Addressing Arbitrary Choices of Frequency Band of Interest in fNIRS Hyperscanning

Neuroimaging hyperscanning—the monitoring of brain activity of two or more persons simultaneously—has emerged as a popular tool to uncover the neural mechanisms of social interactions. The use of functional near-infrared spectroscopy (fNIRS)—a non-invasive, child-friendly technique tolerant of motion artifacts—has significantly advanced this line of research. Despite its popularity, the field has yet to agree on best practices for quantifying inter-brain connections (IBC) during social interactions, including the frequency of interest (FOI) for signal analysis. Consequently, past research findings have been inconsistent. In this study, we reviewed various methods used and their corresponding FOI results in previous fNIRS hyperscanning research focused on the topics of cooperation, collaboration and/or coordination. Additionally, we proposed a new methodology to quantify FOI that aimed to uncover the origin of synchronization between brains. We tested the proposed method on two independent fNIRS hyperscanning datasets involving different populations and social interactions, which are commonly reported in the literature. We offer a method for testing and adoption within the fNIRS community, aimed at eliminating arbitrary FOI selections and potentially enhancing the reproducibility of results in future fNIRS hyperscanning research.