Experimenter’s Respiration Affects fNIRS Signals in Neonates Held in Cuddled Positions

As optical brain imaging technologies become increasingly portable and wear- able, their application is expanding across diverse contexts, populations, and more naturalistic experimental paradigms. However, these advances, along with novel testing conditions, may also introduce new challenges in ensuring data quality during acquisition. In this study, we investigated data quality issues encountered during high-density diffuse optical tomography (HD-DOT) measurements in neonates tested in a cuddled position. During quality assess- ment for a longitudinal project, we identified a signal component with distinct temporal and spectral features inconsistent with those expected for this age group. By examining the frequency characteristics of this component, its spatial prominence across the HD-DOT cap, and detailed video-based assessments of participant positioning, we identified a confounding factor stemming from the experimenter’s respiration and transmitted as a movement artefact to the HD-DOT headgear. We propose strategies to identify and remove this component, which could be adapted for other studies employing optical brain imaging technologies. Given the importance of flexible and comfortable testing positions in neonatal populations and the potential of wearable neuroimaging systems for enabling more naturalistic paradigms, detailed data assessment is essential to detect unexplored sources of noise and to ensure accurate interpretation of optical brain imaging data.