A Multi-Cohort Study of ApoE ɛ4 and Amyloid-ß Effects on the Hippocampus in Alzheimer's Disease.

The apolipoprotein E (APOE) gene has been consistently shown to modulate the risk of Alzheimer's disease (AD). Here, using an AD and normal aging dataset primarily consisting of three AD multi-center studies (n = 1,781), we compared the effect of APOE and amyloid-ß (Aß) on baseline hippocampal volumes in AD patients, mild cognitive impairment (MCI) subjects, and healthy controls. A large sample of healthy adolescents (n = 1,387) was also used to compared hippocampal volumes between APOE groups. Subjects had undergone a magnetic resonance imaging (MRI) scan and APOE genotyping. Hippocampal volumes were processed using FreeSurfer. In the AD and normal aging dataset, hippocampal comparisons were performed in each APOE group and in ɛ4 carriers with positron emission tomography Aß who were dichotomized (Aß+/Aß-) using previous cut-offs. We found a linear reduction in hippocampal volumes with ɛ4 carriers possessing the smallest volumes, ɛ3 carriers possessing intermediate volumes, and ɛ2 carriers possessing the largest volumes. Moreover, AD and MCI ɛ4 carriers possessed the smallest hippocampal volumes and control ɛ2 carriers possessed the largest hippocampal volumes. Subjects with both APOE ɛ4 and Aß+ had the lowest hippocampal volumes when compared to Aß- ɛ4 carriers, suggesting a synergistic relationship between APOE ɛ4 and Aß. However, we found no hippocampal volume differences between APOE groups in healthy 14-year-old adolescents. Our findings suggest that the strongest neuroanatomic effect of APOE ɛ4 on the hippocampus is observed in AD and groups most at risk of developing the disease, whereas hippocampi of old and young healthy individuals remain unaffected.

Tract Based Spatial Statistic Reveals No Differences in White Matter Microstructural Organization between Carriers and Non-Carriers of the APOE ɛ4 and ɛ2 Alleles in Young Healthy Adolescents.

The apolipoprotein E (APOE) ɛ4 allele is the best established genetic risk factor for Alzheimer's disease (AD) and has been previously associated with alterations in structural gray matter and changes in functional brain activity in healthy middle-aged individuals and older non-demented subjects. In order to determine the neural mechanism by which APOE polymorphisms affect white matter (WM) structure, we investigated the diffusion characteristics of WM tracts in carriers and non-carriers of the APOE ɛ4 and ɛ2 alleles using an unbiased whole brain analysis technique (Tract Based Spatial Statistics) in a healthy young adolescent (14 years) cohort. A large sample of healthy young adolescents (n = 575) were selected from the European neuroimaging-genetics IMAGEN study with available APOE status and accompanying diffusion imaging data. MR Diffusion data was acquired on 3T systems using 32 diffusion-weighted (DW) directions and 4 non-DW volumes (b-value = 1,300 s/mm² and isotropic resolution of 2.4×2.4×2.4  mm). No significant differences in WM structure were found in diffusion indices between carriers and non-carriers of the APOE ɛ4 and ɛ2 alleles, and dose-dependent effects of these variants were not established, suggesting that differences in WM structure are not modulated by the APOE polymorphism. In conclusion, our results suggest that microstructural properties of WM structure are not associated with the APOE ɛ4 and ɛ2 alleles in young adolescence, suggesting that the neural effects of these variants are not evident in 14-year-olds and may only develop later in life.

No differences in hippocampal volume between carriers and non-carriers of the ApoE ε4 and ε2 alleles in young healthy adolescents.

Alleles of the apolipoprotein E (ApoE) gene are known to modulate the genetic risk for developing late-onset Alzheimer's disease (AD) and have been associated with hippocampal volume differences in AD. However, the effect of these alleles on hippocampal volume in younger subjects has yet to be clearly established. Using a large cohort of more than 1,400 adolescents, this study found no hippocampal volume or hippocampal asymmetry differences between carriers and non-carriers of the ApoE ε4 or ε2 alleles, nor dose-dependent effects of either allele, suggesting that regionally specific effects of these polymorphisms may only become apparent in later life.

Do you see what I see? Sex differences in the discrimination of facial emotions during adolescence.

During adolescence social relationships become increasingly important. Establishing and maintaining these relationships requires understanding of emotional stimuli, such as facial emotions. A failure to adequately interpret emotional facial expressions has previously been associated with various mental disorders that emerge during adolescence. The current study examined sex differences in emotional face processing during adolescence. Participants were adolescents (n = 1951) with a target age of 14, who completed a forced-choice emotion discrimination task. The stimuli used comprised morphed faces that contained a blend of two emotions in varying intensities (11 stimuli per set of emotions). Adolescent girls showed faster and more sensitive perception of facial emotions than boys. However, both adolescent boys and girls were most sensitive to variations in emotion intensity in faces combining happiness and sadness, and least sensitive to changes in faces comprising fear and anger. Furthermore, both sexes overidentified happiness and anger. However, the overidentification of happiness was stronger in boys. These findings were not influenced by individual differences in the level of pubertal maturation. These results indicate that male and female adolescents differ in their ability to identify emotions in morphed faces containing emotional blends. The findings provide information for clinical studies examining whether sex differences in emotional processing are related to sex differences in the prevalence of psychiatric disorders within this age group.

Donepezil in Parkinson's disease dementia: a randomized, double-blind efficacy and safety study.

Parkinson's disease dementia (PDD) is associated with cholinergic deficits. This report presents an efficacy and safety study of the acetylcholinesterase inhibitor donepezil hydrochloride in PDD. PDD patients (n = 550) were randomized to donepezil (5 or 10 mg) or placebo for 24 weeks. Coprimary end points were the Alzheimer's Disease Assessment Scale-cognitive subscale (ADAS-cog) and Clinician's Interview-Based Impression of Change plus caregiver input (CIBIC+; global function). Secondary end points measured executive function, attention, activities of daily living (ADLs), and behavioral symptoms. Safety and tolerability were assessed. ADAS-cog mean changes from baseline to week 24 (end point) were not significant for donepezil in the intent-to-treat population by the predefined statistical model (difference from placebo: -1.45, P = .050, for 5 mg; -1.45, P = .076, for 10 mg). Alternative ADAS-cog analysis, removing the treatment-by-country interaction term from the model, revealed significant, dose-dependent benefit with donepezil (difference from placebo: -2.08, P = .002, for 5 mg; -3.31, P < .001, for 10 mg). The 10-mg group, but not the 5-mg group, had significantly better CIBIC+ scores compared with placebo (3.7 vs 3.9, P = .113, for 5 mg; 3.6 vs 3.9, P = .040, for 10 mg). Secondary end points-Mini-Mental State Exam; Delis-Kaplan Executive Function System; Brief Test of Attention, representing cognitive functions particularly relevant to PDD-showed significant benefit for both donepezil doses (P ≤ .007). There were no significant differences in ADLs or behavior. Adverse events were more common with donepezil but mostly mild/moderate in severity. Although the study did not achieve its predefined primary end points, it presents evidence suggesting that donepezil can improve cognition, executive function, and global status in PDD. Tolerability was consistent with the known safety profile of donepezil. © 2012 Movement Disorder Society.