Visual modulation of vestibularly-triggered air-righting in rats involves the superior colliculus

Vision plays two roles in air-righting, it can trigger air-righting in the absence of the labyrinths, and it can modulate the onset and speed of air-righting depending upon the height of the fall. While the visual cortex is known to be necessary for visual triggering, the neural systems necessary for visual modulation are unclear. In this study, the role of the visual cortex and the superior colliculus in visual modulation by rats was analysed. Rats can visually modulate vestibularly-triggered righting, but not trigger righting visually in the absence of the labyrinths. Adult rats with complete neonatal decortication, and adult rats with more specific ablation of the visual cortex were able to visually modulate air-righting. Ablation of the superior colliculi as well as the visual cortex, or ablation of the superior colliculi alone, resulted in loss of the ability to visually modulate air-righting. It is concluded that the superior colliculus is necessary for visual modulation in rats. It is hypothesized that in cats also, the superior colliculus, not the visual cortex, is necessary for visual modulation.