Development of an fNIRS-Based Neurofeedback System to Modulate Prefrontal Asymmetry

Functional near-infrared spectroscopy (fNIRS) is promising for neurofeedback (NF) applications and warrants further investigation. In this study, we developed an fNIRS-based NF system to modulate the hemodynamic asymmetry of the prefrontal cortex, which may help improve performance under pressure. The system was designed as a compact fNIRS system with two channels located in the prefrontal cortex and controlled using a smartphone. It calculates the dynamic laterality index (LI), indicating frontal asymmetry (a positive LI value when the left side is dominant), which is transformed into a white noise volume mixed with the music stimuli the participant listens to as feedback information. As the LI increases in the positive direction, the volume of the white noise reduces, making the music clearer. With this as the objective, the participants aimed to achieve a left-dominant state in the prefrontal cortex. We evaluated the NF system using a double-masked crossover design with eight participants. Analysis comparing the average LI in the NF and placebo conditions showed that the LI in the NF condition was significantly higher than that in the placebo condition. This finding demonstrates the feasibility of our NF system in modulating prefrontal asymmetry.