Fig. 5.

A: best fitting half-Gaussian to the data from a single subject (AA), collapsed across correct and incorrect trials (see methods). B: estimated shape of the half-Gaussian in the same subject on correct (black) and incorrect (blue) trials in voxels tuned 36° away from the target. The additive baseline offset was removed from each curve, and the amplitudes of the black and blue curves were scaled by the observed difference in the response amplitude of voxels tuned 36° from the target on correct and incorrect trials, respectively. C: the squared slope divided by the within-subject trial-by-trial variance for each of the curves shown in B. Solid vertical lines indicate the sample orientation, and the vertical dashed lines indicate where the slope²/variance function peaks (8° from the sample in this subject. Note that because these values are based on voxels tuned to ±36° from sample, the predicted “optimal” off-channel gain would be at 0°). D: same conventions as in B and C but averaged across all subjects. Note that the difference in the peaks of these curves matches the difference between response amplitudes on correct and incorrect trials in voxels offset 36° from the sample, as shown in Fig. 3B. E: the color of the lines signifies correct (black) and incorrect (blue) trials; solid lines indicate the squared slope divided by within-subject trial-by-trial variance as in B–D, and dashed lines indicate the ±1 SE across subjects. Here the curve peaks at an offset of 11° from the sample, where again the prediction of optimal off-channel gain would be at 0°. F: across-subject mean slope²/variance metric on correct and incorrect trials at the sample orientation. Error bars represent ±1 SE across subjects.