Semantic clustering and hippocampal atrophy in mild cognitive impairment and Alzheimer's disease

Abstract

Methods: Eight subjects with mild cognitive impairment (MCI) and 14 with Alzheimer’s disease (AD) completed the California Verbal Learning Test (CVLT) and T1-weighted 3D MPRAGE scans. Semantic clustering, the ratio of words from the same category recalled in clusters, was calculated for the learning, short delay and long delay trials to study the effect of strategy use. Results: We found trend-level association between semantic clustering at learning and the left hippocampus (pcorrected=0.08) but no significant associations with initial learning without clustering. Short-delayed free recall and semantic clustering at the short-delayed free recall demonstrated a positive association with hippocampal radial distance on the left (pcorrected=0.025 and pcorrected=0.037, resp.). In addition to significant left-sided associations, long-delayed free recall and semantic clustering at the long-delayed free recall showed trend-level associations on the right (left pcorrected=0.024 and pcorrected=0.039, resp; right pcorrected=0.066 and pcorrected=0.08). Regionally the effects were most pronounced in the CA1 hippocampal subregion.