Abstract
Background: Amnestic mild cognitive impairment (aMCI) has a high conversion risk to Alzheimer’s disease (AD). The aMCI patients may have only a memory deficit (single-domain-aMCI, sd-aMCI) or deficits in multiple cognitive domains (multiple-domain-aMCI, md-aMCI). However, differences in intrinsic brain activity between these two sub-types remain unclear.Method: Neuropsychological and resting-state functional magnetic resonance imaging (fMRI) data were acquired from 24 patients with sd-aMCI, 23 patients with md-aMCI, and 32 healthy controls (HCs). We used the fractional amplitude of low-frequency fluctuation (fALFF) to characterize the intensity of spontaneous brain activity. The analysis of covariance (ANCOVA) and post hoc tests was performed to determine the between-group differences in fALFF.Results: We found higher fALFF in left-sided superior-to-middle frontal gyri and middle-to-inferior temporal gyri in sd-aMCI compared to both the md-aMCI and HCs. Conversely, a lower fALFF was found in the left inferior parietal lobe in both the md-aMCI and sd-aMCI patients. The fALFF values in the left middle and inferior temporal gyri were correlated with cognitive performances.Conclusion: The gradual reduction in the left inferior parietal lobe from single to multiple domain aMCI suggest a functional inefficiency underlying cognitive impairment, while increased activity in the frontal and temporal gyri in sd-aMCI rather than md-aMCI might indicate functional compensation. This study indicates differential functional profiles in the sd-aMCI and md-aMCI, which may be helpful for the prediction of the future conversion of aMCI to AD.
Highlights
Alzheimer’s disease (AD) is a leading cause of dementia worldwide
Patients were diagnosed according to Petersen’s criteria (Petersen et al, 2001) and National Institute on Aging-Alzheimer’s Association criteria for MCI due to AD (American Psychiatric Association, 1994) according to the criteria: memory complaint; objective memory impairment; near-normal performances on general cognition and preserved daily life activities measured by Activity of Daily Living Scale (ADL); Clinical Dementia Rating (CDR) score of 0.5; failure to meet the criteria of dementia according to the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV; Wang et al, 2011); hippocampal atrophy measured by the Medial Temporal lobe Atrophy scale (MTA scale)
For the AVLT, mini-mental state examination (MMSE), MoCa, Boston naming test (BNT), trail making test (TMT)-A, and TMT-B, both the md-Amnestic mild cognitive impairment (aMCI) and sd-aMCI groups showed significant decreases compared to healthy controls (HCs) (p < 0.001)
Summary
Alzheimer’s disease (AD) is a leading cause of dementia worldwide. Once the clinical symptoms of dementia emerge, the brain atrophy has been irreversible, rendering the recognition of AD at the early stage an urgent prerequisite for effective intervention. Even though the aMCI diagnosis relies primarily on the presence of memory dysfunction, it is increasingly recognized that aMCI may represent a highly heterogeneous condition and impairments in other cognitive domains were often observed in aMCI patients (Brambati et al, 2009; Lenzi et al, 2011; Li and Zhang, 2015). The aMCI could be classified into single-domain-aMCI (sd-aMCI) and multiple-domain-aMCI (md-aMCI) sub-types (Brambati et al, 2009; Lenzi et al, 2011; Li and Zhang, 2015). Amnestic mild cognitive impairment (aMCI) has a high conversion risk to Alzheimer’s disease (AD). Differences in intrinsic brain activity between these two sub-types remain unclear
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