Uncinate fasciculus microstructure and verbal episodic memory in amyotrophic lateral sclerosis: a diffusion tensor imaging and neuropsychological study

The present study evaluates the integrity of uncinate fasciculus (UF) and the association between UF microstructure and verbal episodic memory (as one of the cognitive functions linked to UF) in non-demented patients with amyotrophic lateral sclerosis (ALS) using diffusion tensor imaging (DTI). We studied 21 patients with ALS and 11 healthy, demographically-comparable volunteers. Fractional anisotropy, apparent diffusion coefficient, axial and radial diffusivity were the DTI metrics examined. Episodic memory was evaluated with Babcock Story Recall Test and Rey Auditory Verbal Learning Test (RAVLT) for patients; measures of immediate and delayed recall and retention for both tests and sum of words recalled through five learning trials for RAVLT were considered. Patients with ALS showed significant bilateral reduction of axial diffusivity in the UF as compared to controls. Furthermore, there were several significant relations between various DTI metrics (mostly in left hemisphere) and memory measures (specifically for the RAVLT). UF microstructural changes may contribute to ALS-related memory impairment, with word-list learning performance relying more upon the integrity of frontal and temporal connections than memory components associated with story recall.