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P4‐583: MICROSTRUCTURAL ALTERATIONS WITH OLDER AGE EVALUATED USING THE NODDI MODEL IN A LARGE GROUP OF COGNITIVELY UNIMPAIRED INDIVIDUALS
Author(s) -
VanDerwerker Nicholas B.,
Vogt Nicholas M.,
Asthana Sanjay,
Johnson Sterling C.,
Alexander Andrew L.,
Bendlin Barbara B.
Publication year - 2019
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2019.08.131
Subject(s) - white matter , diffusion mri , magnetic resonance imaging , medicine , correlation , audiology , psychology , population , bonferroni correction , fractional anisotropy , nuclear medicine , statistics , radiology , mathematics , geometry , environmental health
fluctuations in FC. An analytic approach known as dynamic functional connectivity, wherein fMRI data is divided into sequential time windows used to generate multiple FC networks per subject, enables characterization of the evolution of FC over time that may enable greater sensitivity to alterations in brain network organization in dementia than static FC.Methods: 113 fMRI scans (600 s length, TR1⁄4 1.2s) of participants with either subjective cognitive decline (SCD, self-perceived decline without psychometric impairment, n 1⁄4 35), mild cognitive impairment (MCI, n 1⁄4 33), or cognitively normal controls (n 1⁄4 45) were divided into 50 overlapping time windows 112 s long separated by 9.6 s intervals. FC was calculated within each window to generate multilayer dynamic functional connectivity network consisting of 50 sequential FC networks. Each layer of the dFC network was then partitioned into subnetworks, e.g. visual or motor, whose member ROIs are strongly interconnected. The functional flexibility of an ROI was then estimated by the percentage of time windows that an ROI switches subnetworks, and the mean flexibility for each subject was also calculated. Results: An ANCOVA comparing the mean flexibilities of the control, SCD, and MCI group with age, education level, sex, race, and ethnicity as covariates indicated a significant group difference (F 1⁄4 3.442, p 1⁄4 0.031), with the means (SD) of the control, SCD, andMCI groups at 0.1663 (0.0594), 0.1913 (0.0453), 0.1950 (0.0432). Mean flexibility correlated with the memory component of the CCI-20-S (r 1⁄4 0.242, p 1⁄4 0.012). Conclusions: Flexibility in patterns of FC increases in SCD and MCI patients and is associated with self reported decreases in memory.