Final Report Summary - INFANT NIRS (Frontal Asymmetry as an Endophenotypic Marker of Differential Susceptibility to Parenting in Infancy: A Functional NIRS Study) Infants’ social-cognitive skills develop within the parent-infant relationship. Differences between parents in the way they interact with their infant may have important consequences for infants’ social-cognitive development. Moreover, due to their genetic make-up, some individuals may be more affected by their social environment than others. Indeed, genes that may convey this differential susceptibility have been identified. However, the analysis an use of genetic material is time-consuming, expensive, and surrounded by ethical concerns. Susceptibility may also not be conveyed by a single gene, but rather by many. Obtaining an endophenotype for susceptibility would therefore be worthwhile. Frontal asymmetry (differences in activity of the left and right frontal cortex) may be such an endophenotype. Because it can be measured easily, relatively cheaply, and non-invasively, frontal asymmetry may offer considerable advantages over genetic measures as a differential susceptibility marker. The project investigates frontal asymmetry as an endophenotype for differential susceptibility to effects of maternal sensitivity on infant social cognition. Because infant cognitive development is tightly intertwined with brain development we investigate effects of sensitivity on the neural underpinnings of socio-cognitive development, using fNIRS to image brain activity. We focus on two processes: activation of the mirror neuron system and neural processing of motherese. The project provides important insights into the neural mechanisms underlying differential susceptibility, highly relevant for our understanding of the processes leading to children’s successful or aberrant development. Insights gained from the study may also inform future studies searching for ways to enhance susceptibilityin individually tailored parenting support and interventions.Specifically, we have tested: -mothers' sensitivity to their infants' behavior by collecting behavioral data during a free-play and a toy-interaction session and -frontal asymmetries in infants' neurophysiological responses to speech spoken with happy vs. angry prosody We then proceeded to correlate these measures.A total of 43 mother-infant pairs participated in the study. Complete datasets (i.e. all measurements are of sufficient quality) are available for 22 pairs.Analyses evaluating the primary hypothesis that infants’ baseline frontal asymmetry would moderate the effect of maternal behavior on infants’ neural responses to infant directed speech show that infants whose mothers show less intrusive (more positive) behavior during play have a larger positivity in their ERPs in response to happy compared to angry words, likely reflecting greater resource allocation to happy than angry prosody. This result is in accordance with our expectations. However, there was no evidence for moderation of this effect by infants’ frontal asymmetry. Thus these results are not in accordance with differential susceptibility theory.
