P7: Subjective memory correlates with hippocampal subfield volumes in normal cognitive aging

Abstract

Objectives: Subjective memory concerns are associated with increased risk for Alzheimer’s disease (AD). Self- perception of frequency of memory slips, in particular, correlates with neuroimaging markers of AD including cerebral amyloid deposition and functional connectivity of the hippocampus and posterior default mode network. The hippocampal complex includes functionally and structurally distinct subfields (cornu ammonis (CA), dentate gyrus, and subiculum) which show selective atrophy in aging and in AD, as well as psychiatric conditions such as major depressive disorder. In the current study, we measured hippocampal subfield volumes in cognitively unimpaired older adults and examined their association with frequency of forgetting and verbal memory.

Methods: Participants were 51 older adults (23M, age 71.0 SD = 6.3) with normal neuropsychological test performance who completed the Memory Functioning Questionnaire (MFQ) and a high-resolution T2-weighted scan of the medial temporal lobe at 3T. The Automatic Segmentation of Hippocampal Subfields (ASHS) processing pipeline was used to extract CA1, CA2, CA3, dentate gyrus, and subiculum volumes. Partial correlations were performed within the total sample to examine the association between subfield volumes and MFQ Frequency of Forgetting (“How often do you….?”) subscale scores, which has been linked to AD neuroimaging markers,19 –21 as well as long delayed recall scores on the California Verbal Learning Test (CVLT-LDR). Covariates were age, sex, and total intracranial volume.

Results: Frequency of Forgetting was significantly correlated with left CA2 [r = .42, P = .003] and right subicular volume [r = .45, P = .001] In contrast, CVLT-LDR was not correlated with any hippocampal subfield volume. No other hippocampal subfield volumes were correlated with Frequency of Forgetting.

Conclusions: The associations between subicular volume, a region implicated in AD, and subjective, but not Objectives memory, suggests that self-perception of frequency of memory lapses in daily life may be sensitive to subtle, early AD-related volumetric changes within the hippocampus. The similar dissociation found for CA2, a region linked to social memory in animal models, is noteworthy. These findings suggest potential neuroanatomical mechanisms for the association between subjective memory concerns and AD risk.