Age-related volumetric alterations in hippocampal subiculum region are associated with reduced retention of the “when” memory component

Abstract

Although age-related differences in episodic memory function are well established, the differential reduction in fine-grain memory components and its underlying hippocampal mechanism remains unclear. Hence, the current study investigated, first, age-related differences in the recollection of the four components (who, when, where, and what) of verbal episodic memory and, second, these components’ associations with volumetric alterations in the hippocampal subfields. A total of 60 older and younger adults completed the Logical Memory test. The measurements of the volumes of the hippocampal subfields were obtained. The results revealed that older age was associated with poorer learning performance for when, where, and what components but not for who component; the reduced learning scores were differentially correlated with the age-related regional vulnerability of the dentate gyrus, CA1 subfield, and subiculum. The age-related vulnerability in the retention of the when component was associated with smaller subiculum, CA1, CA4, and dentate gyrus, but a reduction in the subiculum alone mediated the inverse relationship between age and the retention score for the when component. Our findings underscore the value of differentiating between memory components in evaluations of verbal contextual episodic memory which allows the analyst to examine aging-related associations between subtle cognitive changes and hippocampal substructures.