Cortical circuits for dynamic auditory perception and learning
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 two of our recent studies that elucidate the function of specific inhibitory neuronal populations in sound encoding and perception. First, we found that the most common class of interneurons, parvalbumin-positive (PVs), 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 interneurons, somatostatin- positive interneurons (SOMs), 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. We found that SOMs selectively reduced excitatory responses to frequent tones, whereas PVs amplify adaptation by providing non-specific inhibition. More recent experiments demonstrate that the role of SOMs extends to other forms of adaptation to temporal regularities. These results expand our understanding of how specific cortical circuits contribute to auditory perception in everyday acoustic environments.
Dr. Maria Geffen is an Assistant Professor of Otorhinolaryngology at the University of Pennsylvania.
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