A Cost-Effective Instrument of Distributed Functional Near-Infrared Spectroscopy for Hyperscanning Real-World Interactions

With the aim of hyperscanning real-world interactions using functional near-infrared spectroscopy (fNIRS) technology, a distributed wearable multimodule system is implemented in this study, enabling synchronous measurement of multiple subjects, wireless host–slave connections, and lower power consumption. In order to achieve an integrated characteristic of miniaturization, movement freedom, high cost-effectiveness, and hemodynamics profiling, the system is structured as a network of distributed fibreless optode modules, with each equipped with ten dual-wavelength light emitting diodes and four monolithic silicon photodiodes with an on-chip transimpedance amplifier. On-line digital lock-in detection based on a multiperiodic reference-weighted counting algorithm is performed in each slave to separate the signals from the different source–detector combinations as well as the wavelengths. Phantom and breath-holding experiments are designed to assess the fundamental performances of the implemented system, and validate the good raw signal quality with the static measurement fluctuation of
${< }2{\%}$
, dynamic optical range of
${>}72$
dB, and variation coefficient of
${\sim }5.39$
%, as ten channels work simultaneously, as well as the feasible sensitivity for detecting task-evoked activation. Finally, the dynamic interbrain synchrony is explored by simultaneously measuring the hemodynamic responses of two subjects while they played a cooperation game. This preliminary task-oriented experiment suggests that the proposed system has the capability of distilling the interbrain activation patterns with acceptable temporal resolution and bears high potential toward fNIRS-based social neuroimaging in the real world.