Vagus nerve stimulation strengthens beta- and gamma-rate auditory steady-state responses in rat cortex

Background: Gamma entrainment using sensory stimulation (GENUS) is under study as a treatment for neurological disease, but cortical engagement is variable. Vagus nerve stimulation (VNS) modulates cortical state and sound-evoked beta-gamma activity, suggesting that it may strengthen responses to rhythmic sensory input. Objective: To determine whether VNS strengthens auditory steady-state responses across beta and gamma rates and whether the effect depends on cortical region and sensory drive. Methods: Electrocorticography (ECoG) was recorded from core and belt auditory cortex, insular auditory field (IAF), and anterior insular cortex (AIC) in seven isoflurane-anesthetized rats before and 90 min after initiation of 30-Hz cervical VNS. Responses to 500-ms click trains at 20 and 40 Hz were quantified using inter-trial phase clustering (ITPC), event-related spectral perturbation (ERSP), and debiased weighted phase-lag index (WPLI). Results: VNS increased click-evoked P1-N1 amplitude. During 40-Hz trains, 40-Hz ITPC and ERSP increased only in auditory core. During 20-Hz trains, 20-Hz ITPC increased in core, belt, and IAF, whereas ERSP increased only in core; 40-Hz harmonic responses increased only in core. AIC showed no change. Within auditory cortex, WPLI increased selectively at frequencies present in each click train and not in the alpha band. Conclusions: VNS strengthened beta- and gamma-rate stimulus-locked responses in auditory-driven cortex without globally increasing synchrony. VNS may therefore enhance auditory cortical target engagement during GENUS, although effects on disease pathology or clinical outcomes remain untested.

Source: arXiv:2610.29042v1 - http://arxiv.org/abs/2610.29042v1 PDF: https://arxiv.org/pdf/2610.29042v1 Original Link: http://arxiv.org/abs/2610.29042v1