J Neurophysiol. 2020 Jul 29. doi: 10.1152/jn.00697.2019. Online ahead of print.
We stabilize the dynamic visual world on our retina by moving our eyes in response to motion signals. Coordinated movements between the two eyes are characterized by version when both eyes move in the same direction and vergence when the two eyes move differently. Vergence eye movements have been proposed to be important for tracking objects in three dimensions and may be elicited in primates by both differences in the spatial signals, or disparity, or by differences in the motion that the two eyes receive. These vergence eye movements require the integration of left and right eye inputs, but it remains unclear which neural circuits are responsible for the integration that leads to these eye movements. To address this issue, we measured vergence eye movements in mice using a stereoscopic stimulus that is known to elicit vergence eye movements in primates. We found that the primary signal that drives vergence eye movements is the difference in motion presented to each eye, whereas spatial disparity cues had little impact on vergence. We also found that the vergence eye movements we observed in mice were not affected by silencing visual cortex, or by manipulations that disrupt the normal development of binocularity in visual cortex. Instead, we demonstrate that right and left eye motion cues in rodents could be described by a summation of motion signals that occurs outside of the visual cortex.