Figure 1.

Experimental setup. (A) The insert shows the orientation of ferret brain. The visual cortex is enlarged at the left. The hexagonal photodiode array monitor visual areas 17, 18, 19, and 21. Each channel of the array picks up the signal from a cortical area with a diameter of approximately 150 μm. The representations of the vertical meridians of the field of view are red, the horizontal meridian is green and the representation of the 5° center of field of view, yellow (after Manger et al. 2002). In all experiments 2 × 2° white squares were presented for 83 ms along the vertical meridian. The baseline condition was a homogenous gray background of the same average luminance as the stimulus conditions. (B) Experiment 1, 1 square appears 1st 3.5° below, then at 83 ms at the center of field of view, and at 166 ms 3.5° above the horizontal meridian. Control stimuli: a single stationary square displayed in 1 of these 3 positions. (C) Experiment 2: As in (B) but the onset times are 0, 42, and 83 ms. (D) Experiment 3: onset times 0 and 83 ms, distance 7° between 1st and last square. (E) Experiment 4: split motion, central square presented at 0 ms, at 83 ms 1 square in top + 3.5° and 1 in lower position −3.5° from the central square. Controls (not shown) at 0 ms single square in central position, at 83 ms the top and lower square simultaneously.