Abstract
The current study compared attention profiles and functional connectivity of frontal regions in patients with early-stage subcortical ischemic vascular disease (SIVD) and Alzheimer’s disease (AD). Twenty patients with SIVD, 32 patients with AD, and 23 subjects with normal cognition (NC) received cognition and resting-state functional MRI (rs-fMRI) evaluations. The Cognitive Abilities Screening Instrument (CASI) was used to assess global cognition, and simple attention, processing speed, divided attention, and vigilance/sustained attention were evaluated using the Digit Span Forward, Trail Making Test, Symbol Digit Modality Test, and Conners Continuous Performance Test, respectively. Voxel-based regional homogeneity (ReHo) derived from rs-fMRI data was analyzed to identify significant clusters, which were further correlated with attention profiles. Although the patients with SIVD and AD had comparable global cognitive ability, those with SIVD exhibited worse divided attention and vigilance/sustained attention than those with AD. Compared with the NC group, the patients with SIVD exhibited decreased ReHo within the right middle frontal gyrus (MFG) and left anterior cingulate gyrus (ACG), whereas the patients with AD exhibited increased ReHo within the right orbital part of frontal regions. Correlations between these three clusters with attention exhibited distinct patterns according to the dementia subtype, as did attention indices with significance in predicting global cognition. In summary, our study suggested that worse attention performance was associated with functional disconnection within the frontal regions among patients with SIVD than in those with AD. Frontal functional disconnection may underlie the pathogenesis responsible for defective divided attention, vigilance/sustained attention, and notable within-group variations identified in SIVD.
Highlights
Alzheimer’s disease (AD) and vascular dementia (VaD) have been reported to be the first and second most prevalent types of dementia, accounting for approximately 70 and 17% of all cases of dementia, respectively (Plassman et al, 2007)
There were no significant differences in age, education level, symptom duration, gender, handedness, dementia severity, and global cognition score between the patients with subcortical ischemic vascular disease (SIVD) and AD (p = 0.07–0.873)
The current study indicates that patients with early-stage SIVD and AD exhibit distinct patterns in both attention performance and frontal functional connectivity
Summary
Alzheimer’s disease (AD) and vascular dementia (VaD) have been reported to be the first and second most prevalent types of dementia, accounting for approximately 70 and 17% of all cases of dementia, respectively (Plassman et al, 2007). As VaD covers a wide spectrum of pathological changes including ischemia and micro/macrohemorrhage in various locations, SIVD provides an opportunity to explore the impact from vascular burden in the context of pathological and regional constraints (Kalaria, 2016; Dichgans and Leys, 2017). Patients with SIVD might be expected to suffer from a greater extent of white matter damage than those with AD; both types of dementia exhibit cerebral fiber disconnection to a certain degree to cause cognitive deficits (Absher and Benson, 1993). The myelin damage expected in patients with SIVD is diffuse, previous structural MRI studies have highlighted the role of white matter integrity within the frontal regions. Studies investigating attention have proven this concept by highlighting the early emergence of attention deficits and the cognitive impact among demented patients (Silveri et al, 2007; McGuinness et al, 2010; Neufang et al, 2011)
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