Excitatory-inhibitory circuits in auditory processing

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 specific inhibitory neuronal populations in sound encoding and perception. First, our results demonstrate that cortical inhibition can improve or impair acuity of innate and learned auditory behaviors. Second, we found that a specific type of cortical inhibitory neurons regulates adaptation in the auditory cortex to frequent sounds, in a stimulus-specific fashion. More recent experiments found that the role of these interneurons extends to other forms of adaptation to acoustic temporal regularities. Third, we identified that a center for emotional learning, the basolateral amygdala, gates cortical auditory responses by engaging thalamic inhibition. These results expand our understanding of how inhibitory-excitatory neuronal circuits contribute to auditory perception in everyday acoustic environments.