Figure 4.

Temporal dynamics distinguish two regions of the visual Wulst. A, Input region response to different stimulus duration. The inset shows an example of the pixels belonging to the central input region in one subject. Relative VSD reflectance (ΔF/F) averaged over input area and stimulus conditions is shown as a mean across experiments (after normalization to the maximum). Response to the gratings moving for 400 ms is shown in blue, and the 800 ms stimulation is drawn in red. For comparison, one of the two responses to a gray screen is shown (in black). The shaded areas depict SD of normalized ΔF/F values evaluated across animals (N = 9 for 400 ms stimulation; N = 5 for 800 ms; and N = 9 + 5 for the blanks). The black bars show the time period in which the two stimuli evoked a significantly different response (unpaired t test, p < 0.05). B, Time course of activity recorded with electrophysiology. Similar analysis was applied to electrode recordings, in which 5 ms binned frequency responses were averaged across all available cells in all subjects, and normalized to the maximum (in contrast to A, no blank subtraction was performed and the mean of prestimulus activity preceding the stimulus onset was subtracted, and not divided). The shaded region depicts SD across experiments (N = 12 for 400 ms, N = 11 for 800 ms stimulation). For each animal, data from 1 to 18 cells was available (in overall, 53 cells for 400 ms, and 77 cells for 800 ms stimulation). Initial activity peaks at ∼50 ms, followed immediately by biphasic decay, first a fast decrease to a stable activity level and dropping slightly below the baseline after the stimulus offset. C, Two-dimensional map from one pigeon presenting the difference in offset latency recorded in 800 and 400 ms stimulation paradigms. Offset was defined as a time at which significance of a given pixel response (averaged across stimulus orientations) dropped below 1, p < 0.99 (for single-condition contours, see Fig. 2).