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“Et tu, Whatsyourname?” Evidence that hippocampal atrophy underlies age-related difficulties at recalling people’s names
Poster Session D, Saturday, September 13, 5:00 - 6:30 pm, Field House
Jana Reifegerste1, Lauren E. Russell2, João Veríssimo3, Daniel W. Lipscomb4, Michael T. Ullman1; 1Georgetown University, 2The Johns Hopkins University School of Medicine, 3University of Lisbon, 4University of Virginia
We have increasing difficulty recalling people’s names as we get older. However, both the pattern of the declines and the reasons why they occur have remained unclear. Given the striking hippocampal atrophy in aging, and evidence implicating the hippocampus in recalling as well as learning associations, we hypothesized that hippocampal atrophy may contribute to age-related declines at recalling proper names. Names learned later in life should be particularly susceptible to the hippocampal declines, given that knowledge learned in the hippocampus gradually undergoes ‘systems consolidation’ (the formation of direct connections between neocortical representations that were initially indirectly linked via the hippocampus), leading to a decreasing reliance on this structure with time. Specifically, names learned later in life — that is, with later ages-of-acquisition — should thus show particular recall declines because less time has passed since they were learned as compared to earlier-learned names, so they should depend more on the hippocampus. In a cross-sectional continuous-age design, we asked 126 native U.S. English speakers (ages 18-85) to name pictures of 90 famous people — specifically, 10 people who were especially famous in each of the nine decades from the 1930s to the 2010s (e.g., Amelia Earhart in the 1930s, Malcom X in the 1960s, Mike Pence in the 2010s). We predicted particular age-related declines in retrieving the names of people who were famous more recently (e.g., from the 2010s), since those names should generally have been acquired more recently, and thus should have later ages-of-acquisition. Age-of-acquisition estimates given by each subject for each name confirmed that names from later decades indeed had later ages-of-acquisition. We also segmented hippocampal and other gray matter volumes from whole brain and high-resolution hippocampal MRI scans. Unlike in previous studies, overall proper name recall did not decline with age. Instead, there was actually a positive effect of age on naming performance (accuracy increases, reaction-time decreases) for names from early decades (e.g., 1930s-1950s). However, this age effect became increasingly negative (accuracy decreases, reaction-time increases) for names from later decades (1990s-2010s). The results were robust, also holding when controlling for name frequency and for which names were known to individual participants. Preliminary mediation analyses suggest that the age-related performance declines found for later decades were mediated by atrophy of the hippocampus, but not by any of several control structures (entorhinal cortex, inferior frontal gyrus, middle temporal gyrus). In sum, the evidence suggests that as we get older, we do not seem to have more difficulty retrieving people’s names that were learned earlier in life. Rather, age-related naming difficulties may be limited to names learned during (later) adulthood. Further, these naming declines appear to be driven by atrophy of the hippocampus. We discuss basic research and translational implications, including the possibility that therapeutic approaches that improve hippocampal function may alleviate naming difficulties in aging – and perhaps also in Alzheimer’s disease, in which such difficulties are even more pronounced, and in which the hippocampus declines to an even greater extent.
Topic Areas: Language Development/Acquisition, Language Production