Parvalbumin and somatostatin interneurons support distinct computations during auditory scene analysis

Abstract

Auditory scene analysis requires cortical circuits to preserve target-sound representations while suppressing interference from competing sound sources. Although spatial separation between tar{-}get and masker sounds can substantially improve perception, the inhibitory circuit mechanisms that transform spatial separation into improved target sound representations remain poorly un{-}derstood. Here, we used a multi-speaker auditory environment to present target sounds alone (clean) or together with spatially distributed competing white noise (masked) trials while record{-}ing auditory cortical activity in awake mice. By combining electrophysiology, cell-type-specific optogenetic suppression, and spike-distance-based neural classifiers, we examined how parval{-}bumin (PV) and somatostatin (SST) interneurons contribute to spatial processing in complex auditory scenes. PV and SST interneurons made dissociable, context-dependent contributions. PV suppression broadly altered spatial tuning properties, including tuning width, modulation depth, centroid, and sparseness, and reduced target-sound discriminability under clean condi{-}tions. In contrast, SST suppression produced comparatively modest effects on spatial tuning but selectively impaired neural discrimination only during masked trials thereby weakening the im{-}provement in target discrimination normally associated with spatial release from masking. Thus, the interneuron population that most strongly altered spatial tuning was not the population that most strongly disrupted masked discrimination. This reveals a dissociation between cortical in{-}hibitory mechanisms supporting spatial receptive-field structure and those supporting target-masker segregation. Together, these findings suggest that PV-mediated inhibition refines the fi{-}delity of auditory cortical representations, whereas SST-mediated inhibition enhances separation of simultaneously spatially competing sound sources, providing complementary inhibitory mecha{-}nisms for auditory scene analysis.