This study investigates the effects of transcutaneous auricular vagus nerve stimulation (taVNS) on cognitive performance in healthy adults. The study uses a sham-controlled, cross-over design in which each participant receives both active taVNS and sham stimulation in separate sessions. Each participant completes both conditions (active and sham) in a randomized order using a crossover design. Cognitive performance will be assessed before and after each session using standardized tests. The study also explores whether males and females respond differently to taVNS, in order to identify potential sex-related differences in cognitive outcomes.
Healthy young adults aged 18-30 years
Ability to provide informed consent
Right-handed participants (to reduce variability in cognitive performance)
Normal or corrected-to-normal vision and hearing
History of neurological or psychiatric disorders
Cardiovascular disease
Use of psychoactive medications
Substance dependence, including alcohol, illicit drugs, or nicotine
Crossover
Active taVNS
DeviceActive taVNS will be delivered bilaterally to the cymba conchae and tragus regions using the VaguStim device. Stimulation parameters follow cognitive-neuroscience standards to minimize cardiac side effects: biphasic waveform, 25 Hz frequency, 250 μs pulse width, and intensity individually adjusted below the sensory threshold (0.5-4 mA). Each stimulation session lasts 20 minutes. This intervention corresponds to the Active taVNS Stimulation arm.
Sham Stimulation
DeviceSham stimulation will be delivered using the same VaguStim device, but electrodes will be placed bilaterally on the earlobe, an area not innervated by the vagus nerve. Device parameters will be set to match the active condition, but no true vagus nerve stimulation is delivered. This procedure controls for placebo and participant expectancy effects. This intervention corresponds to the Sham Stimulation arm.
CogniFit Digital Battery
Cognitive performance will be evaluated using the CogniFit digital cognitive battery, which assesses multiple cognitive domains including attention, working memory, executive functions, and processing speed. The battery will be administered once at baseline (Visit 1). It will be administered again immediately after Active stimulation in Visit 2 and immediately after Sham stimulation in Visit 3. Changes in cognitive scores between baseline and post-stimulation sessions will be compared to determine the acute cognitive effects of active vs. sham taVNS.
Heart Rate Variability (HRV)
Heart rate variability will be assessed using the Polar H10 chest strap or another validated portable HRV device widely used in research. Five-minute recordings will be obtained during resting state and during stimulation. Time-domain parameters (RMSSD, SDNN) and frequency-domain parameters (LF/HF ratio) will be analyzed.
Perceived Stress Levels (PSS)
The Perceived Stress Scale (PSS) will assess participants' perceived stress levels over the past month. Higher scores indicate higher perceived stress.
State and Trait Anxiety (STAI)
The State-Trait Anxiety Inventory (STAI) will measure acute state anxiety (STAI-S) and general trait anxiety (STAI-T).
Self-Reported Side Effects
A researcher-developed side-effects questionnaire will be used to record any discomfort, tingling, dizziness, or other adverse effects following stimulation.
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