Adaptive reconfiguration of prefrontal networks during prolonged cognitive interference: Evidence from fNIRS

In the era of information overload, understanding the brain's adaptive responses to prolonged cognitive tasks is critical. This study investigates the neural compensatory mechanisms that sustain cognitive performance under mental fatigue, offering insights into dynamic resource allocation and practical applications in high-demand settings. Twenty healthy participants performed a Stroop-based cognitive interference task while prefrontal hemodynamic activity was monitored using functional near-infrared spectroscopy (fNIRS). Subjective fatigue was assessed via the Multidimensional Fatigue Inventory (MFI-20), NASA Task Load Index (NASA-TLX), and Visual Analogue Scale (VAS). Behavioral performance (reaction time and accuracy) was recorded simultaneously. Neural activation was analyzed using a Generalized Linear Model (GLM), and functional connectivity alongside network topology metrics (global efficiency, clustering coefficient) were evaluated. Results show that subjective fatigue increased significantly post-task (MFI-20, p < 0.05), with progressive rise in VAS scores. Behaviorally, reaction times decreased while accuracy remained stable, indicating a speed-accuracy trade-off. fNIRS revealed marked activation changes in specific prefrontal regions (e.g., CH1, CH7), with overall activation shifting from positive to negative. This pattern may reflect time-dependent modulation of task-evoked activation and could be associated with multiple factors, including fatigue-related changes in engagement, habituation effects, or resource-related processes. In addition, fatigue accumulation was accompanied by increased functional connectivity between the frontal eye fields (FEF) and dorsolateral prefrontal cortex (DLPFC) (F = 4.61, p = 0.008), as well as between the frontopolar area (FPA) and DLPFC (F = 3.74, p = 0.020). Global efficiency (F = 0.169, p = 0.022) and clustering coefficient (F = 0.177, p = 0.008) also showed significant increases across task progression.Together, these findings may indicate time-dependent modulation of prefrontal network organization during prolonged cognitive interference tasks. Rather than reflecting a single mechanism, these changes could be associated with dynamic adjustments in functional coordination under sustained task demands. The present findings may provide preliminary neurophysiological evidence relevant to neuroergonomics, brain-computer interfaces, and cognitive workload management.