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Social cognition skills and socioemotional development are compromised in children growing up in low SES contexts, however, the mechanisms underlying this association remain unknown. Exposure to psychosocial risk factors early in life alters the child's social milieu and in turn, could lead to atypical processing of social stimuli. In this study, we used functional Near Infrared Spectroscopy (fNIRS) to measure cortical responses to a social discrimination task in children raised in a low-resource setting at 6, 24, and 36 months. In addition, we assessed the relation between cortical responses to social and non-social information with psychosocial risk factors assessed using the Childhood Psychosocial Adversity Scale (CPAS). In line with previous findings, we observed specialization to social stimuli in cortical regions in all age groups. In addition, we found that risk factors were associated with social discrimination at 24 months (intimate partner violence and verbal abuse and family conflict) and 36 months (verbal abuse and family conflict and maternal depression) but not at 6 months. Overall, the results show that exposure to psychosocial adversity has more impact on social information processing in toddlerhood than earlier in infancy.

Funder: H2020 European Research Council; doi: http://dx.doi.org/10.13039/100010663, Funder: Research Foundation Flanders, Funder: Universiteit Gent; doi: http://dx.doi.org/10.13039/501100004385, Funder: Marguerite-Marie Delacroix, Funder: Autistica; doi: http://dx.doi.org/10.13039/100011706, Funder: Riksbankens Jubileumsfond; doi: http://dx.doi.org/10.13039/501100004472; Grant(s): NHS14-1802:1, Funder: K.F. Hein Fonds, Funder: Scott Family Junior Research Fellowship, Autism is frequently associated with difficulties with top-down attentional control, which impact on individuals’ mental health and quality of life. The developmental processes involved in these attentional difficulties are not well understood. Using a data-driven approach, 2 samples (N = 294 and 412) of infants at elevated and typical likelihood of autism were grouped according to profiles of parent report of attention at 10, 15 and 25 months. In contrast to the normative profile of increases in attentional control scores between infancy and toddlerhood, a minority (7–9%) showed plateauing attentional control scores between 10 and 25 months. Consistent with pre-registered hypotheses, plateaued growth of attentional control was associated with elevated autism and ADHD traits, and lower adaptive functioning at age 3 years.

Despite the importance of our ability to interact and communicate with others, the early development of the social brain network remains poorly understood. We examined brain activity in 12- to 14-month-old infants while they were interacting live with an adult in two different naturalistic social scenarios (i.e., reading a picture book versus singing nursery rhymes with gestures), as compared to baseline (i.e., showing infants a toy without eye contact or speech). We used functional near-infrared spectroscopy (fNIRS) recorded over the right temporal lobe of infants to assess the role of the superior temporal sulcus - temporoparietal junction (STS-TPJ) region during naturalistic social interactions. We observed increased cortical activation in the STS-TPJ region to live social stimuli in both socially engaging conditions compared to baseline during real life interaction, with greater activation evident for the joint attention (reading book) condition relative to the social nursery rhymes. These results supported the view that the STS-TPJ region, engaged in the cortical social brain network, is already specialized in infants for processing social signals and is sensitive to communicative situations. This study also highlighted the potential of fNIRS for studying brain function in infants entering toddlerhood during live social interaction.

Brain and nervous system development in human infants during the first 1000 days (conception to two years of age) is critical, and compromised development during this time (such as from under nutrition or poverty) can have life-long effects on physical growth and cognitive function. Cortical mapping of cognitive function during infancy is poorly understood in resource-poor settings due to the lack of transportable and low-cost neuroimaging methods. Having established a signature cortical response to social versus non-social visual and auditory stimuli in infants from 4 to 6 months of age in the UK, here we apply this functional Near Infrared Spectroscopy (fNIRS) paradigm to investigate social responses in infants from the first postnatal days to the second year of life in two contrasting environments: rural Gambian and urban UK. Results reveal robust, localized, socially selective brain responses from 9 to 24 months of life to both the visual and auditory stimuli. In contrast at 0–2 months of age infants exhibit non-social auditory selectivity, an effect that persists until 4–8 months when we observe a transition to greater social stimulus selectivity. These findings reveal a robust developmental curve of cortical specialisation over the first two years of life. Keywords: fNIRS, Infancy, Low- and middle-income countries, Nutrition, Poverty, Social cognition

Social touch is ubiquitous in caregiver-infant interactions. Research on animal models and preterm human infants has shown that touch is critical for a young organism’s physical and psychological growth. However, the role that social interaction through touch plays in the development of typically developing human infants is poorly understood. The research presented in this thesis investigated neural specialization for social touch and the mechanisms through which social touch might promote early development. I focus on a particular type of touch, slow velocity stroking, shown to activate a particular type of skin fibers in human adults, the CT-fibers, and to elicit affective responses (henceforth affective touch). Research presented here investigated cortical activation and autonomic responses to affective touch, during the first year of life. Firstly, in experiments 1 through 4 functional Near Infrared Spectroscopy (fNIRS) was employed to measure haemodynamic responses to affective and non-affective touch over inferior frontal and temporal cortices. Experiments 1, 2 and 3 used three different non-affective stimuli and revealed that specialization to affective touch in key nodes of the social brain has not developed yet in 5 to 7-months-old infants. Results from Experiment 4 suggest that this specialization emerges near the end of the first year of life (10-montholds). Secondly, in experiments 5 and 6 heart rate changes to affective and nonaffective touch were measured in three different age-groups (2, 7 and 9-monthold). Results revealed that infants in neither group displayed differential responses to the touch stimuli. Further, experiment 5 explored whether affective touch modulates visual attention but an effect was not found. Taken together these findings showed that preferential processing of affective touch is not evident during early development, at least when investigating neural and autonomic responses. In all my studies, I strived to present tactile stimuli in the absence of other social cues, thus ensuring that any effects would have been specific to touch. In the final discussion I suggest that the lack of context might have prevented infants from identifying affective touch. I also discuss the possibility that other forms of inter-personal touch, and not CT-targeted touch, may be critical in early human development, and should be investigated in future research.