Size does matter in the long run - Hippocampal and cortical volume predict recall across weeks

Objective: To study the morphometric determinants of recall of verbal material for an extended period in an adult lifespan sample. Methods: Healthy adults of varying ages were studied using automated segmentation of MRI scans with volumes of hippocampus, cortex, and white matter, and verbal memory tests assessing recall after 5 minutes, 30 minutes, and a mean period of 11 weeks. Stepwise regression analyses were performed with 5 minutes, 30 minutes, and 11-week recall as the dependent variables. Hippocampal, cortical, and white matter volumes were included in the initial set of predictor variables in each case, and the analyses were repeated with age as an additional predictor variable. Results: When age was not included, cortical volume was the only variable predicting recall after 5 and 30 minutes, whereas hippocampal and cortical volumes predicted recall after 11 weeks. When age was included in the model, this was the only variable predicting recall after 5 and 30 minutes, whereas age and hippocampus gave contributions in prediction of recall after several weeks. Conclusion: This study supports a critical role of cortical and hippocampal size in recall. Hippocampal size seems more important in recall after 11 weeks than after a shorter time interval.