Visual Cues Modulate Auditory Responses in the Macaque Inferior Colliculus

Abstract

How the brain uses multisensory cues to process complex sensory environments remains a key question in neuroscience. Of particular interest is whether relatively early sensory areas, which are commonly considered to be unisensory in function, might take in information from other sensory modalities to inform the representation of the primary modality of interest. We explored how visual cues might inform the representation of sounds in the macaque inferior colliculus, a subcortical auditory region that receives visual input and has visual and eye movement-related responses. Using in vivo single-unit extracellular recordings, we observed neuronal responses in the inferior colliculus while two monkeys performed a localization task involving both auditory and visual stimuli. We found that pairing a visual cue with a sound can change a neuron’s response to that sound, even if the neuron is unresponsive to visual input alone. Visual cues also enhance localization behavior in both spatial precision and temporal latency. Finally, when two simultaneous sounds are present and one sound is accompanied by a visual cue, neurons’ responses to the two stimuli on individual trials may correlate with each monkey’s behavior during the task. Together, these results suggest that the inferior colliculus uses visual cues to alter its sound responsiveness and inform perceptual behavior, providing insight into how the brain combines multisensory information into a single perceptual object at a relatively early stage of the auditory pathway.