Figure 4.

Responses of a PC cell to abrupt displacements of a modulating target on a mean gray and green background. A, Responses of a +L−M cell to displacement (20 arc min) of a target border over the RF center, with a similar format as in Figure 3, except that chromatic modulation was used. Top row of histograms, The displacement moved the target over the RF located just outside the modulation edge, at the instant indicated by the vertical dashed lines. 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. Displacement responses are superimposed on the ongoing response to the target, depending on the location of the RF and the phase of the displacement. Again, the horizontal dashed lines indicate the estimated depth of modulation to the stationary target, which was greater for PC cells and chromatic modulation than for MC cells and luminance modulation. The phase of the stimulus modulation (0°, 90°, 180°, and 270°) determines the response to the displacement. B, Responses with a green surround in a similar format. Response amplitude was little affected by the phase of the target modulation or whether modulation was present.