Psychophysical Tests of the Hypothesis of a Bottom-Up Saliency Map in Primary Visual Cortex
Figure 5
Demonstration and Testing the Predictions on Spatial Grouping
(A–G) Portions of different stimulus patterns used in the segmentation experiments. Each row starts with an original stimulus (left) without task-irrelevant bars, followed by stimuli when various task-irrelevant bars are superposed on the original.
(H) RT data when different stimulus conditions are randomly interleaved in experimental sessions. The un-normalized mean RT for four subjects (AP, FE, LZ, NG) in condition (A) are: 493, 465, 363, 351 ms. For each subject, it is statistically significant that RTC > RTA (p < 0.0005), RTD > RTB (p < 0.02), RTA > RTB (p < 0.05), RTA < RTE, RTG (p < 0.0005), RTD > RTF, RTC > RTE, RTG (p < 0.02). In three out of four subjects, RTE < RTG (p < 0.01), and in two out of four subjects, RTB < RTF (p < 0.0005). Meanwhile, by matched sample t-tests across subjects, the mean RT values between any two conditions are significantly different (p smaller than values ranging from 0.0001 to 0.04).
(I) Schematics of responses from relevant (red) and irrelevant (blue) neurons, with (solid curves) and without (dot-dashed curves) considering general suppressions, for situations in (E–G). Interference from the irrelevant features arises from the spatial peaks in their responses away from the texture border.