The effect of intranasal oxytocin on the neural process of child-related social signals on young mothers

Background: Over the past few decades, oxytocin (OT) has been identified as a neural hormone playing positive roles in parental bonding, sexual behaviours, and social affiliation behaviours. Additionally, OT has shown to be correlated with parental sensitivity, parenting contact, and parent-child synchrony, thus helping to strengthen the parent-child bonding. Therefore, the use of OT as an intervention of harsh and difficult parenting such as maternal depression or parent-child bonding disorders has attracted wide attention from academia and research. Objectives: The thesis study primarily aimed at investigating whether intranasal administration of OT affected the neurocognitive process in young mothers perceiving infant’s facial emotional stimuli via the Event-related Potentials (ERPs), i.e. a neural technique used to investigate brain functioning. Subsequently, the secondary objective was to examine whether the subjective perception of bonding in mothers got influenced by OT via two questionnaires. Data and methods: The thesis study was a sub-set of the project study conducted by University Hospital of Tampere (TAYS), from which two different types of data were extracted and analysed: the ERPs (three components: N170, EPN and LPP) and two modified questionnaires (i.e. Postpartum Questionnaire (PBQ) and Experiences of Close Relationship-Relationship Structure Questionnaire (ECR-RS)). The thesis study was conducted in a placebo-controlled, double-blind, within-subjects design with 52 participants. They were asked to visit one laboratory two times with a one-month interval in order to perform the ERP task and fill in two questionnaires. Using the ERP data for the primary objective, the N170 and posterior EPN components were analyzed with a 2 x 2 x 2 x 2 repeated-measures analysis of variance (ANOVA) with Face (Infant vs. Adult), Emotion (Happy vs. Sad/distressed), Condition (OT, vs. PL), and Hemisphere (left vs. right) as within-subjects factors. Likewise, the LPP data were analyzed with 2 x 2 x 2 ANOVA with the factors Age, Emotion and Condition. In contrast, the questionnaire data was analysed through a paired sample t-test to compare the results of the questionnaires between OT and placebo condition. Results and Discussion: When analyzing interactions among variables in all three ERP components, OT was not found to significantly affect the neurocognitive process in young mothers (p-values= 0.97, 0.13 and 0.46 for N170, EPN and LPP, respectively). Interestingly, then interaction Face x Condition in the N170 component was found to be marginally significant (F (1, 37) =3.30, effect size=0.08, p-value=0.07), indicating that there was a difference in the effect of OT on the social-emotional mothers’ perception. However, this effect was either faintly supported by the present analysis or very minute if the effect did exist. Besides, only in the N170 component, the main effect of Condition appeared significantly (F (1, 37) =15.11, effect size=0.16, p-value=0.01 ), which indicated the OT held larger negativity than placebo (-6.65±0.50µV and -6.34±0.49µV, respectively). Contrary to expectations, the results of two questionnaires yielded no significant difference in questionnaires’ scores of the mothers when receiving either OT or placebo (p-value=0.6, 0.82 and 0.34 for the PBQ, Avoidance, and Anxiety scores of ECR-RS, respectively). The study contributes to the current evidence of the pro-social effects of OT, which has shown to be inconsistent and incoherent. Therefore, successive studies with larger population could be conducted to increase the reliability of the results. Moreover, the effect of genetic factors and epigenetics should be also taken into account in further studies since literature evidence suggests individual variations in OT may contribute to OT responses