Different properties of the hemodynamic response and its relation to trait mental fatigue and proactive cognitive control

Introduction The Dual Mechanism of Control theory proposes that we use our cognitive control in a proactive and reactive mode. The proactive mode is used to optimize performance in more challenging tasks and is thought to be a more demanding activity. Trait mental fatigue is the overall disposition of mental fatigability and sensation of mental weariness and exhaustion. In the present study, we investigated the association between trait mental fatigue, proactive control, and different properties of the hemodynamic response in the frontal and parietal cortex of healthy adults.Method 30 healthy adults answered the Mental Fatigue Scale (MFS), performed the AX-Continuous Performance Task (AX-CPT), a test of proactive cognitive control which generates the proactive behavioral index (PBI), and underwent functional near-infrared spectroscopy (fNIRS) to measure functional activity in the frontal and parietal cortex while being tested on the AX-CPT.Result There was a Spearman's correlation ρ = -0.462 between MFS and the PBI, indicating an association between trait mental fatigue and a tendency to rely on reactive cognitive control. The exploratory analysis indicated that higher trait mental fatigue was associated with higher oxygenated hemoglobin concentrations (oxy-Hb) and total hemoglobin (tot-Hb) from the initial dip to up to the peak during reactive situations. This was observed bilaterally in the medial posterior partial (MPPC) cortex and the right lateral palatal cortex (LPC) for oxy-Hb. In contrast, for tot-Hb, this pattern was also observed in the left dorsolateral prefrontal cortex (DLPFC) and right anterior DLPFC, bilateral MPPC, right lateral PPC, and right parietal cortex. Individuals with a more reactive response type showed during proactive situations a higher concentration of oxy-Hb and tot-Hb in the right MPPC and the right LPPC for oxy-Hb for the latter part of the hemodynamic response.Discussion/conclusion Higher trait mental fatigue is associated with a tendency to favor reactive over proactive cognitive control in healthy adults. fNIRS imaging detected the involvement of several brain regions in trait mental fatigue. However, further research is needed to determine whether the hemodynamic response function could be linked to suboptimal neurovascular coupling.