Fig. 6: Control paradigms - Fixation Off, Fixation On and example unit activity.
Trials started with a fixation spot, cueing the animal to bring and maintain gaze within a fixation window (300 ms), following which a drifting stimulus was presented monocularly. a, During Fixation Off, the fixation spot was removed at stimulus onset, thus inducing OKN. b, During Fixation On, the stimulus was presented without removal of the fixation spot, and the animal was required to maintain its gaze within a window (±1 or ±2°) until the trial ended, to receive a juice reward. c, During each trial, a stimulus drifting in one of eight different directions (pseudorandomized across trials) was presented. d, Whisker box plots (for box plot description, see statistical information, methods) displaying the distribution of standard deviations (STD) estimated from the eye movement signal (y-coordinate) elicited on individual trials during stimulus presentation (0–1000 ms). For Fixation On, either all (n = 187) or selected trials (n = 95), which displayed lower variance in the eye movement (E.M.) signal were analyzed (see methods). The STD was significantly reduced (Wilcoxon rank-sum test, two-sided, *** denotes p ≤ 0.001, Fixation Off vs. Fixation On (all trials), p = 7.86*10−69, Fixation On (all trials) vs. Fixation On (low E.M. variance), p = 9.07*10−5, Fixation Off (all trials) vs. Fixation On (low E.M. variance), p = 6.09*10−46) during Fixation On as compared to Fixation Off trials (n = 239). The results presented in this figure were computed with data from two animals pooled together. e and f show spike density functions overlaid on spike raster plots depicting the responses of two units to eight different motion directions during the two paradigms. The middle polar plots display the tuning curves of each unit (average response in Hz to gratings drifting in different directions). Spike rasters are displayed for first ‘n’ trials of every motion direction presentation. Here, n is the minimum number of trials presented to the animal across any motion direction during a given paradigm. PSTHs and tuning curves were computed taking all trials (of a given motion direction) into account. e, Example Unit 1 displays a stronger response to a stimulus drifting downwards during both paradigms. The unit displayed in f responds strongly to two opposite directions of motion, thus displaying orientation preference. Although the firing rate was higher during the Fixation off paradigm, the unit displayed similar preference across both paradigms. Source data are provided as a Source Data file.
