Functional connectivity of disparity-tuned neurons in the visual cortex

Different mechanisms have been proposed concerning how disparity-tuned neurons might be connected to produce the signals for depth perception. Here we present neurophysiological evidence providing insight on this issue. We have recorded simultaneously from pairs of disparity-tuned neurons in the cat's striate cortex. The purpose was to determine the relationships between disparity tuning and functional connectivity revealed through neural cross-correlograms. Monosynaptic connections tend to be stronger between pairs of cells with similar disparity tuning. Pairs of complex cells tend to have either similar tuning or nearly opposite tuning with an absence of quadrature relations. Pairs with at least one simple cell do have some nearly quadrature relationships when they are recorded from the same electrode. Coarse-to-fine connections (i.e., the presynaptic cell has lower disparity frequency and larger disparity range) tend to be stronger but less frequent than those of a fine-to-coarse nature. Our results are consistent with a system that produces weighted averaging across cells that are tuned to similar disparities but different disparity scales to reduce false matches.