Fig. 2: Lamprey optokinetic responses.

a Graphical illustration of the normalized EMG amplitudes (left) and number of spikes (right) of the evoked EMG activity in the dorsal rectus of one animal during optokinetic stimulations in the roll plane across a range of velocities. b Representative traces at three different velocities during roll stimulations. The dotted rectangle indicates the duration of the optokinetic stimulation. c Graphs showing the EMG activity in the dorsal rectus of one animal during optokinetic stimulations in the pitch plane across a range of velocities. d Representative traces at three different velocities during pitch stimulations. e, f Mean EMG amplitudes and spikes reflecting the EMG activity in the dorsal rectus in response to optokinetic stimulation in the roll (e) and pitch (f) planes combining the data from six animals for roll, and five for pitch. A repeated measures ANOVA revealed significant effects of stimulation velocity on EMG amplitudes (F[3, 51] = 7.858, p < 0.001) and spikes (F[3, 51] = 3.366, p = 0.026) in the roll plane, as well as EMG amplitudes (F[4, 56] = 5.057, p = 0.001) in the pitch plane. g Graph showing that EMG activity does not increase in parallel to the speed of optokinetic stimulation in the yaw plane. Representative traces are shown in h. i Reliable optokinetic responses in the roll plane were however observed in animals lacking a yaw plane response. Holm corrections were carried out for all analyses. The shaded areas in the graphs denote error bands. Source data are provided as a Source Data file. Roll plane analysis was carried out on n = 52 independent samples from three animals, while pitch plane analysis was carried out on n = 57 independent samples from three animals.