Presentation
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Memory Performance in Alzheimer’s Disease and Primary Progressive Aphasia
Poster C62 in Poster Session C, Wednesday, October 25, 10:15 am - 12:00 pm CEST, Espace Vieux-Port
Jessica Gallegos1, Kyriaki Neophytou1, Craig Stark2, Kyrana Tsapkini1,3; 1Johns Hopkins School of Medicine, 2University of California Irvine, 3Johns Hopkins University
Introduction : The ability to learn and remember new information naturally diminishes in cognitively normal adults across the life span (Cabeza, 2002) but is especially reduced in individuals with Alzheimer’s disease (AD) (Moradi et al., 2017). Recent accounts have also documented verbal episodic memory deficits in primary progressive aphasia (PPA) a neurodegenerative disorder primarily characterized by impaired language performance. This was particularly true for the logopenic variant (lvPPA) (Eikelboom et al., 2018) that has mostly AD pathology. A key process needed to form memories relies on distinguishing similar representations and transforming them into non-overlapping events through pattern separation (McClelland et al., 1995). Prior research has shown that pattern separation abilities are indicative of memory decline both in healthy older individuals as well as in individuals with AD (Stark et al., 2013). However, no prior research has investigated pattern separation abilities in PPA and its variants. The goal of the present study was to investigate the pattern separation abilities in two variants of PPA (lvPPA and non-fluent, nfvPPA) and compare lvPPA to AD, since they share the same pathology. Methods: Pattern separation abilities were evaluated in patients with lvPPA (n=22), nfvPPA (n=10), AD (n=8), and healthy controls (n=7). We used the Mnemonic Similarity Task (MST ) that consisted of (a) an encoding phase of photographs of everyday objects where participants classify objects as “indoor” or “outdoor”, and (b) a surprise recognition phase during which participants are asked to identify the objects presented as “old” (repeated items), “similar” (lure items), or “new” (foil items). As pattern separation index, we measured the Lure Discrimination Index (LDI), i.e., the rate of responding “similar” to a similar lure item minus the rate of responding “similar” to novel objects (foils) (Stark et al., 2013). Analyses included a set of pairwise t-tests investigating LDI differences between: the three patient groups with HC, lvPPA with nfvPPA since they are variants of the same disorder, and lvPPA with AD since they have the same pathology. Results: Group comparisons showed statistically significant differences between HC and AD (p=0.009), as well as between HC and lvPPA (p<0.001), with higher scores for HC. No significant difference was found between HC and nfvPPA. Comparisons of lvPPA with the other two patient groups showed a significantly lower score compared to nfvPPA (p = 0.004), but no significant difference compared to AD. Discussion: Results demonstrated a strong relationship between pattern separation abilities and diagnosis of AD and lvPPA. Importantly, nfvPPA showed a pattern separation profile more similar to HC compared to lvPPA. These results show a strong association between AD and lvPPA, which presumably relates to the shared underlying pathology of these two groups. At the same time, the dissociation between nvPPA and lvPPA may reflect the distinct pattern of atrophies these variants present, with the predominant posterior temporoparietal atrophy observed in lvPPA, a region that is spared in nfvPPA (Eikelboom et al., 2018; Gorno-Tempini et al., 2008).
Topic Areas: Disorders: Acquired,