Transcutaneous Auricular Vagal Nerve Stimulation Impact on Auditory Processing in Healthy Subjects

This clinical study investigates the effects of transcutaneous auricular vagal nerve stimulation (taVNS) on auditory processing abilities in healthy individuals. The research aims to determine whether non-invasive vagus nerve stimulation can enhance central auditory processing (CAP) functions, specifically temporal sequencing skills measured through Frequency Patterns Test (FPT) and Duration Patterns Test (DPT).

Methodology: The randomized, crossover study involved 70 healthy participants aged 18-40 years, divided into active taVNS (n=40) and sham control (n=30) groups. All subjects underwent comprehensive screening including MoCA cognitive testing (score ≥21), pure tone audiometry (thresholds ≤25 dB from 250-8000 Hz), and established CAP assessments. The experimental group received 15 minutes of left ear taVNS using biphasic square wave stimulation (20Hz, 250µs pulse width) at sensory threshold level, while controls received sham stimulation with inactive electrodes.

Key Findings: The study measured immediate pre- and post-stimulation changes in auditory pattern recognition through standardized FPT and DPT protocols. FPT assessed frequency pattern identification (1122Hz vs 880Hz tones) while DPT evaluated duration discrimination (500ms vs 250ms tones at 1000Hz). Both tests involved 50 stimulus sets (25 per ear) with scoring accounting for both correct and reversed pattern responses (Rev Plus and Rev Minus scoring systems).

Significance: This research provides novel insights into neuromodulation approaches for auditory processing, with potential implications for both healthy populations (e.g., musicians, language learners) and clinical applications for central auditory processing disorders. The study design carefully controlled for confounding factors by excluding professional musicians, left-handed individuals, and those with hearing/cognitive impairments, while maintaining gender balance.

Technical Specifications: All testing occurred in IAC-standard soundproof booths using Interacoustic AC40 audiometry equipment with TDH39 headphones. taVNS was administered via VAGUSTIM TENS device with ultrasound gel-enhanced electrodes placed on the left auricular concha. Safety protocols limited stimulation duration to 15 minutes to prevent potential side effects.