Fig. 4

Zebrafish larvae display different levels of asymmetric OKN under the symmetric stimulus

(A) A typical eye-position trace of a single larva with an asymmetric optokinetic nystagmus (OKN) under 10/10 symmetric alternating (SA) stimulation and the following negative optokinetic afternystagmus (OKAN). The bottom plots show magnifications to demonstrate the transition phases from OKN to inter- and post-stimulatory periods, respectively.

(B and E) The stimulus image pattern and the stimulus velocity are shown as horizontal bars and lines, respectively.

(C and D) The slow-phase velocity (SPV) of (A, color line) is compared to the median ± median absolute deviation of 29 subjects (black line with gray shadow).

(F and G) The difference in SPVs between the individual larva (color line in C and D) and the population median (black line in C and D). Dashed lines extend from (E) to (F and G) illustrate the time windows for further analyses in (H–K).

(H) The ΔSPV probability distribution of 29 fish during the early and late periods. Two lines demonstrate the fit of distributions with Gaussian function.

(I) The late ΔSPV plotted over the early ΔSPV. The slope of the linear regression line (solid line) is significantly smaller than 1 (p = 1.79e-08; interactive analysis of covariance) and the slope of the dashed line (temporally shuffled data; p = 4.21e-06; interactive analysis of covariance).

(J) The changes in ΔSPV across stimulus phases (late ΔSPV – early ΔSPV, ΔΔSPV) plotted over the early ΔSPV. The slope of linear regression line (solid line) is significantly lower than the slope of the dashed line (temporally shuffled data; p = 4.21e-06; interactive analysis of covariance).

(K) The changes of the eye movements in the dark before and after OKN (post-ΔSPV – pre-ΔSPV, ΔΔSPV) plotted over the early ΔSPV. Filled circles represent the data of the animal shown in (A). Black solid lines demonstrate the linear regression fit of recorded data. Considering the starting direction of alternating stimulation was randomized, we aligned the first stimulus direction as positive instead of left or right. Therefore, the plots show one eye started with a nasalward movement (blue trace) and another eye started with a temporalward movement (red trace). p, p values; Pearson correlation. R, correlation coefficients; Pearson correlation.