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 similar to 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.