TASK-EVOKED OXYGEN SUPPLY AND UTILIZATION DYNAMICS IN HUMAN MPFC DURING VIRTUAL SPATIAL NAVIGATION MEASURED WITH A HIGH-SENSITIVITY WEARABLE FNIRS

Portable, easy-to-use functional near-infrared spectroscopy (fNIRS) systems are becoming increasingly popular for studying cognition in naturalistic settings. Yet most available solutions either offer limited sensitivity or require complex, custom electronics, which limit accessibility. Here, we present an integrated, Bluetooth-enabled wearable fNIRS device, assembled entirely from off-the-shelf components that achieves a higher signal-to-noise ratio (>4 times) than commercial oximeters, enabling robust detection of transient, task-linked oxygenation responses. We validate the device across four functional benchmarks: (i) movement-evoked activity in primary motor cortex during finger motion, (ii) visual-cortex responses during changes in visual contrast, (iii) breath-hold and iv) blood occlusion test. Leveraging the improved sensitivity, we introduce a novel event-based metric, task-Evoked Instances of Differential Oxygen influx (tEIDO), to quantify brief oxygen supply and utilization transients aligned with behavioral events. Using this platform, we investigated the involvement of the medial prefrontal cortex in spatial memory during a virtual navigation paradigm. We collected data from 50 healthy adults for this study. During acquisition, deeper mPFC regions showed progressive spatial localization, with selective reactivation during retrieval. Notably, oxygen influx patterns were spatially localized to the hidden target location rather than non-target regions and were predictive of retrieval performance. These results demonstrate that a highly sensitive, portable fNIRS system can reliably capture behavior-induced cortical oxygen dynamics under naturalistic conditions, providing a portable neuroimaging tool for real-time monitoring of brain dynamics.