Abstract
Brain and nervous system development in human infants during the first 1000days (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.
Highlights
Infants in resource-poor settings may be frequently exposed to a range of social, environmental, nutritional and pathological insults
Responses at 9 – 13 and 18 – 24 months were less robust than at 4 – 8 and 12 – 16 months of age due to the sub-optimal headgear placement (this may have contributed to the diminished response seen in the time course of Cohort 3 (18 – 24 months) in Figure 5 as coverage may not have reached the area of peak activation for this age group)
To our knowledge this research in The Gambia is the first neuroimaging study to investigate cortical specialization to social cues across such a wide span of early development, with participants ranging in age from newborn to toddlerhood
Summary
Infants in resource-poor settings may be frequently exposed to a range of social, environmental, nutritional and pathological insults. According to a recent study, one third of children in developing countries fail to reach their developmental milestones in cognitive and/or socio-emotional growth, with the largest number of affected children in sub- Saharan Africa (McCoy et al, 2016). This means that over 80 million children in low and middle income countries (LMICs) fail to develop a core set of age-appropriate skills that allow them to maintain attention, understand and follow simple directions, communicate and cooperate with others, control aggression, and solve complex problems. Investigation of the developing brain in rural field settings has been broadly limited to behavioural assessments (Georgieff, 2007; Sabanathan et al, 2015)
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