Fig. 9: Locomotion evoked eye movements.

a Schematic showing the semi-intact lamprey preparation used to monitor body and eye movements. The rostral segment up to the spinal cord is dissected according to the same principles as the ex vivo preparation, exposing the brain and the eyes. The remainder of the body and tail were kept intact in order to allow locomotion. A video camera was placed coupled to a microscope to film the preparation from above. b Either spontaneous or tactilely induced locomotion (by gently pinching the tail) was recorded, and eye and body movements were analyzed over time. Eye movements synchronized with swimming activity were observed. Images show two different positions of the eyes and the tail during a swimming episode. c Trajectories of the tail (black) and eyes (green, right eye; purple, left eye) showing that coordinated movements of both eyes occur together with tail movements. d Although these movements were less consistent, they were preserved after visual and vestibular inactivation. e Graph showing the positive correlation (Pearson’s correlation analysis, r (1166) = 0.707, p < 0.001) between the right and left eyes, indicating their synchronization. f, g Graphs showing that tail and eye movements are correlated both before (f; Pearson’s correlation analysis, r (1160) = −0.553, p < 0.001), and after (g) visuovestibular inactivation (r (1582) = −0.450, p < 0.001), indicating that the observed coupled eye movements are generated by locomotion corollary discharges. Source data are provided as a Source Data file.