Role of neural activity during inter-token intervals in sound sequence discrimination-II, non-primary auditory cortex

Silent gaps between sound tokens are a prominent feature of natural acoustic sequences, yet their role in shaping cortical selectivity for temporal structure remains unclear. Here we tested how varying inter-token interval silence influence neural discrimination of periodic vs aperiodic sound sequences across primary auditory cortex (A1) and non-primary auditory cortices (AuV and AuD) with single unit electrophysiology in anesthetized mice. Non primary cortices spiking activity can discriminate periodic from aperiodic sequences via their selective subpopulations, but including silence does not systematically enhance selectivity, however ITI-dependent selectivity gain is unique to A1 spikes. Pre-subsequent period activity builds up across the sequence, is stronger for periodic than aperiodic sequences, and this buildup is specific to A1 prominently expressed in A1 spikes and in the gamma-band component of A1 LFP while being absent in non-primary auditory cortices.