The retinotopic match between area 17 and its targets in visual suprasylvian cortex.

It is widely believed that cells in area 17 send axons specifically to neurons in other cortical areas whose receptive fields coincide with their own. We asked whether this was true in cats for area 17's projection to a large suprasylvian visual area, the Clare-Bishop area. Receptive fields were plotted at multiple sites in the Clare-Bishop area. Then, in area 17, anterograde tracer was injected at a retinotopically-characterized site, giving rise to patches of labeled terminals in the Clare-Bishop area. Receptive field centers recorded within these patches were located close to the visual field location at the injection site in area 17. Receptive fields recorded outside of labeled patches, on the other hand, were never in register with that plotted in area 17. However, due to their large size, even fields located outside of labeled patches often encompassed the visual field point injected in area 17. In other experiments, receptive fields for both neurons and presumed cortical afferents were recorded at the same site in the Clare-Bishop area. The centers of such pairs of receptive fields were on average less than 1 degree apart. Finally, the gaps between widely separated patches of label were investigated. Both physiological and anatomical evidence indicated that a different part of the visual field was represented in gaps than in the adjacent patches.