Oxytocin and Interpersonal Motor Resonance

Among different social cues from the environment, the eyes constitute a very salient source for initiating social interaction or communication. Interestingly, previous work from our (Prinsen et al., 2016) and other labs demonstrated that direct eye contact between two individuals can readily evoke an increased propensity to 'mirror' other peoples' actions. Particularly, using transcranial magnetic stimulation (TMS), the investigators showed that mirror-motor mapping at the level of the primary motor cortex (M1), also known as "interpersonal motor resonance" (IMR), is significantly increased upon the observation of actions accompanied by direct eye contact, compared to the observation of actions accompanied by averted eye gaze.

With the present study, the investigators aim to investigate the role of eye contact on IMR further, and in particular, explore whether administration of the 'prosocial' neuropeptide oxytocin (OT) can influence eye-contact induced IMR. In general, OT is known to play an important role in promoting prosocial behavior and the perception of socially-relevant stimuli, such as eye gaze. To date however, the link between OT and IMR is less clear.

In the present study, the investigators want to explore how a single-dose of intranasally administered OT can modulate interpersonal motor resonance (IMR) and/or the enhanced effects of eye contact on IMR. To investigate the effects of exogenous OT administrations, the investigators adopted a double-blind, within-subjects (cross-over), randomized, placebo-controlled trial. The investigators will recruit approximately 30 neurotypical young adults males between 18 - 35 years old. Since a cross-over design is included, subjects will participate in two sessions, separated by one week. Participants will be randomly assigned to receive a single dose of OT (24 international units) or placebo nasal spray at the first and second session.

In each session, the non-invasive brain stimulation technique 'transcranial magnetic stimulation' (TMS) will be used at the level of the primary motor cortex to obtain an end-state measure of unconscious 'mirror-motor mapping' or IMR. During TMS, participants will observe video stimuli of a model performing simple, intransitive hand movements combined with either direct or averted gaze. Additionally, behavioral measures will be included: social attachment and social responsiveness will be assessed via self-report questionnaires and eye tracking technology will be included to monitor participant's spontaneous gaze behavior.

The main statistical analysis of the neurophysiological data will have the within-subjects factor of administered nasal spray (OT or PL), observed gaze direction (direct or averted gaze) and observed movement (opening hand movement or no movement). Furthermore, the link between the neurophysiological (TMS) and behavioral measures (questionnaire data and gaze behavior) will be investigated.

Eligibility Criteria:
Inclusion Criteria:

* Male
* Young adults (between 18 - 35 y/o)
* Right-handed

Exclusion Criteria:

* Left-handed
* Any neuro(psycho)logical / psychiatric illness.
* Motor dysfunctions of the hands / arms.
* Any contradiction to TMS research as assessed with the TMS screening list: no pacemaker, implanted defibrillator, ear implant / a cochlear implant, insulin or implanted pump, a neurostimulator or ventriculoperitoneal shunt, any metallic object in the eyes (metallic fragments)