortex. The visual field map to the left shows retinotopic continuity of both local and horizontal connections.