Born to sync: exploring inter-brain synchrony in mother-infant dyads during face-to-face Still-Face interactions. An EEG hyperscanning pilot study.

Previous studies in developmental science have shown that caregiver-infant dyads often display biobehavioural synchrony during their interactions. In this field, the Still-Face procedure (SFP) by Tronick has been widely employed to investigate how a dyad can repair a disrupted interaction and re-establish a connection. Recently, the advent of the hyperscanning technique has allowed to explore inter-brain synchrony (IBS) dynamics between caregivers and infants, however no study in the literature specifically focused on the IBS during the SFP. In our pilot study, we employed EEG hyperscanning to investigate IBS in 6 mother-infant dyads taking part in the SFP. We computed the Phase Locking Value (PLV), an index of phase synchrony, for the Play and Reunion episodes and explored variations across episodes by means of repeated-measure ANOVAs. Our results, although preliminary, showed a Play-to-Reunion decrease in IBS in theta and alpha frequency bands. In the theta frequency band, IBS was especially observed over central electrodes, in line with previous findings on joint attention in caregiver-infant dyads. In the alpha frequency band, we reported a trend of increased lateralization to the right, similarly to previous findings on stress-regulating functions in infants and on the lateralization of emotionality. In conclusion, our findings suggest that not only biobehavioural, but also inter-brain synchrony in mother-infant dyads might be negatively affected by experimentally induced interactive disruptions during face-to-face interactions. While further IBS analyses and the conjoint analysis of behavioural and neurophysiological synchrony measures are warranted to provide more robust results in the final sample, these preliminary findings are of great interest to researchers and clinicians in the field of developmental psychology and neuroscience. The knowledge derived from this study might find potential applications in the diagnosis and treatment of clinical developmental populations characterized by socio-emotional and socio-cognitive challenges, such as infants born preterm or with sensory deficits.