Figure 3.

Responses of an MC cell to abrupt displacements of a modulating target on a mean gray and black background. A, Responses of a typical MC On-center cell initially located just outside or just inside the modulation edge to displacement (20 arc min) of a target border over the RF center. The sinusoid shows the modulation phase of the target. Abrupt displacements of 20 arc min in one frame were applied at four phases through the modulation cycle, as indicated in the sketches above the sinusoid (target modulation 0.2 Hz, 40% contrast, mean of 20 responses, bin width 50 ms). Plots of response histograms represent the effects of a rightward displacement that occurs mid-histogram (vertical dotted lines). Top row of histograms, The displacement moved the target over the RF located just outside the modulation edge. Bottom row of histograms, The displacement moved the surround over the RF located just inside the modulation edge, causing a change in the polarity of the response. The horizontal dashed lines indicate the estimated depth of modulation to the stationary target. The phase of the stimulus modulation (0°, 90°, 180°, and 270°) determines the response to the displacement. B, Responses with a dark surround in a similar format. Response amplitude was little affected by the phase of the target modulation or whether modulation was present.