Prefrontal functional connectivity analysis of cognitive decline for early diagnosis of mild cognitive impairment: a functional near-infrared spectroscopy study

Abstract

Cognitive decline (CD) is a major symptom of mild cognitive impairment (MCI). Patients with MCI have an increased likelihood of developing Alzheimer's disease (AD). Although a cure for AD is currently lacking, medication therapies and/or daily training in the early stage can alleviate disease progression and improve patients' quality of life. Accordingly, investigating CD-related biomarkers via brain imaging devices is crucial for early diagnosis. In particular, "portable" brain imaging devices enable frequent diagnostic checks as a routine clinical tool, and therefore increase the possibility of early AD diagnosis. This study aimed to comprehensively investigate functional connectivity (FC) in the prefrontal cortex measured by a portable functional near-infrared spectroscopy (fNIRS) device during a working memory (WM) task known as the delayed matching to sample (DMTS) task. Differences in prefrontal FC between healthy control (HC) (n = 23) and CD groups (n = 23) were examined. Intra-group analysis (one-sample t-test) revealed significantly greater prefrontal FC, especially left-and inter-hemispheric FC, in the CD group than in the HC. These observations could be due to a compensatory mechanism of the prefrontal cortex caused by hippocampal degeneration. Inter-group analysis (unpaired two-sample t-test) revealed significant intergroup differences in left-and inter-hemispheric FC. These attributes may serve as a novel biomarker for early detection of MCI. In addition, our findings imply that portable fNIRS devices covering the prefrontal cortex may be useful for early diagnosis of MCI.

Functional Near-Infrared Spectroscopy and Its Clinical Application in the Field of Neuroscience: Advances and Future Directions

“…A recent systemic review including 36 articles over the past two decades suggests that patients with MCI and AD have impaired frontal and long-range connectivity in the resting state fMRI ( Yeung and Chan, 2020 ), which was also observed in a recent study ( Yoo and Hong, 2019 ). Task-related functional connectivity analysis suggests that the number and strength of prefrontal functional connections increased during a working memory task ( Yu et al, 2020 ) but left and inter-hemispheric connectivity during a verbal fluency test were lower ( Nguyen et al, 2019 ) in the patients with MCI compared to healthy controls. This could indicate the use of compensatory mechanisms in the prefrontal cortex as a result of impaired default connectivity in MCI patients.…”

Aerobic Exercise Mediates Neural Inefficiency Among Adolescents At Risk for Suicide

“…These researchers interpreted the higher cortical networking in the suicide risk group as a brain-based compensatory strategy for contending with depression-related performance degradation. In other studies, patients with mild cognitive impairment showed higher brain activation and greater cortical communications than participants in the general population, and, in these studies, the also explained their findings in terms of brain-based compensatory mechanisms for contending with cognitive decline (Jiang, 2005;Pijnenburg et al, 2004;Stern, 2009;Yu et al, 2020;Zheng et al, 2007). We addressed potential remediation for neural efficiency, as we observed lower EEG coherence (higher neural efficiency) among those high suicide risk adolescents who participated in a 9-week aerobic exercise program than among those who were in a no exercise group.…”

Frequency-Dependent Effects on Coordination and Prefrontal Hemodynamics During Finger Force Production Tasks

“…One-sample t -test was performed to check the consistency of intra-channel correlations for all participants. The number of significant functional connections (FC N ) was quantified based exclusively on the following criteria (Yu et al, 2020 ): (1) statistical significance at p ≤ 0.05 with the Bonferroni p -value correction method; and (2) high correlation coefficient, r ≥ 0.7 ( Figure 2 ). In addition, the FC N between channels located in the intra- and inter-hemispheres were counted separately.…”

“…In particular, fNIRS quantifies the oxygen-saturated hemoglobin (i.e., oxy-hemoglobin, O 2 Hb) and deoxygenated hemoglobin (i.e., deoxyhemoglobin, HHb) in the blood circulating to the prefrontal region. In addition, the observation of concurrent activations of different locations within the prefrontal region, the so-called functional connectivity (Murrough et al, 2016 ; Yu et al, 2020 ), may provide information about the interconnected neural activation for voluntary movement in the prefrontal region and its changes with the frequency changes of cyclic actions. Therefore, it is possible that the prefrontal circuitry is modulated by the frequency of cyclic actions.…”