A Cost-Effective fNIRS System for Multisubject Multibrain Regions Hyperscanning

Functional near-infrared spectroscopy (fNIRS) has demonstrated exceptional ecological validity in revealing the neural coupling mechanisms between brains during real-world social cognitive interactions. However, the study of interpersonal brain synchronization (IBS) with more brain regions coverage during multisubject cognitive interactions remains a key challenge for future research. Current fNIRS systems face limitations in terms of ability to cover brain regions, scalability, cost, compatibility with multimodal brain imaging technologies, and wearability. These factors hinder the in-depth exploration of more subjects and more brain regions in hyperscanning research. To address this, we propose a multichannel configuration method based on time-division square wave analog lock-in operating mode (MC-TSAL), following an analysis of the shortcomings of fNIRS system developed using different lock-in operating modes. This method significantly enhances the cost-effectiveness of multichannel fNIRS system and its design advantages of low complexity and low data transmission volume provide better potential for wireless expansion. Furthermore, a system prototype TSAL-NIR16 based on this method was developed. Its hardware and software configuration, along with the audio plug-type dual splitters structure, make it suitable for more hyperscanning application scenarios. The system’s performance was evaluated through phantom experiments, and its accuracy in detecting hemodynamic responses was validated through forearm arterial occlusion (AO) experiments compared with the commercial device NIRScout. Finally, the system’s ability to explore dynamic IBS in hyperscanning applications was preliminarily validated through an adapted “Etch-a-Sketch” drawing game. The fNIRS system prototype proposed in this article, designed based on MC-TSAL demonstrated excellent performance, offering a cost-effective system development path for hyperscanning studies in complex cognitive interaction scenarios, with broad application prospects.