%0 Journal Article %J J Alzheimers Dis %D 2020 %T APOE4 Status is Related to Differences in Memory-Related Brain Function in Asymptomatic Older Adults with Family History of Alzheimer's Disease: Baseline Analysis of the PREVENT-AD Task Functional MRI Dataset. %A Rabipour, Sheida %A Rajagopal, Sricharana %A Yu, Elsa %A Pasvanis, Stamatoula %A Lafaille-Magnan, Marie-Elyse %A Breitner, John %A Rajah, M Natasha %X

BACKGROUND: Episodic memory decline is one of the earliest symptoms of late-onset Alzheimer's disease (AD). Older adults with the apolipoprotein E ɛ4 (+APOE4) genetic risk factor for AD may exhibit altered patterns of memory-related brain activity years prior to initial symptom onset.

OBJECTIVE: Here we report the baseline episodic memory task functional MRI results from the PRe-symptomatic EValuation of Experimental or Novel Treatments for Alzheimer's Disease cohort in Montreal, Canada, in which 327 healthy older adults were scanned within 15 years of their parent's conversion to AD.

METHODS: Volunteers were scanned as they encoded and retrieved object-location spatial source associations. The task was designed to discriminate between brain activity related to spatial source recollection and object-only (recognition) memory. We used multivariate partial least squares (PLS) to test the hypothesis that +APOE4 adults with family history of AD would exhibit altered patterns of brain activity in the recollection-related memory network, comprised of medial frontal, parietal, and medial temporal cortices, compared to APOE4 non-carriers (-APOE4). We also examined group differences in the correlation between event-related brain activity and memory performance.

RESULTS: We found group similarities in memory performance and in task-related brain activity in the recollection network, but differences in brain activity-behavior correlations in ventral occipito-temporal, medial temporal, and medial prefrontal cortices during episodic encoding.

CONCLUSION: These findings are consistent with previous literature on the influence of APOE4 on brain activity and provide new perspective on potential gene-based differences in brain-behavior relationships in people with first-degree family history of AD.

%B J Alzheimers Dis %V 76 %P 97-119 %8 2020 %G eng %N 1 %1 https://www.ncbi.nlm.nih.gov/pubmed/32474466?dopt=Abstract %R 10.3233/JAD-191292 %0 Journal Article %J J Alzheimers Dis %D 2018 %T Bi-directional Association of Cerebrospinal Fluid Immune Markers with Stage of Alzheimer's Disease Pathogenesis. %A Meyer, Pierre-François %A Savard, Mélissa %A Poirier, Judes %A Labonte, Anne %A Rosa-Neto, Pedro %A Weitz, Tara M %A Town, Terrence %A Breitner, John %X

Immune mechanisms may be important in the pathogenesis of Alzheimer's disease (AD). Yet, studies comparing cerebrospinal fluid (CSF) and plasma immune marker levels of healthy and demented individuals have yielded conflicting results. We analyzed CSF from 101 members of the parental history-positive PREVENT-AD cohort of healthy aging adults, and 237 participants without dementia from the initial cohort of the Alzheimer's Disease Neuroimaging Initiative (ADNI-1). Following recent practice, we used the biomarkers total-tau and amyloid-β1-42 to allocate participants from each study into four stages of AD pathogenesis: Stage 0 (no abnormality), Stage 1 (reduced amyloid-β1-42), Stage 2 (reduced amyloid-β1-42 and increased total-tau), or "Suspected Non-Alzheimer Pathology" (elevated total-tau only). Investigating the PREVENT-AD participants' CSF assay results for 19 immune/inflammatory markers, we found six that showed a distinct bi-directional relationship with pathogenetic stage. Relative to Stage 0, these were diminished at Stage 1 but strongly increased at Stage 2. Among the ADNI participants (90 healthy controls and 147 with mild cognitive impairment), we found that 23 of 83 available CSF markers also showed this distinct pattern. These results support recent observations that immune activation may become apparent only after the onset of both amyloid and tau pathologies. Unexpectedly, they also suggest that immune marker activity may diminish along with earliest appearance of amyloid-β plaque pathology. These findings may explain discordant results from past studies, and suggest the importance of characterizing the extent of AD pathology when comparing clinical groups.

%B J Alzheimers Dis %V 63 %P 577-590 %8 2018 %G eng %N 2 %1 http://www.ncbi.nlm.nih.gov/pubmed/29660934?dopt=Abstract %R 10.3233/JAD-170887 %0 Journal Article %J J Alzheimers Dis %D 2018 %T Healthy versus Entorhinal Cortical Atrophy Identification in Asymptomatic APOE4 Carriers at Risk for Alzheimer's Disease. %A Konishi, Kyoko %A Joober, Ridha %A Poirier, Judes %A MacDonald, Kathleen %A Chakravarty, Mallar %A Patel, Raihaan %A Breitner, John %A Bohbot, Véronique D %K Aged %K Alleles %K Alzheimer Disease %K Apolipoprotein E4 %K Atrophy %K Case-Control Studies %K Entorhinal Cortex %K Female %K Heterozygote %K Hippocampus %K Humans %K Magnetic Resonance Imaging %K Male %K Middle Aged %K Risk Factors %K Spatial Memory %X

Early detection of Alzheimer's disease (AD) has been challenging as current biomarkers are invasive and costly. Strong predictors of future AD diagnosis include lower volume of the hippocampus and entorhinal cortex, as well as the ɛ4 allele of the Apolipoprotein E gene (APOE) gene. Therefore, studying functions that are critically mediated by the hippocampus and entorhinal cortex, such as spatial memory, in APOE ɛ4 allele carriers, may be key to the identification of individuals at risk of AD, prior to the manifestation of cognitive impairments. Using a virtual navigation task developed in-house, specifically designed to assess spatial versus non-spatial strategies, the current study is the first to differentiate functional and structural differences within APOE ɛ4 allele carriers. APOE ɛ4 allele carriers that predominantly use non-spatial strategies have decreased fMRI activity in the hippocampus and increased atrophy in the hippocampus, entorhinal cortex, and fimbria compared to APOE ɛ4 allele carriers who use spatial strategies. In contrast, APOE ɛ4 allele carriers who use spatial strategies have grey matter levels comparable to non-APOE ɛ4 allele carriers. Furthermore, in a leave-one-out analysis, grey matter in the entorhinal cortex could predict navigational strategy with 92% accuracy.

%B J Alzheimers Dis %V 61 %P 1493-1507 %8 2018 %G eng %N 4 %1 http://www.ncbi.nlm.nih.gov/pubmed/29278888?dopt=Abstract %R 10.3233/JAD-170540