Hippocampal transcriptome-guided genetic analysis of correlated episodic memory phenotypes in Alzheimer's disease.
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ABSTRACT:
SUBMITTER: Yan J
PROVIDER: S-EPMC4374536 | biostudies-literature | 2015
REPOSITORIES: biostudies-literature
Publications
Hippocampal transcriptome-guided genetic analysis of correlated episodic memory phenotypes in Alzheimer's disease.
Yan Jingwen J Kim Sungeun S Nho Kwangsik K Chen Rui R Risacher Shannon L SL Moore Jason H JH Saykin Andrew J AJ Shen Li L
Frontiers in genetics 20150326
As the most common type of dementia, Alzheimer's disease (AD) is a neurodegenerative disorder initially manifested by impaired memory performances. While the diagnosis information indicates a dichotomous status of a patient, memory scores have the potential to capture the continuous nature of the disease progression and may provide more insights into the underlying mechanism. In this work, we performed a targeted genetic study of memory scores on an AD cohort to identify the associations between ...[more]
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Project description:ObjectiveParkinson's disease (PD) episodic memory impairments are common; however, it is not known whether these impairments are due to hippocampal pathology. Hippocampal Lewy-bodies emerge by Braak stage 4, but are not uniformly distributed. For instance, hippocampal CA1 Lewy-body pathology has been specifically associated with pre-mortem episodic memory performance in demented patients. By contrast, the dentate gyrus (DG) is relatively free of Lewy-body pathology. In this study, we used ultra-high field 7-Tesla to measure hippocampal subfields in vivo and determine if these measures predict episodic memory impairment in PD during life.MethodsWe studied 29 participants with PD (age 65.5 ± 7.8 years; disease duration 4.5 ± 3.0 years) and 8 matched-healthy controls (age 67.9 ± 6.8 years), who completed comprehensive neuropsychological testing and MRI. With 7-Tesla MRI, we used validated segmentation techniques to estimate CA1 stratum pyramidale (CA1-SP) and stratum radiatum lacunosum moleculare (CA1-SRLM) thickness, dentate gyrus/CA3 (DG/CA3) area, and whole hippocampus area. We used linear regression, which included imaging and clinical measures (age, duration, education, gender, and CSF), to determine the best predictors of episodic memory impairment in PD.ResultsIn our cohort, 62.1% of participants with PD had normal cognition, 27.6% had mild cognitive impairment, and 10.3% had dementia. Using 7-Tesla MRI, we found that smaller CA1-SP thickness was significantly associated with poorer immediate memory, delayed memory, and delayed cued memory; by contrast, whole hippocampus area, DG/CA3 area, and CA1-SRLM thickness did not significantly predict memory. Age-adjusted linear regression models revealed that CA1-SP predicted immediate memory (beta[standard error]10.895[4.215], p < .05), delayed memory (12.740[5.014], p < .05), and delayed cued memory (12.801[3.991], p < .05). In the fully-adjusted models, which included all five clinical measures as covariates, only CA1-SP remained a significant predictor of delayed cued memory (13.436[4.651], p < .05).ConclusionsIn PD, we found hippocampal CA1-SP subfield thickness estimated on 7-Tesla MRI scans was the best predictor of episodic memory impairment, even when controlling for confounding clinical measures. Our results imply that ultra-high field imaging could be a sensitive measure to identify changes in hippocampal subfields and thus probe the neuroanatomical underpinnings of episodic memory impairments in patients with PD.
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Project description:There is a large body of research on discourse production in Alzheimer's disease (AD). Some studies have focused on pause production, revealing that patients make extensive use of pauses during speech. This has been attributed to lexical retrieval difficulties, but pausing may also reflect other forms of cognitive impairment as it increases with cognitive load. The aim of the present study was to analyze autobiographical discourse impairment in AD from a broad perspective, looking at pausing behavior (frequency, duration, and location). Our first objective was to characterize discourse changes in mild cognitive impairment (MCI) due to AD. Our second objective was to determine the cognitive and neuroanatomical correlates of these changes. Fifteen patients with MCI due to AD and 15 matched cognitively normal controls underwent an ecological episodic memory task, a full neuropsychological assessment, and a 3D T1-weighted MRI scans. Autobiographical discourse collected from the ecological episodic memory task was recorded, transcribed, and analyzed, focusing on pausing. Intergroup comparisons showed that although patients did not produce more pauses than controls overall, they did make more between-utterance pauses. The number of these specific pauses was positively correlated with patients' episodic memory performance. Furthermore, neuroimaging analysis showed that, in the patient group, their use was negatively correlated with frontopolar area (BA 10) grey matter density. This region may therefore play an important role in the planning of autobiographical discourse production. These findings demonstrate that pauses in early AD may reflect a compensatory mechanism for improving mental time travel and memory retrieval.
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Project description:BackgroundAdults with Down syndrome are at an ultra-high risk of developing early-onset Alzheimer's disease. Episodic memory deficits are one of the earliest signs of the disease, but their association with regional brain atrophy in the population with Down syndrome has not been explored. We aimed to investigate the neuroanatomical correlates of episodic memory in adults with Down syndrome and symptomatic Alzheimer's disease.MethodsSingle-center, cross-sectional study. A total of 139 adults with Down syndrome (85 asymptomatic and 54 with symptomatic Alzheimer's disease) were included in the study (mean age 43.6 ± 10.9 years, 46% female). Episodic memory was assessed using the modified Cued Recall Test. Immediate (trial 1 free immediate recall, trial 3 free immediate recall, total free immediate recall score, and total immediate score) and delayed scores (free delayed recall score and total delayed score) were examined. Cortical thickness from magnetic resonance imaging was determined with surface-based morphometry using the FreeSurfer 6.0 software package. The clusters of reduced cortical thickness were compared between symptomatic and asymptomatic participants to create a cortical atrophy map. Then, the correlation between cortical thickness and the modified Cued Recall Test subscores were separately assessed in symptomatic and asymptomatic subjects, controlling for age, sex, and severity of intellectual disability.ResultsCompared with asymptomatic participants, those with symptomatic Alzheimer's disease showed a pattern of cortical atrophy in posterior parieto-temporo-occipital cortices. In symptomatic subjects, trial 1 immediate free recall significantly correlated with cortical atrophy in lateral prefrontal regions. Trial 3 free immediate recall and total free immediate recall were associated with the most widespread cortical atrophy. Total immediate score was related to posterior cortical atrophy, including lateral parietal and temporal cortex, posterior cingulate cortex, precuneus, and medial temporal lobe areas. Delayed memory scores were associated with cortical atrophy in temporoparietal and medial temporal lobe regions. No significant relationships were observed between episodic memory measures and cortical atrophy in asymptomatic subjects.ConclusionsDifferent episodic memory measures were associated with cortical atrophy in specific brain regions in adults with Down syndrome and Alzheimer's disease. These results overlap with those described in sporadic Alzheimer's disease and further support the similarities between Down syndrome-associated Alzheimer's disease and that in the general population.
| S-EPMC9440567 | biostudies-literature
Project description:Studies of Alzheimer's disease risk-weighted polygenic risk scores (PRSs) for cognitive performance have reported inconsistent associations. This inconsistency is particularly evident when PRSs are assessed independent of APOE genotype. As such, the development and assessment of phenotype-specific weightings to derive PRSs for cognitive decline in preclinical AD is warranted. To this end a episodic memory-weighted PRS (emPRS) was derived and assessed against decline in cognitive performance in 226 healthy cognitively normal older adults with high brain A?-amyloid burden participants from the Australian Imaging, Biomarkers and Lifestyle (AIBL) study. The effect size for decline in a verbal episodic memory was determined individually for 27 genetic variants in a reference sample (n = 151). These were then summed to generate a emPRS either including APOE (emPRSc?APOE) or excluding APOE (emPRSs?APOE ). Resultant emPRS were then evaluated, in a test sample (n = 75), against decline in global cognition, verbal episodic memory and a pre-Alzheimer's cognitive composite (AIBL-PACC) over 7.5 years. The mean (SD) age of the 226 participants was 72.2 (6.6) years and 116 (51.3%) were female. Reference and test samples did not differ significantly demographically. Whilst no association of emPRSs were observed with baseline cognition, the emPRSc? APOE was associated with longitudinal global cognition (-0.237, P = 0.0002), verbal episodic memory (-0.259, P = 0.00003) and the AIBL-PACC (-0.381, P = 0.02). The emPRSs? APOE was also associated with global cognition (-0.169, P = 0.021) and verbal episodic memory (-0.208, P = 0.004). Stratification by APOE ?4 revealed that the association between the emPRS and verbal episodic memory was limited to carriage of no ?4 or one ?4 allele. This was also observed for global cognition. The emPRS and rates of decline in AIBL-PACC were associated in those carrying one ?4 allele. Overall, the described novel emPRS has utility for the prediction of decline in cognition in preclinical AD. This study provides evidence to support the further use and evaluation of phenotype weightings in PRS development.
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