Multi-input GNL-HybELS: An automated tool for the analysis of oculomotor dynamics during visual-vestibular interactions

The eyes play a major role in our everyday activities. Eye movements are controlled by the oculomotor system, which enables us to stay focused on visual targets, switch visual attention, and compensate for external perturbations. This system´s response to isolated visual or vestibular stimuli has been studied for decades, but what seems to be more critical is to know how it would respond to a combination of these stimuli, because in most natural situations, multiple stimuli are present. It is now believed that sensory fusion does not affect the dynamics of oculomotor modalities, despite studies suggesting otherwise. However, these interactions have not been studied in mathematical detail due to the lack of proper analysis tools and poor stimulus conditions. Here we propose an automated tool to analyze oculomotor responses without a-priori classification of nystagmus segments, where visual and vestibular stimuli are uncorrelated. Our method simultaneously classifies and identifies the responses of a multi-input multi-mode system. We validated our method on simulations, estimating sensory delays, semicircular canal time constant, and dynamics in both slow and fast phases of the response. Using this method, we can now investigate the effect of sensory fusion on the dynamics of oculomotor subsystems. With the analysis power of our new method, clinical protocols can now be improved to test these subsystems more efficiently and objectively.