Direction selectivity of simple cells in the primary visual cortex: Comparison of two alternative mathematical models. II: Velocity tuning and response to moving bars

The two models of direction selectivity, presented in a previous paper, are used to investigate the response of simple cells to moving bars with different length, luminance and orientation. Most results agree with experimental data reported in the literature. However, a striking difference between the models is observable after a reduction in bar length. The antiphase model predicts that the optimal direction of movement for a short bar is equal to the optimal direction for a long bar, whereas the in-phase model predicts that the two optimal directions are orthogonal. This difference may allow experimental discrimination between the two models.