Abstract
The present study aimed to investigate changes in structural gray matter (GM) volume and functional amplitude of spontaneous low-frequency oscillations (LFO) and functional connectivity density in patients with subcortical vascular mild cognitive impairment (svMCI). Structural MRI and resting-sate functional MRI data were collected from 26 svMCI patients and 28 age- and gender-matched healthy controls. Structurally, widespread GM atrophy was found in the svMCI patients that resided primarily in frontal (e.g., the superior and middle frontal gyri and medial prefrontal cortex) and temporal (the superior and inferior temporal gyri) brain regions as well as several subcortical brain sites (e.g., the thalamus and the caudate). Functionally, svMCI-related changes were predominantly found in the default mode network (DMN). Compared with the healthy controls, the svMCI patients exhibited decreased LFO amplitudes in the anterior part of the DMN (e.g., the medial prefrontal cortex), whereas increased LFO amplitudes in the posterior part of the DMN (e.g., the posterior cingulate/precuneus). As for functional connectivity density, the DMN regions (e.g., the posterior cingulate/precuneus, the medial prefrontal cortex and the middle temporal gyrus) consistently exhibited decreased functional connectivity. Finally, the overall patterns of functional alterations in LFO amplitudes and functional connectivity density remained little changed after controlling for structural GM volume losses, which suggests that functional abnormalities can be only partly explained by morphological GM volume changes. Together, our results indicate that svMCI patients exhibit widespread abnormalities in both structural GM volume and functional intrinsic brain activity, which have important implications in understanding the pathophysiological mechanism of svMCI.
Highlights
Mild cognitive impairment (MCI) refers to a transitional state between normal aging and dementia and is characterized by various symptom clusters
We investigated subcortical vascular MCI (svMCI)-related alterations in both functional spontaneous low-frequency oscillations (LFO) and the structural gray matter (GM) volume by combining resting-state fMRI and structural MRI techniques
We found that compared with HC, the svMCI patients exhibited a functional decrease in the amplitude of spontaneous LFO, primarily in the anterior part of the default mode network (DMN), whereas the amplitude was increased in the posterior part of the DMN
Summary
Mild cognitive impairment (MCI) refers to a transitional state between normal aging and dementia and is characterized by various symptom clusters. As a clinically heterogeneous syndrome, MCI can be classified into subtypes of amnestic and non-amnestic phenotypes, both of which can be further subdivided into two groups that exhibit cognitive deficits in single and multiple functional domains [1,2,3,4]. Numerous previous studies have primarily focused on amnestic MCI (aMCI), due to the relatively high incidence and straightforward clinical diagnosis of this type of MCI [5,6,7,8]. The non-amnestic MCI, the subcortical vascular MCI (svMCI) subtype, has begun to attract attention [9,10,11,12]. Recent evidence suggests that svMCI is potentially reversible [17,18]; characterizing the structural and functional brain abnormalities in the atypical population with svMCI can provide insights into understanding the pathophysiological mechanism of svMCI
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