The BRIGHT Project Team, | bioRxiv Science

bioRxiv2025

Effect of sleep stages on patterns of fNIRS hemodynamic response to auditory paradigms in one-month-old Gambian and UK infants

SignificanceFunctional near-infrared spectroscopy (fNIRS) has advanced our understanding of early brain development, especially infant responses to social and auditory stimuli. Unlike older children and adults, very young infants are often assessed during natural sleep to reduce movement and ensure sufficient data quality. Yet the impact of sleep stage on fNIRS signals and how it might affect interpretations of early brain activation patterns remains unclear. AimThis study investigates the effect of sleep stages on fNIRS-measured hemodynamic responses to two auditory paradigms across different global populations of one-month-old infants. ApproachIn total, 46 Gambian and 40 UK infants in quiet or active sleep were tested using (1) social selectivity and (2) a habituation and novelty detection paradigms. ResultsIn the UK cohort, active sleep was associated with a stronger initial response and greater habituation compared to quiet sleep. In contrast, Gambian infants in quiet sleep showed more widespread activation and evidence of habituation, while infants in active sleep showed no habituation. No sleep stage effects were observed for response in the social selectivity paradigm in either group. ConclusionsDifferent effects of sleep stages were observed across the two cohorts and paradigms and should be carefully considered in neuroimaging studies.

neuroscience↗

bioRxiv2025

Functional specialisation across the first five years of life: a longitudinal characterisation of social perception with fNIRS

Research in typically developing infants has shown robust and consistent brain activation to social versus non-social visual and auditory stimuli in a network of brain regions, including the inferior frontal, anterior temporal and posterior superior temporal cortex. However, large-scale, longitudinal neuroimaging studies across early childhood, particularly in low- and middle-income countries are rare, yet important, given that they offer a powerful means of capturing within-person changes in neurodevelopment and identifying targets for intervention and support. Here we investigated brain responses to social perception longitudinally across the first five years of life of participants in The Gambia with functional near-infrared spectroscopy (fNIRS) within the Brain Imaging for Global Health (BRIGHT) Project. We found that social visual stimuli elicited a selective right posterior temporal response across all six age points studied here (5, 8, 12, 18, 24 months and 3-5 years of age), with concurrent selective left responses at four of the six time points (5, 8, 18 months and 3-5 years of age). Inferior frontal regions showed brain activation at multiple ages, with the youngest (5 months) and oldest (24 months to 3-5 years) time points evidencing more widespread frontal social visual responses. Conversely, auditory social stimuli elicited a significantly stronger and more prolonged response than auditory non-social stimuli across all six age points from 5 months to 3-5 years across a range of frontal and temporal areas. Finally, from individual infant trajectories of brain activation, we identified different profiles of age-dependent specialisation to auditory social stimuli, with some specialising earlier than others. Future work could take advantage of such profiles to investigate the effects of adversity and resilience factors on neurodevelopment.

neuroscience↗