Parvalbumin interneurons are essential for tonotopy strength in the auditory cortex

Tonotopy, the spatial organization of neurons based on their sound frequency responses, is a fundamental feature of the auditory pathway, extending from the cochlea to the auditory cortex. While excitatory neurons have been considered necessary for tonotopy in the cortex, the role of inhibitory interneurons remains unclear. Using a novel two-channel widefield Ca2+ imaging system, the 2-Channel Alternating exposure wide-Field Explorer (2-CAFE), we simultaneously measured the sound responsiveness of distinct neuron types in awake mice. Combined with two-photon imaging, we observed that GABAergic interneurons followed a similar tonotopic organization to the conventional auditory maps at both mesoscale and single-cell resolutions. Among the major interneuron subtypes-parvalbumin (PV), somatostatin (SST), and vasoactive intestinal peptide (VIP)-PV interneurons demonstrated a critical role in maintaining tonotopy. Inactivation of PV neurons, but not VIP or SST neurons, significantly weakened the tonotopic strength in the auditory cortex. These findings establish PV interneurons as essential components of auditory cortical tonotopy.