Differences in functional brain activation and hippocampal volume among amnestic mild cognitive impairment subtypes
Xin Li, Lu Zheng, Junying Zhang
1State Key Laboratory of Cognitive Neuroscience and Learning, Beijing Normal University, Beijing 100875, P. R. China. zhang_rzs@bnu.edu.cn.
Abstract:
Patients with amnestic mild cognitive impairment (aMCI) often display deficits in episodic memory. Amnestic MCI is now recognized as a prodromal form of Alzheimer's disease. Various aMCI clinical subtypes have been identified as ingle-domain (SD) or multi-domain (MD). The various subtypes represent heterogeneous syndrome indicating the probability of progression to AD, impaired cognitive domains and so on. To examine the characteristics of brain regions of aMCI subtypes is likely to be important for early diagnosis and prediction to AD. This study investigated brain functional activation and hippocampal atrophy during a visually complex scene encoding in 20 individuals with aMCI-SD, 14 individuals with aMCI-MD and 25 healthy controls. During the encoding task, aMCI-MD patients had reduced activation in right superior medial frontal, right inferior and middle temporal, right middle occipital and left inferior frontal regions compared to controls. The different active brain regions between aMCI-MD and aMCI-SD patients are the right middle occipital and left middle cingulum regions. The aMCI-MD group had significantly lower left hippocampus volumes compared to the aMCI-SD group and controls, but there was no difference between aMCI-SD patients and the control group in terms of left hippocampus atrophy. The findings provide evidence that aMCI may represent a heterogeneous group. The aMCI-MD patients displayed more severe hippocampcal atrophy and fMRI activation changes than aMCI-SD. The aMCIMD may represent a more advanced prodromal stage of AD.
Insights
Multi-domain amnestic mild cognitive impairment (aMCI-MD) shows greater brain changes and hippocampal atrophy than single-domain aMCI (aMCI-SD). aMCI-MD may indicate a more advanced prodromal stage of Alzheimer's disease.
Area of Science:
- Neuroscience
- Cognitive Neurology
- Medical Imaging
Background:
- Amnestic mild cognitive impairment (aMCI) is a precursor to Alzheimer's disease (AD).
- aMCI presents as heterogeneous subtypes, including single-domain (aMCI-SD) and multi-domain (aMCI-MD), impacting diagnostic and prognostic accuracy.
- Understanding subtype-specific brain alterations is crucial for early AD detection.
Purpose of the Study:
- To investigate differences in brain functional activation and hippocampal volume between aMCI-MD and aMCI-SD patients.
- To compare brain characteristics during a complex visual scene encoding task.
- To determine if aMCI subtypes represent distinct stages of AD prodrome.
Main Methods:
- Functional magnetic resonance imaging (fMRI) to assess brain activation during a visual encoding task.
- Voxel-based morphometry to evaluate hippocampal atrophy.
- Comparison of brain imaging data across 20 aMCI-SD patients, 14 aMCI-MD patients, and 25 healthy controls.
Main Results:
- aMCI-MD patients exhibited reduced activation in several brain regions, including the right superior medial frontal and left inferior frontal cortex, compared to controls.
- Distinct patterns of altered brain activation were observed between aMCI-MD and aMCI-SD patients (right middle occipital and left middle cingulum).
- aMCI-MD patients showed significantly greater left hippocampal atrophy than both aMCI-SD patients and controls.
Conclusions:
- aMCI subtypes exhibit distinct neurobiological profiles.
- aMCI-MD is associated with more pronounced functional brain changes and hippocampal atrophy, suggesting a more advanced stage of AD prodromal development.
- These findings support the heterogeneity of aMCI and highlight the potential of neuroimaging for differentiating disease progression.
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