Brown University School of Engineering

Engineering Seminar: Biomedical Engineering

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Wednesday, March 22, 2017 4:00pm - 5:00pm

"Top-Down Control of Representations in the Auditory System" will be presented by Stephen David, Ph.D., Assistant Professor at Oregon Health and Science University. Abstract: Studies of attention and other behavioral manipulations have revealed diverse task-related changes in neural activity in auditory cortex, which have yet to be integrated into a coherent theory of how internal state influences sensory processing. To better understand the diversity of variables that reflect behavioral state, we developed a paradigm to isolate the effects of task engagement, selective attention and behavioral effort in tasks requiring the same auditory discrimination. Ferrets were trained to respond to a target tone masked by one of two simultaneous narrowband noise streams and to ignore catch tones in the other. Selective attention was controlled by adjusting the probability of the target occurring in one or the other stream, and relative effort was controlled by adjusting the expected signal-to- noise level of the target tone. We recorded single-unit activity in primary auditory cortex (A1) during behavior and during passive presentation of task stimuli. When animals directed attention to a target sound that fell in the receptive field of a neuron, responses to the distractor noise were suppressed. Decreasing target SNR decreased spontaneous firing rate in A1 but did not a have systematic effect on sound-evoked activity. Our data demonstrate a dissociation between two state variables—selective attention and listening effort—on activity in A1. Ongoing studies are exploring the relationship between pupil-index state, a hypothesized measure of arousal, and changes in attention and effort, as well as their combined influence on populations of simultaneously recorded cortical neurons. Biography: Stephen V. David is Assistant Professor in the Oregon Hearing Research Center at Oregon Health and Science University. Before coming to OHSU, Dr. David completed a postdoctoral fellowship with Shihab Shamma in the Institute for Systems Research at the University of Maryland, College Park. In May 2004, he completed a Ph.D. in Bioengineering at the University of California, Berkeley, studying vision and attention with Jack Gallant. Dr. David’s research interests are in the neural basis of sensory perception, particularly in the auditory system. Current projects use computational approaches to characterize auditory neural representations while manipulating context through associative learning, environmental noise, hearing loss, attention and arousal. Website: http://hearingbrain.org/