Cerebral white matter microstructure in superagers: A diffusion MRI study of a population over the age of 80 with youthful episodic memory

Abstract

AbstractBackgroundSuperagers are people over the age of 80 who possess the episodic memory function of a person 20‐30 years younger. We have recently identified the grey matter signature of this population, with preserved volume in episodic memory‐related areas and motor thalamus. Here we extend these observations by characterising superagers’ cerebral white matter microstructure using diffusion MR imaging.MethodA sample of 64 superagers (mean age 81.9 years ± 1.9 std, 59.4% women) and 55 age‐matched controls (mean age 82.4 years ± 1.9 std, 63.6% women) from the Vallecas Project cohort in Madrid, Spain, were selected according to their episodic memory score in the Free and Cued Selective Reminding Test. Superagers scored at or above the mean value of a 50‐56yo person, whereas controls scored within one standard deviation for their age. Differences across groups in two measures derived from DTI data were tested, comprising fractional anisotropy (FA), and mean diffusivity (MD). Voxelwise analyses were carried out using TBSS (Tract‐Based Spatial Statistics, [Smith 2006]), in FSL software.ResultSuperagers showed higher FA than controls in bilateral frontal tracts and the anterior thalamic radiation (p < 0.05, FWE‐corrected). Lower MD were found in superagers compared to controls in an extensive network comprising the forceps major and minor, superior and inferior longitudinal fasciculus, inferior fronto‐occipital fasciculus, anterior thalamic radiation, corticospinal tracts and cingulum bundle (p < 0.05, FWE‐corrected).ConclusionHigher FA and lower MD can be indicative of preserved white matter microstructure. Superagers exhibit higher FA in frontal tracts and lower MD across the main cerebral white matter tracts relative to healthy controls with normal‐memory‐for‐age. These results suggest an association between preservation of white matter microstructure and extraordinary memory function in old age.