Influence of Oxytocin on Approach-avoidance Tendencies to Social and Non-social Stimuli

The neuropeptide oxytocin (OT) plays an important role in a wide-range of complex social behaviors. Recently however, the 'social' specificity of OT's action has been challenged, considering several observations of non-social effects of OT showing for example that OT reliably reduces stress also in non-social tasks.

To account for these non-social effects of OT, the General Approach-Avoidance Hypothesis of OT (GAAO) has been put forward, positing that OT primarily modulates approach/ avoidance motivational tendencies and behaviors by impacting on the mesocorticolimbic circuitry linked to reward (approach) as well as cortico-amygdala circuits linked to threat (avoidance) (Harari-Dahan and Bernstein, 2014). Since the neural substrates underlying 'social' approach and avoidance are not distinct from those underlying 'non-social' approach and avoidance, the GAAO posits that the modulatory effects of OT should not be limited to social behaviors. In this view, the GAAO puts forward that OT may indeed enhance the attentional salience of many social cues, but not because they are social per se; but because many social stimuli are emotionally-evocative and personally-relevant.

In this study, a randomized, placebo-controlled between-subject design is adopted to investigate the effect of a single-dose of intranasally administered OT on approach-avoidance related motivational tendencies during the processing of a series of social and non-social, positively and negatively valenced stimuli. To obtain a behavioral measure of approach-avoidance tendencies, participants will be able to control the viewing time of the presented stimuli, by pressing 'up' or 'down' on a keyboard. During stimulus presentation neurophysiological recordings will be performed to obtain a neural measure of approach-avoidance motivational tendencies, based on electroencephalographic recordings (EEG: frontal alpha asymmetry). Also electrodermal recordings (skin conductance) will be collected to obtain assessments of sympathetically-driven autonomic arousal.

In accordance to the GAAO account, it is hypothesized that OT will reduce avoidance-related motivational tendencies (assessed behaviorally and using EEG), irrespective of sociality (i.e. similar effect towards social and non-social stimuli).

In accordance to prior research, skin conductance responses are hypothesized to reduce after OT, indicating reduced sympathetically-driven autonomic arousal. On the other hand, considering the implicated role of sympathetic arousal in orienting responses, OT might also facilitate an enhancement of skin conductance responses, i.e., being reflective of OT's role in enhancing salience toward emotionally-evocative stimuli.