The Effect of Visual Stimuli on Sound Representation in the Macaque Inferior Colliculus

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PROJECT SUMMARY/ABSTRACT: Visual cues can help the brain localize sounds. At the neural level, the brain might accomplish this by altering its response to sounds in the presence of visual signals. This could occur for single sounds, allowing the brain to use visual information to guide sound localization. This could also occur for multiple sounds, allowing the brain to connect visual information to the appropriate sound in a noisy environment. To test these possibilities, two rhesus macaques will perform a task in which they will localize one or two sounds in the presence or absence of accompanying lights. While the monkeys perform this task, we will record from single and multiple neurons in the inferior colliculus (IC), a critical auditory region that receives visual input and has visual and eye movement-related responses. To test whether visual cues alter the representation of single sounds, monkeys will localize a sound, light, or sound-light pair at a shared location. We expect that IC neurons will have a different response to sounds than to sound-light pairs. To test whether visual cues alter the time-varying response to multiple sounds, monkeys will detect two simultaneous sounds, each of which dominates the response of the neuron during distinct periods of time. We will compare IC neurons’ responses to two sounds, two sounds with one paired to a light, and two sounds with both paired to a light. When one sound is paired to a light, we predict that IC activity will skew toward the visually-paired sound. These experiments will help clarify the influence of visual cues on auditory responses and will provide insight into how the brain combines visual and auditory information into a single perceptual object. In addition to the proposed research, a training plan will also be carried out at Duke University, an environment offering many resources for both academic and professional development. The fellowship training plan takes advantage of opportunities both at Duke and in the community to support preparation for a research career with an emphasis on science communication. The proposed research will also facilitate professional development through the advancement of technical, analytical, and communication skills.