Abstract
The population coding here involves pooling the activities of neurons based on single unit recordings. We are interested in the neuronal mechanism of short-latency vergence eye movements elicited by disparity steps of a large-field random-dot pattern. We simultaneously recorded vergence eye movements and single unit activities in the medial superior temporal (MST) area of monkeys by applying 11 disparity steps. Disparity tuning curves, describing the dependence of the responses on the magnitude of the steps, were calculated both for neuronal and ocular responses, i.e. vergences. Very few MST neurons had disparity tuning curves resembling those of the vergence responses. Yet, when the curves for all the cells recorded from a given monkey were simply summed together they fitted the tuning curves for the vergence responses of the monkey very closely, even reproducing the idiosyncratic differences between the animals. The results suggest that the initial vergence responses associated with disparity steps applied to the large-field patterns are encoded in the summed activity of the disparity-sensitive cells in the MST. Further, the latency data indicate that these neuronal activities in the MST occur early enough to play a role in the generation of the vergence eye movements at short latencies. [Jpn J Physiol 54 Suppl:S34 (2004)]
