Nonlinear dynamics of a corticothalamic coupled neural mass model reproduce the mechanism of 40 Hz ASSR generation.

Auditory steady-state responses (ASSR) provide a powerful tool for investigating oscillatory dynamics and network synchronization along the auditory pathway. However, existing neural mass models of 40 Hz ASSR have largely focused on cortical microcircuits or macroscopic phenomenology, while neglecting the closed-loop regulation formed by thalamocortical feedforward transmission and thalamic reticular nucleus (TRN)-mediated feedback inhibition. To address this, we constructed an Auditory Corticothalamic Neural Mass Model (ACT-NMM) that investigates cortical pyramidal neurons (Pyr), parvalbumin-positive interneurons (PV), somatostatin-positive interneurons (SST), thalamocortical relay neurons (TCR), and TRN neurons within a delay-coupled corticothalamic loop. By reproducing the steady-state oscillatory patterns observed in the auditory cortex and analyzing parameter-dependent synchronization, phase locking, and frequency locking, the ACT-NMM quantitatively characterizes how thalamocortical interactions shape ASSR dynamics. The results suggest that the auditory cortex acts as the primary generator of the 40 Hz ASSR, whereas the thalamus mainly contributes phase alignment and relay modulation, rather than generating a strong ASSR response independently. These findings demonstrate that ACT-NMM captures the key dynamic features of ASSR generation, providing a physiologically interpretable framework for linking corticothalamic parameters to observed auditory oscillations.