Nitric oxide and the development of long-range horizontal connectivity

We analyse the role of a slowly decaying, rapidly diffusing messenger (Nitric Oxide) in the development of horizontal connectivity. We show that the connectivity develops to represent temporal correlations in the stimulus set. We apply this model to the development of long-range horizontal connections in primary visual cortex. Simulations show that long-range horizontal axons will connect neurons with similar orientation selectivity, as is observed in animal experiments. The model's predictions are testable by rearing animals in visual environments with controlled temporal correlations or by intervening in the process that generates the diffusing messenger.