Animals that use acoustic signals to perceive their environment depend on their ability to detect relevant sound signals among an abundance of irrelevant sounds. An early step in this analysis of the auditory scene is the perceptual grouping of the acoustic mixture reaching the ear into coherent representations of sound sources (= Auditory Stream Segregation). This process has been described in a variety of vertebrates. Although auditory scene analysis has been intensively studied in a variety of systems, the understanding of the neuronal processes underlying auditory scene analysis remains limited, and testable neuronal models of auditory stream segregation are currently not available. Recently, auditory stream segregation has been described in one invertebrate system: a katydid auditory interneuron (TN-1) segregates information about bat echolocation cries from a background of male communication calls. This project investigates the neuronal mechanisms underlying auditory stream segregation by TN-1 in katydids (Insecta, Tettigoniidae). Ultimately, the goal is to establish a neuron model to study auditory stream segregation at the levels of ion-channels, cells and networks.
The first part of the project determines the importance of the behavioral context for auditory stream segregation in this system. The segregation performance is compared behaviorally between females that are either receptive or non-receptive to male calls. The second part of the study identifies the mechanisms underlying the suppression of TN-1 responses to male calls, using intracellular recordings from TN-1 dendrites. Changes in membrane conductance are measured in response to adapting stimuli under various experimental situations. The third part of the study tests whether the processes leading to the suppression of responses to male calls occur only in restricted areas of the dendrite, using measurements of membrane conductance and calcium or sodium imaging. This project establishes a new model system and a novel hypothesis to the study of auditory scene analysis and sensory processing in general. It is therefore likely to be an important contribution to neurobiology.
This project includes a direct transfer from research to education: the experimental setup for behavioral tests and extracellular recordings is modified to be suitable for classroom teaching at undergraduate or high school level. This project includes training of several undergraduate and graduate students as well as a postdoctoral associate. This project is part of a larger effort at the University of Missouri to establish graduate and undergraduate training in computational neuroscience.
