Organization of intracortical circuits in relation to direction preferencemaps in ferret visual cortex

Neurons in the primary visual cortex are selective for the direction of mov ement of a visual stimulus. Like other stimulus features, direction prefere nce is mapped on the cortical surface in a systematic manner. Intracortical synaptic circuits, in particular inhibitory connections, have been implica ted in the emergence of direction selectivity. Whether intracortical inhibi tion specifically suppresses responses to the nonpreferred direction or has a nonspecific "thresholding" effect is still controversial. To address the se questions we investigated the relationship between patterns of intracort ical synaptic connections and direction domains in ferret primary visual co rtex (area 17) using a combined in vivo-in vitro approach. Excitatory synap tic inputs were iso-direction-tuned. The majority of local inhibitory input s were also iso-direction-tuned. However, similar to 40% of inhibitory conn ections originated in regions preferring the opposite direction. These find ings indicate that specific inhibitory interactions between cortical region s of opposite direction preference may contribute to the emergence and shar pening of direction selectivity.