Infant brain responses to live face-to-face interaction with their mothers: Combining functional near-infrared spectroscopy (fNIRS) with a modified still-face paradigm

Abstract Background Non-invasive imaging techniques, such as fNIRS, allow us to shed light on the neural correlates of infant’s social-emotional development within the context of parent-infant interaction. On a behavioral level, numerous studies have investigated parent-infant interaction employing the still-face paradigm and found that the primary caregiver(s), often the mother, is an important coregulator of the infant’s physiological and behavioral stress response. However, limited information is available on how the infant’s brain reacts to the maternal cues during real-life interaction. Methods Therefore, the main aim of the current study was to design a fNIRS paradigm to study live mother-infant interaction and to explore the neural correlates of infant affect regulation during real-life dyadic interaction. To this end, a modified still-face paradigm was designed, which consists of live face-to-face mother-infant, and stranger-infant, interaction episodes, including stressful, “still-face” and non-stressful, “happy-face” interaction blocks, combined with infant fNIRS imaging. Results Hemodynamic brain responses were collected in n = 10 (6 females, mean age 230.2 ± 17.5 days), typically developing infants using the Hitachi ETG-4000 continuous-wave system (22 channels spanning the frontal cortex; 10 Hz system sampling frequency). Infants with usable data (n = 7) showed negative activations, indicated by a decrease in oxygenated hemoglobin, over the middle frontal gyrus in response to happy-face (reunion) interaction with their mothers compared to a female stranger; suggesting deactivation of brain regions associated with affect regulation. We also explored correlations between infant brain responses to maternal interaction and infant characteristics (temperament) as well as experiential/environmental factors (mothers’ self-reported depression symptoms). Conclusions Although the current results are very preliminary, they overall suggest that live design in infant populations is doable and offers unique opportunities to study the neural mechanisms underlying early caregiver(s)-child interaction in a more naturalistic context. Restrictions, and implications, of the methodology are critically discussed.