The Role of Cortical Inhibitory Interneurons in Auditory Signal Detection

62 pagesFor years, researchers have been trying to uncover how different auditory areas in the brain allow us to segregate signals from noise. The goal of this study was to use a mouse model to understand how two types of cortical inhibitory interneurons found in the auditory cortex, known as somatostatin-expressing (SOM) and parvalbumin-expressing (PV) interneurons, contribute to our perception of sound masked by noise. We hypothesized that inactivating auditory cortical SOM interneurons would decrease mice’s ability to detect a tone masked by noise when the bandwidth of the background noise was broadband. We expected a similar decrease when PV interneurons were inactivated regardless of the bandwidth of the background noise. To test these hypotheses, we taught transgenic SOM-ArchT and PV-ArchT mice how to perform a behavioral task where they had to determine if a pure tone was present in background noise. We then implanted optical fibers over each mouse’s auditory cortex and they performed the same task while having their respective interneurons inactivated, which was achieved through an interaction between the light-sensitive ArchT protein found in the interneurons and green light delivered by a laser output box. We found that inactivating SOM interneurons decreased the percentage of trials in which the mice were able to detect a tone masked by noise in all bandwidths of background noise, while inactivating PV interneurons did not affect the mice’s ability to do so, showing that signals from PV interneurons might not be needed for mice to perform this task. These findings allow us to better understand the roles that different sources of inhibition play when it comes to our ability to detect a sound masked by noise