Chris Bradley

BackgroundStory recall tests have shown variable sensitivity to rate of cognitive decline in individuals with Alzheimer’s disease biomarkers. Although SR tasks are typically scored by obtaining a sum of items recalled, item-level analyses may provide additional sensitivity to change and AD processes. Here, we examined the difficulty and discrimination indices of each item from the Logical Memory SR task, and determined if these metrics differed by recall conditions, story version, lexical categories, serial position, and amyloid status.Methodsn = 1,141 participants from the Wisconsin Registry for Alzheimer’s Prevention longitudinal study who had item-level data were included in these analyses, as well as a subset of n = 338 who also had amyloid positron emission tomography imaging. LM data were categorized into four lexical categories, and by serial position. We calculated difficulty and discriminability/memorability by item, category, and serial position and ran separate repeated measures ANOVAs for each recall condition, lexical category, and serial position. For the subset with amyloid imaging, we used a two-sample t-test to examine whether amyloid positive and amyloid negative groups differed in difficulty or discrimination for the same summary metrics.ResultsIn the larger sample, items were more difficult in the delayed recall condition across both story A and story B. Item discrimination was higher at delayed than immediate recall, and proper names had better discrimination than any of the other lexical categories or serial position groups. In the subsample with amyloid PET imaging, proper names were more difficult for Aβ+ than Aβ−; items in the verb and “other” lexical categories and all serial positions from delayed recall were more discriminate for the Aβ+ group compared to the Aβ− group.ConclusionThis study provides empirical evidence that both LM stories are effective at discriminating ability levels and amyloid status, and that individual items vary in difficulty and discrimination by amyloid status, while total scores do not. These results can be informative for the future development of sensitive tasks or composite scores for early detection of cognitive decline.