Altered functional connectivity of prefrontal cortex in healthy elderly and Alzheimer's disease patient during a verbal fluency task: An fNIRS study

Deviations in activation patterns and functional connectivity have been observed in patients with major depressive disorder (MDD) with prefrontal hemodynamics of patients compared with healthy individuals. The graph-theoretical approach provides useful network metrics for evaluating functional connectivity. The evaluation of functional connectivity during a cognitive task can be used to explain the neurocognitive mechanism underlying the cognitive impairments caused by depression. Overall, 31 patients with MDD and 43 healthy individuals completed a verbal fluency task (VFT) while wearing a head-mounted functional near-infrared spectroscopy (fNIRS) devices. Hemodynamics and functional connectivity across eight prefrontal subregions in the two groups were analyzed and compared. We observed a reduction in prefrontal activation and weaker overall and interhemispheric subregion-wise correlations in the patient group compared with corresponding values in the control group. Moreover, efficiency, the network measure related to the effectiveness of information transfer, showed a significant between-group difference [t (71.64) = 3.66, corrected p < 0.001] along with a strong negative correlation with depression severity (rho = −0.30, p = 0.009). The patterns of prefrontal functional connectivity differed significantly between the patient and control groups during the VFT. Network measures can quantitatively characterize the reduction in functional connectivity caused by depression. The efficiency of the functional network may play an important role in the understanding of depressive symptoms.

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The Relationship between Neuropsychiatric Symptoms and Default-Mode Network Connectivity in Alzheimer’s Disease

Psychiatry Investigation ◽

10.30773/pi.2020.0009 ◽

2020 ◽

Vol 17 (7) ◽

pp. 662-666 ◽

Cited By ~ 1

Author(s):

Jung Suk Lee ◽

Jong Hun Kim ◽

Seon-Koo Lee

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Prefrontal Cortex ◽

Functional Connectivity ◽

Medial Prefrontal Cortex ◽

Neuropsychiatric Symptoms ◽

Neuropsychiatric Inventory ◽

Montreal Neurological Institute ◽

Default Mode ◽

The Relationship

Objective Neuropsychiatric symptoms of dementia are prevalent and extremely burdening for the patient and caregivers, but the underlying mechanism of these symptoms has not been investigated. This study aimed to investigate the relationship between neuropsychiatric symptoms and default-mode functional connectivity in Alzheimer’s disease.Methods Neuropsychiatric symptoms were assessed using the Neuropsychiatric Inventory. Functional magnetic resonance imaging was conducted on seventy patients with Alzheimer’s disease during rest. We conducted a seed-based functional connectivity analysis to identify anterior and posterior default-mode networks (DMN). Seeds were the medial prefrontal cortex (Montreal Neurological Institute 12, 51, 36; seed radius=3 mm) for the anterior DMN and the precuneus (Montreal Neurological Institute -6, -63, 27; seed radius=3 mm) for the posterior DMN We then correlated the scores on neuropsychiatric inventory syndromes (apathy, hyperactivity, affective, and psychosis syndrome) with maps of connectivity in the default-mode network.Results There was a significant correlation between decreased connectivity in the medial prefrontal cortex of the anterior defaultmode network and hyperactivity (agitation, irritability, aberrant motor behavior, euphoria, and disinhibition) syndrome (p<0.05, family wise error cluster-level corrected).Conclusion Our study demonstrated that hyperactivity syndrome is related to hypoconnected default-mode network in Alzheimer’s disease. This finding suggests that specific network alterations are associated with certain neuropsychiatric syndromes.

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