Staff who where to run the study left.

This project will apply non-invasive, trans-cutaneous vagal nerve stimulation using various stimulation parameters to young, healthy adults to find the optimal set of parameters to elicit pupil response.

Inclusion Criteria:

• Fluent English speaker with reading and writing proficiency.

Exclusion Criteria:

• Participants with significant visual impairment or ocular illness may be excluded at the discretion of the principal investigator.
• Major medical illnesses including severe neurological illness (e.g. stroke, seizure history), autoimmune disorders, and severe psychiatric diseases (e.g., schizophrenia)
• Any history of brain surgery, tumor, intracranial metal implantation, pacemakers, or other implanted devices.
• Current (i.e. within 48 hours of the session) prescription medication or over-the-counter medication use.
• Illicit alcohol or drug use. Caffeine (e.g, coffee, energy drinks) consumption prior to the visit.