Identifying Neurosensory Solutions to the Binding Problem in Animal Behavior

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Human and animal behavior is guided by continuous and often complex sensory input. Nervous systems must parse this input stream and bind together those pieces corresponding to actual objects in the environment. As an illustration, consider the command to STOP. The human visual system effortlessly binds an octagonal shape with red coloration into a unified visual percept that elicits stopping behavior. Likewise, different sounds in the spoken word "stop" become bound into an auditory percept that also elicits stopping behavior. Efforts to understand how nervous systems solve these so-called "binding problems" have advanced the fields of cognitive and computational neuroscience. By comparison, much less is known about how nonhuman animals create bound percepts that correspond to the variety of things of interest to animals (e.g. prey, predators, mates, communication signals). Hence, important knowledge gaps remain concerning the brain mechanisms that allow animals to solve binding problems. This project integrates behavioral and electrophysiological experiments to uncover general mechanisms of auditory perceptual binding in an animal model for which vocal communication in noisy social environments is key to successful reproduction. This research is important because basic knowledge of neurosensory mechanisms that enable animals to solve auditory binding problems could benefit society by helping to improve hearing prosthetics and speech recognition systems, which perform poorly in noisy acoustic scenes. This research will also lead to answering new questions about how neural systems shape the evolution of communication behaviors. In addition, the project will create research experiences for a minimum of 15 undergraduates, advance the training of a postdoctoral scholar, and integrate research and teaching with public outreach aimed at elementary school kids in a large metropolitan area. The project investigates auditory binding in green treefrogs (Hyla cinerea), a well-known animal model in studies of hearing and sound communication. Aim 1 uses behavioral experiments to identify cues that promote auditory binding. Two experiments will test the hypothesis that synchronous onsets/offsets, common spatial origin, and harmonic relatedness function to bind together separate parts of the frequency spectrum of vocalizations analogous to formants in human vowel sounds. Aim 2 involves electrophysiological recordings from single neurons in the auditory midbrain to identify neural correlates of auditory binding. Three experiments will test the hypothesis that changes in the responses of neurons sensitive to spectral combinations correlate with changes in the behavioral decisions made in response to manipulations of the auditory binding cues from Aim 1.