Cooperative and temporally structured information in the visual cortex

We have examined the information contained in the coordination of groups of cells in the primary visual cortex of the cat recorded with a 5×5 microelectrode array. When testing small differences (<10°) in stimulus orientation with an information-theoretic distance, response discrimination depended on the temporal resolution of response sampling and improved when including response history. Joint activity also enhanced response discrimination and the enhancement was proportionally larger when more cells were sampled. Spike timing and intervals provided information about fine orientation differences. Even a small rotation of the visual stimulus produced clear time shifts in the response structure with little or no change in the spike count. Larger orientation differences (>10°) are discriminated easily on the basis of the independent spike counts. We conclude that synchrony provides a reliable mechanism to transmit fine structure of visual information and offers an efficient cooperative neural code that we have only begun to explore.