Impact of Stimulation Duration in taVNS-Exploring Multiple Physiological and Cognitive Outcomes

Area of Science:

• Neuroscience
• Neuromodulation
• Autonomic Nervous System

Background:

• Transcutaneous auricular vagus nerve stimulation (taVNS) modulates locus coeruleus (LC) noradrenergic activity.
• Optimal taVNS parameters and reliable outcome measures remain unclear.
• Understanding taVNS effects is crucial for its therapeutic application.

Purpose of the Study:

• To compare the effects of short (3.4 s) versus long (30 s) taVNS durations.
• To investigate taVNS effects on physiological and cognitive outcomes.
• To determine reliable parameters for taVNS-induced LC modulation.

Main Methods:

• Double-blind, sham-controlled study with 29 healthy young adults.
• Assessed salivary alpha-amylase, cortisol, pupillary responses, EEG, and cognitive tasks (Go/No-Go, Stop Signal).
• Compared real vs. sham taVNS for two stimulation durations.

Main Results:

• Longer (30 s) taVNS significantly increased salivary alpha-amylase compared to sham.
• Shorter (3.4 s) taVNS led to prolonged reaction times and increased errors in the Go/No-Go task.
• Increased pupillary light reflex acceleration was observed with shorter taVNS; other measures showed no significant differences.

Conclusions:

• Prolonged taVNS (30 s) effectively increases salivary alpha-amylase, consistent with LC modulation.
• Short taVNS (3.4 s) produced unexpected cognitive and pupillary effects, not explained by increased LC activity.
• Further research is needed to clarify taVNS mechanisms and optimize stimulation protocols.