Category: Parkinson's Disease: Neuroimaging
Objective: As part of the Ontario Neurodegenerative Disease Research Initiative, we investigated group differences in functional connectivity within two distinct memory networks: posterior medial network (PMN) and the anterior temporal network (ATN), in APOE genotyped (ε3ε3, ε3ε4, ε4ε4) Parkinson’s disease (PD; N=116) & Alzheimer’s disease (AD; N=107) patients.
Background: Episodic memory problems are often a first subjective complaint in PD, despite this being synonymous with AD. Moreover, episodic memory deficits are frequently seen in carriers with the ε4 variant of the APOE gene. Thus, these complaints in both syndromes may be due to similar memory network disturbances caused by the presence of the APOE ε4 allele.
Method: Linear models assessed the effects of diagnosis and APOE on network connectivity and the Face-Name Associative Memory Exam. Two measures of episodic recognition were used: item and associative memory, both of which are especially sensitive to early AD. We used partial correlations to explore the associations between network connectivity and memory performance. Age, sex and educational attainment were covaried.
Results: There was a main effect of diagnosis on connectivity within the PMN (F(1,218)=7.830, p=0.006, np2=.035), but no effect on connectivity within the ATN (p=0.366). We also found a main effect of APOE on ATN connectivity (F(1,218)=3.998, p=0.020, np2=.037) but no effects of APOE on PMN connectivity. A similar pattern of effects of APOE and diagnosis was found on the Memory Exam. Specifically, there was an effect of diagnosis on associative recognition (F(1,213)=6.827, p=.010, np2=.032), but not on item recognition (p=.454). By contrast, APOE had an effect on item recognition (F(1,213)=4.142, p=.017, np2=.039) but not on associative recognition scores. PMN connectivity was correlated with associative recognition (r=0.228, p=001). No significant correlates were found for item recognition.
Conclusion: Our findings show a similar profile of item memory recognition performance in AD and PD. The APOE genotype predicted this shared phenotype. A more challenging test of associative memory revealed greater impairments in the AD compared to the PD group and were underpinned by reduced PMN connectivity. In summary, the ATN network may be important to the mechanistic understanding of how genetics impact overlapping clinical phenotypes.
To cite this abstract in AMA style:
G. Coughlan, P. Mclaughlin, K. Sunderland, M. Borrie, C. Fischer, A. Frank, M. Freedman, S. Kumar, S. Pasternak, B. Pollock, T. Rajji, D. Seitz, D. Tang-Wai, C. Tartaglia, J. Dewar, D. Kwan, B. Tan, D. Grimes, M. Jog, T. Lang, C. Marras, T. Steeves, D. Bulman, A. Dilliott, M. Ghani, R. Hegele, J. Robinson, E. Rogaeva, S. Farhan, R. Bartha, N. Nanayakkara, J. Ramirez, C. Scott, S. Symons, C. Berezuk, M. Holmes, S. Adamo, M. Ozzoude, A. Theyers, S. Arnott, D. Beaton, W. Lou, S. Sujanthan, B. Levine, J. Orange, A. Peltsch, A. Roberts, A. Troyer, M. Binns, S. Black, S. Strother, M. Moscovitch, C. Grady, M. Masellis. Distinct memory networks in Parkinson’s disease (PD) and Alzheimer’s disease (AD): Effects of APOE [abstract]. Mov Disord. 2021; 36 (suppl 1). https://www.mdsabstracts.org/abstract/distinct-memory-networks-in-parkinsons-disease-pd-and-alzheimers-disease-ad-effects-of-apoe/. Accessed June 15, 2025.« Back to MDS Virtual Congress 2021
MDS Abstracts - https://www.mdsabstracts.org/abstract/distinct-memory-networks-in-parkinsons-disease-pd-and-alzheimers-disease-ad-effects-of-apoe/