Fig. 5: Optic flow calibrates integration of change in HD.

a, Experimental protocol (top). Middle, example offset (blue dots) during fast cue rotation (3° per s) showing persistent drift bias after cue removal. The solid red lines show low-pass filtered offset. Bottom, cue location (dashed yellow) and measured HD (solid black) relative to baseline cue location. Darkness periods are shown in grey. b, Example fast-cue-rotation session showing stabilization of the internal representation with an overshoot past the baseline orientation (top). Bottom, the same as in a. c, Mean drift speed during cue rotation (rot.) for fast (light blue) and slow (dark blue) sessions. Data are across-session mean ± s.d. Top left inset: subtraction of the cue-rotation speed from the average drift speed for individual sessions shows the average deviation of drift-speed with reference to the cue-rotation speed per session. Bottom right inset: comparison of drift-speed s.d. values between fast and slow sessions (two-sided Wilcoxon rank-sum test, P = 0.5262, Z = 0.63). d, The mean offset for fast (light blue; n = 19 events) and slow (dark blue; n = 25 events) sessions (left). The dotted lines correspond to the natural progression of offset if drift speed matched the speed of cue rotation. Data are mean (solid line) ± s.e.m. (shaded area). Right, drift-speed comparison between fast and slow sessions in the first minute after cue removal (Wilcoxon rank-sum test, P = 0.0393, Z = 2.06). All clockwise sessions were reflected across the x axis and transformed into counter-clockwise ones. e, Drift vector field (left). The arrows indicate the direction of mean drift speed and mean drift acceleration (n = 60 sessions). Arrow length was scaled down for illustration purposes. Right, simulated streamlines. The stable regime is highlighted in red. In a–d, fast sessions in which the offset angle at the beginning of the second darkness was within [−180:−145]U[145:180]° were considered, whereas slow sessions in which the offset’s initial position in the second darkness was within [−125:−55]° were included. In e, all sessions were considered regardless of the offset angle at the start of the second darkness. For c and d, data are mean ± s.e.m. with individual datapoints.