The Effect and Mechanism of taVNS in Modulating Human Social Attention

Condition(s) studied

Investigational drug(s) / intervention(s)

taVNS: bilateral Transcutaneous Auricular Vagus Nerve Stimulation on earlobe

taVNS: Transcutaneous Auricular Vagus Nerve Stimulation on left tragus

taVNS: taVNS only on the right tragus

taVNS: taVNS on the bilateral tragus

Study summary

The objectives of this study are to investigate:

1. whether non-invasive transcutaneous auricular vagus nerve stimulation (taVNS) can enhance human interest in social stimuli in free-viewing and stressful tasks;
2. whether its effect on brain function occurs via modulating endogenous oxytocin release;
3. how the stimulation site and various parameters of taVNS should be set to effectively promote the above-mentioned changes in brain function.

The main questions it aims to answer are:

1. Does taVNS facilitate a preference for social relative to non-social stimuli in both free-viewing and stressful tasks?
2. Does taVNS increase peripheral concentrations of the neuropeptide oxytocin, and whether these changes are associated with enhanced social attention?
3. Does taVNS stimulation of the right tragus, left tragus, or bilateral tragus sites produce the strongest effects on oxytocin release and social attention?

Investigators will compare the effects of taVNS targeting the left tragus, right tragus, or bilateral tragus with ear-lobe sham stimulation (no vagal activation). Eye-tracking will be used across multiple experimental paradigns. For measurements of oxytocin (OT) and arginine vasopressin (AVP), saliva samples will be collected at baseline, immediately after taVNS, 20 min post-stimulation, and 30 min post-stimulation. Investigators will test whether (a) taVNS facilitates social attention, and (b) its effects are associated with elevated OT and AVP release.

Investigators hypothesize that taVNS will enhance social attention and oxytocin release, that changes in social attention will be associated with the magnitude of oxytocin release, and that bilateral tragus stimulation will produce the strongest effects on both social attention and oxytocin release.

Eligibility

Primary outcome measure(s)

• Fixation time on different areas of interest (AOIs) in free viewing tasks — baseline: one week before the stimulation; post: immediately after the 30 min sham (earlobe) or taVNS (transaural vagal stimulation) stimulation.
  The total time spent viewing specific AOIs in free viewing tasks will be recorded
• Fixation counts on different AOIs in free viewing tasks — baseline: one week before the stimulation; post: immediately after the 30 min of sham or taVNS stimulation
  The number of fixations on specific AOIs during presentation of visual stimuli will be recorded
• Errors made in the stressful antisaccade task — baseline: one week before the stimulation; post: immediately after the 30 min of sham or taVNS stimulation
  The number of errors in the direction opposite to the required direction
• Response time in the stressful antisaccade task — baseline: one week before the stimulation; post: immediately after the 30 min sham or taVNS stimulation
  Time taken to make the first saccade towards the required direction

Trial sites (1)

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