Individual differences in anterograde memory for details relate to posterior hippocampal volume

In recent years, there has been a growing interest in individual differences in autobiographical memory. The ability to recall details from personal past events correlates with the volume of specific hippocampal subfields in healthy adults. Although the posterior hippocampus is believed to process detailed memory representations independently of the memory's age, little is known about individual differences in the ability to recall newly encoded events in detail, and how these differences relate to hippocampal subregions. In this preregistered study, we scored the story recalls from 89 healthy middle-aged participants with a newly designed method that allows to distinguish information recalled in detail from gist recall (i.e., when only the general idea is recalled). After a 20-min delay, detailed information was transformed into gists, which is in line with recent evidence that gists can emerge rapidly after a new experience. In addition, we segmented the anterior and posterior hippocampal subfields CA1, CA2/3, dentate gyrus, and subiculum from high-resolution structural MRI. As predicted, the volume of the posterior hippocampus was positively correlated with the detail score but not with the gist score, yet this effect was significant in the right hemisphere only. We also observed trends towards associations between the detail score and specific subfields of the right posterior hippocampus, but none survived statistical correction for multiple comparisons. Finally, we found no evidence for the expected age-related increase in the use of gists over details. Taken together, these results suggest that the posterior hippocampus supports detail memory in the recall of both remote and newly acquired memories.