Vision helps us hear. For example, lip reading aids speech comprehension, and visual cues are thought to be critical for learning how to localize sounds. Visual-auditory interactions are usually considered to be a cortical phenomenon, but mounting evidence suggests that cross-talk between sensory systems begins well before the cortical stage. In this project, we investigate visual influences over the auditory processing at the earliest point that they occur: in the ear. The auditory pathway has a robust system for modulating the processing of incoming auditory signals via the motoric actions of outer hair cells and middle ear musculature. These structures are under descending control from the brain, providing potential routes for visual-related signals to influence auditory processing. This system is affected by movements of the eyes: we have recently reported a previously unknown oscillation of the eardrum that is time locked to the occurrence of saccades and occurs in the absence of a delivered sound. We hypothesize that the processes that underlie this eye movement-related effect on peripheral auditory processing play a role in reconciling the disparities in visual and auditory spatial signals that accompany eye movements. We will test this hypothesis by determining what eye movement properties determine the properties of the eardrum oscillation, where in the oculomotor system commands that contribute to this effect originate; and how eye-movement related peripheral processing changes in conjunction with changes in the mapping between visual and auditory space. Together, these experiments will shed light on how the brain tunes its auditory input to coordinate with the visual system. The discovery of multisensory signals at the very gateway of the auditory pathway represents a fundamental shift in our understanding of the scope and mechanisms employed not only in service of multisensory integration, but also on what was previously supposed to be unimodal processing. The findings will be relevant to disorders involving hearing as well as other conditions that involve visual and auditory deficits, such as dyslexia, auditory processing disorder, Meniere's disease, autism, schizophrenia, and age-related cognitive impairments.
HEALTH RELEVANCE STATEMENT How the visual and auditory systems interact at the earliest stages of auditory processing is relevant to both hearing disorders and a variety of conditions involving visual and auditory deficits, such as dyslexia, auditory processing disorder, Meniere's disease, tinnitus, autism, schizophrenia, and age-related cognitive impairments.
