Hearing perception relies on our ability to tell apart the spectral content of different sounds, and to learn to use this difference to distinguish behaviorally relevant (such as dangerous and safe) sounds. However, the neuronal circuits that underlie this modulation remain unknown. In the auditory cortex, the excitatory neurons serve the dominant function in transmitting information about the sensory world within and across brain areas, whereas inhibitory interneurons carry a range of modulatory functions, shaping the way information is represented and processed. I will discuss the results of our recent studies that elucidate the function of neuronal populations in sound encoding and perception. First, we found that the most common class of inhibitory neurons modulate frequency selectivity of excitatory neurons in the auditory cortex and regulate frequency discrimination acuity and specificity of discriminative auditory associative learning. Our results demonstrate that cortical inhibition can improve or impair acuity of innate and learned auditory behaviors. Second, we found that another class of inhibitory neurons regulate adaptation in the auditory cortex to frequent sounds, in a stimulus-specific fashion. By selectively reducing responses to frequently, but not rarely, occurring sounds, auditory cortical neurons enhance the brain’s ability to detect unexpected events through stimulus-specific adaptation. The role of these inhibitory neurons extends to other forms of adaptation to temporal regularities. Third, I will discuss a study that integrates results from our and other laboratories into a unifying model of the auditory cortex. These results expand our understanding of how specific cortical circuits contribute to auditory perception in everyday acoustic environments.
Dr. Geffen is a leader in the field of auditory neuroscience. She is interested in the way the brain encodes information about the world and how our perception is shaped by our emotional state and experience. She combines computational and biological approaches to study the mechanisms behind dynamic auditory perception, memory and learning.
Dr. Geffen first became interested in systems neuroscience through her undergraduate thesis under mentorship of John Hopfield at Princeton University, in which she explored the mechanics of whisking in rats. She studied texture encoding in the somatosensory system with Christopher Moore at MIT during her first two years of graduate school at Harvard. She completed her Ph.D. in the laboratory of Markus Meister at Harvard University, where she discovered a novel retinal circuit for processing moving images. After her Ph.D., she was a fellow at the Center for Physics and Biology at Rockefeller University, where she worked under mentorship of Dr. Marcelo Magnasco, exploring the dynamics of natural sounds.
Dr. Geffen’s recent discoveries include: identifying a novel cell type that supports hearing of unexpected sounds; establishing the connection between emotional learning and sound perceptual acuity; and elucidating the neuronal code for representation of communication signals in the brain. Her scientific results are regularly published in well-recognized journals, including Nature Neuroscience, eLife and PLoS Biology. Her research accomplishments have been recognized with prestigious awards, including the Burroughs Wellcome Career Award at the Scientific Interface, the Klingenstein Foundation Award in Neurosciences, the Human Frontiers in Science Foundation Young Investigator Award and the Auditory Neurophysiology Young Investigator Spotlight Award. Her research is supported by multiple grants from the NIH as well as from private and international foundations. She serves as a permanent member on an NIH review panel, and has served as the general chair and workshop director for multiple national and international meetings. Dr. Geffen’s trainees have won the Brain Research Foundation Young Investigator Award, Ruth L. Kirschstein National Research Service Award from NIH and the Saul Winegrad Award for Outstanding Dissertation.