Is direction selectivity of cat area 17 cells always independent of contrast and dependent on short-distance interactions?

Summary In a study of area 17 of the paralysed and anesthetized cat it was found that for a small sub-group of cells with peripherally located receptive fields (11/123), the direction selectivity was critically dependent on the use of high contrast stimulation. By covering parts of the receptive field with a mask, it was found that in some cells the suppression of responses to movement in the non-preferred direction was due to the presence of a suppressive area located just outside the discharge region. Direction selective suppression was present only when a high contrast bar (light or dark) crossed this area before entering the discharge region.