Abstract
Purpose
To describe structural network differences in individuals with mild cognitive impairment (MCI) with high versus low executive abilities, as reflected by measures of white matter connectivity using diffusion tensor imaging (DTI).
Materials and methods
This was a retrospective, cross-sectional study. Of the 128 participants from the Alzheimer’s Disease Neuroimaging Initiative database who had both a DTI scan as well as a diagnosis of MCI, we used an executive function score to classify the top 15 scoring patients as high executive ability, and the bottom-scoring 16 patients as low executive ability. Using a regions-of-interest-based analysis, we constructed networks and calculated graph theory measures on the constructed networks. We used automated tractography in order to compare differences in major white matter tracts.
Results
The high executive ability group yielded greater network size, density and clustering coefficient. The high executive ability group reflected greater fractional anisotropy bilaterally in the inferior and superior longitudinal fasciculi.
Conclusions
The network measures of the high executive ability group demonstrated greater white matter integrity. This suggests that white matter reserve may confer greater protection of executive abilities. Loss of this reserve may lead to greater impairment in the progression to Alzheimer’s disease dementia.
Key Points
• The MCI high executive ability group yielded a larger network.
• The MCI high executive ability group had greater FA in numerous tracts.
• White matter reserve may confer greater protection of executive abilities.
• Loss of executive reserve may lead to greater impairment in AD dementia.
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Abbreviations
- AD:
-
Alzheimer’s Disease
- ADNI:
-
Alzheimer’s Disease Neuroimaging Initiative
- DTI:
-
Diffusion tensor imaging
- EF:
-
Executive function
- FA:
-
Fractional anisotropy
- MCI:
-
Mild cognitive impairment
- MCI-highEF:
-
Individuals with mild cognitive impairment with high executive abilities
- MCI-lowEF:
-
Individuals with cognitive impairment with low executive abilities
- MMSE:
-
Mini-Mental Status Examination
- MRI:
-
Magnetic resonance imaging
- PET:
-
Positron emission tomography
- RD:
-
Radial diffusivity
- ROI:
-
Region of interest
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Guarantor
The scientific guarantor of this publication is Ron Killiany, PhD.
Conflict of interest
The conflicts of interest are as follows: Dr. Budson has been an investigator for clinical trials for the following companies: AstraZenica, Hoffmann-La Roche, Eli Lily, FORUM Pharmaceuticals, and Neuronetrix. Dr. Moss serves as a consultant for Pfizer, Inc. Dr. Killiany is funded on two research grants from Pfizer, Inc. Dr. Mian is a shareholder of Boston Imaging Core Lab.
Funding
Data collection and sharing for this project was funded by the Alzheimer's Disease Neuroimaging Initiative (ADNI) (National Institutes of Health Grant U01 AG024904) and DOD ADNI (Department of Defense award number W81XWH-12-2-0012). ADNI is funded by the National Institute on Aging, the National Institute of Biomedical Imaging and Bioengineering, and through generous contributions from the following: AbbVie, Alzheimer’s Association; Alzheimer’s Drug Discovery Foundation; Araclon Biotech; BioClinica, Inc.; Biogen; Bristol-Myers Squibb Company; CereSpir, Inc.; Eisai Inc.; Elan Pharmaceuticals, Inc.; Eli Lilly and Company; EuroImmun; F. Hoffmann-La Roche Ltd and its affiliated company Genentech, Inc.; Fujirebio; GE Healthcare; IXICO Ltd.; Janssen Alzheimer Immunotherapy Research & Development, LLC.; Johnson & Johnson Pharmaceutical Research & Development LLC.; Lumosity; Lundbeck; Merck & Co., Inc.; Meso Scale Diagnostics, LLC.; NeuroRx Research; Neurotrack Technologies; Novartis Pharmaceuticals Corporation; Pfizer Inc.; Piramal Imaging; Servier; Takeda Pharmaceutical Company; and Transition Therapeutics. The Canadian Institutes of Health Research is providing funds to support ADNI clinical sites in Canada. Private sector contributions are facilitated by the Foundation for the National Institutes of Health (www.fnih.org). The grantee organisation is the Northern California Institute for Research and Education, and the study is coordinated by the Alzheimer's Disease Cooperative Study at the University of California, San Diego. ADNI data are disseminated by the Laboratory for Neuro Imaging at the University of Southern California.
Statistics and biometry
Danielle Farrar, MA performed the statistical analysis for this paper, with input from Dr. Ronald J. Killiany.
Informed consent
Written informed consent was obtained from all subjects (patients) in this study.
Ethical approval
Institutional Review Board approval was obtained.
Study subjects or cohorts overlap
This study was performed using data from the Alzheimer’s Disease Neuroimaging Initiative. Other studies published utilizing this dataset can be found at http://www.adni-info.org/Scientists/ADNIScientistsHome/ADNIPublications.html
Methodology
• retrospective
• cross-sectional study
• multicentre study
Additional information
Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database (adni.loni.usc.edu). As such the investigators within the ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report. A complete listing of ADNI investigators can be found at: http://adni.loni.usc.edu/wp-content/uploads/how_to_apply/ADNI_Acknowledgement_List.pdf
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Farrar, D.C., Mian, A.Z., Budson, A.E. et al. Retained executive abilities in mild cognitive impairment are associated with increased white matter network connectivity. Eur Radiol 28, 340–347 (2018). https://doi.org/10.1007/s00330-017-4951-4
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DOI: https://doi.org/10.1007/s00330-017-4951-4