Functional connectivity and cerebral cortex activation during the resting state and verbal fluency tasks for patients with mild cognitive impairment, Lewy body dementia, and Alzheimer's disease: A multi-channel fNIRS study

Objective: To explore changes in cerebral cortex activation and functional connectivity during resting-state and verbal fluency tasks in patients with different types of dementia. Methods: We recorded oxygenated hemoglobin concentration (HbO) signals detected by functional near-infrared spectroscopy (fNIRS) from the prefrontal cortex, partial parietal cortex, and cortex of the temporal lobe in four groups of participants: mild cognitive impairment (MCI), Lewy body dementia (LBD), Alzheimer's disease (AD), and cognitively normal (CN). Results: The study recruited 120 older adults with MCI (n = 30), LBD (n = 28), AD (n = 30), or CN (n = 32). The mean functional connectivity of the frontal and temporal lobe in resting state was significantly less in the AD (0.19 f 0.11) group than in the MCI (0.23 f 0.11), LBD (0.29 f 0.12), and CN (0.40 f 0.11) groups (p < 0.001). Further, the mean HbO concentrations in the brain regions and channels were significantly lower in the AD group than in the LBD and MCI groups (p < 0.001). Cognitive levels correlated significantly with the mean HbO concentrations in the resting state and verbal fluency task conditions. Conclusion: The fNIRS HbO signals significantly differed in the cerebral cortex regions in participants with different types of dementia. These findings suggest that fNIRS can effectively enhance the differential diagnosis and assessment of dementia.