| Abstrakt: |
Background: The ability to form hippocampal‐dependent memories declines steadily in normal aging, and exponentially in people with probable Alzheimer’s disease (AD). Correspondingly, the whole hippocampal formation follows the same trajectories of decline. Critically, pathological changes to distinguishable hippocampal subfields and related cognitive abilities are not well characterized in. Herein, we investigated how these hippocampal subfield and neuropsychological memory measures interact. Method: Structural MRI and neuropsychological data were collected from 29 biomarker‐confirmed individuals on the AD spectrum (ADS) and a comparison group of 17 biomarker‐negative healthy adults to examine the interactions between subfield‐specific hippocampal integrity and cognitive markers. Cognitive assessments included the Wechsler Logical Memory (WMS‐IV) and Hopkins Verbal Learning (HVLT‐R) tests. High resolution hippocampal subfield volumes (CA1, CA2, CA3, dentate gyrus, and subiculum) were measured from a dedicated T2‐weighted MRI slab of the hippocampi (TSE; 0.4 x 0.4 x 2.0 mm), co‐registered to a routine T1‐weighted MRI (MPRAGE; 1.0 x 1.0 x 1.0 mm), using automated hippocampal subfield segmentation (ASHS) software and the UPENN atlas consisting of scans of MCI individuals and older adults (Yushkevich et al., 2015). We performed a cross‐sectional analysis of the relationship between hippocampal subfield volume and behavioral performance on measures of learning and declarative memory. Relationships between hippocampal subfields and neuropsychological subtests were probed using multivariate models contrasting ADS and controls, while controlling for age, education, and intracranial volume. Result: We show that hippocampal subfield volumes robustly predict performance on subtests of WMS‐IV, but not HVLT‐R, regardless of group. Moreover, we report unique contributions of CA3 on learning, subiculum on recognition, and CA2 and CA3 on recall. By dividing the hippocampal formation into distinguishable subfields using ultra high‐resolution MRI, we further elucidate their contributions to ADS‐related neurocognitive declines in learning and memory. Conclusion: Subfield‐specific atrophy in the human hippocampus may constitute a sensitive measure of neurocognitive decline in patients on the AD spectrum. These results suggest that the atrophy of specific hippocampal subfields selectively influence subprocesses of learning and memory, and that these measures may be used to better model disease trajectories among individuals on the Alzheimer’s disease spectrum. [ABSTRACT FROM AUTHOR] |
