Figure 1.

The stimulus design. a, The stimulus consisted of four sinusoidal grating patches placed in the periphery (6.4°) of the four quadrants. b, Left, The temporal structure of the stimulus in the test blocks. The gray solid and dashed curves depict the time courses of the contrast modulation in the surround in two different phase conditions (phase A: sine [0°]; phase B: negative cosine [−90°]), and the black curve represents the difference of the two phases. The modulation period, T, was either 40 s (subject 2) or 48 s (subjects 1 and 3). Right, Snapshots illustrating the stimulus appearance when the contrast in the surround changed from high (100%) to low (20%). The contrast of the center grating was fixed at 100% in the HCC condition and 20% in the LCC condition.