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Background: Apathy, defined as a lack of motivation towards goal‐directed behavior, is a common neuropsychiatric symptom in Alzheimer's (AD) and Parkinson's (PD) disease. However, the mechanism underlying apathy is still unclear. Studies have postulated that the degeneration of frontal cortical and subcortical structures may play a major role in the mechanism of apathy. This study investigates whether associations between degeneration in structural and functional connectivity between frontal and subcortical regions contributes to the development of apathetic behavior and whether these associations differ by diseases. Method: Forty‐four patients, 8 with AD, 14 amnestic mild cognitive impairment (aMCI), and 22 PD, received MRI brain scans, a decision‐making behavioral task, cognitive and psychosocial assessments including the dimensional apathy scale (DAS). We quantified functional connectivity and white matter tract integrity for a set of frontal and subcortical regions of interest, and examined the associations among fronto‐subcortical connectivity, behavioral measures, and the DAS. These associations were tested for patient group interactions. Result: Combining AD and aMCI into one patient group, the AD/aMCI group showed worse apathy than PD in terms of the total, the executive, and the behavioral/cognitive subscores (see Table 1), while the DAS emotional subscore was not different between the two groups. For the decision‐making task, the proportion of trial acceptance was similar between the groups, but AD/aMCI had slower decision latency than PD. Group interaction with brain measures was observed in the association between DAS total score and the functional connectivity between the right pars triangularis in the inferior frontal gyrus and the caudate (See Figure 1; interaction effect: beta = ‐.367, p =.0422 FDR corrected). The white matter tract connecting the right pars triangularis to subcortical regions also showed a group interaction with DAS total score but at an uncorrected statistical level (Figure 2; beta = 3.61, p =.0454, uncorrected). Conclusion: Our preliminary analyses exposed phenotypic differences in apathy profiles and decision‐making behavior between AD and PD. Furthermore, the observed functional and structural neurodegenerative changes associated with higher apathy severity may also differ between the two diseases. Future analyses in a larger cohort will examine distinct neurodegeneration patterns between the two diseases. [ABSTRACT FROM AUTHOR]

Background: A healthy dietary pattern, Mediterranean diet (MeDi), has been reported to be associated with better brain and cognition. White matter hyperintensities (WMHs), seen in brain magnetic resonance imaging, are considered to be due to cerebral small vessel diseases and have been shown to predict faster cognitive decline in older adults. However, current evidence on the association between MeDi and WMH is inconsistent and longitudinal data are scarce. This study aims to examine whether better adherence to MeDi is associated with less accumulation of WMH over time. Method: This longitudinal study was conducted among 183 cognitively intact adults aged 20‐80 years. MeDi was calculated from dietary data assessed by a self‐reported food frequency questionnaire, ranging from 0‐55, with a higher score indicating better adherence. WMH was assessed by 3T MRI, and log‐transformed prior to analyses. A one‐sample T‐test was used to examine if WMH burden increased from baseline to follow‐up over an average of five years. Multivariable linear regression was used to estimate the effect of MeDi on the change in WMH. Covariates included age, gender, race/ethnicity, education, IQ, follow‐up interval, caloric intake, baseline WMH, baseline total gray matter volume, and baseline mean cortical thickness. Moderation effects by age (young: <43, middle‐aged: 43‐65, and older: ≥65 years), sex, and race/ethnicity (non‐Hispanic White and other, non‐Hispanic Black, and Hispanic) were examined, followed by stratification analyses. Result: Among all participants, WMH increased from baseline to follow‐up (mean difference [follow‐up‐baseline][standard error(SE)] = 0.31[0.04], p<0.001). A higher MeDi was associated with less increase of WMH (β[SE] = ‐0.014[0.006], p = 0.034), adjusting by all covariates. The association between MeDi and WMH change was moderated by age group (young group as the reference, p‐interaction[middle‐aged*MeDi] = 0.024, p‐interaction[older*MeDi] = 0.017), adjusting by follow‐up interval: the association was observed among the young group (β[SE] = ‐0.038[0.010], p<0.001), but not among the middle‐aged ((β[SE] = ‐0.002[0.013, p = 0.872]) or the older group ((β[SE] = ‐0.002[0.009], p = 0.836). No significant moderation effects by sex or race/ethnicity were found, adjusting by age and follow‐up interval. Conclusion: Better adherence to MeDi was associated with reduced increase of WMH over time. Following a healthy diet, especially at an early age, may help maintain a healthy brain. [ABSTRACT FROM AUTHOR]

Background: The relationship between tau accumulation and cognitive decline in cognitively unimpaired older adults is still unclear. The tau PET tracer 18F‐MK‐6240 has shown favorable imaging carachteristics to identify early tau accumulation in older adults. Method: We evaluated the relationship between in vivo tau levels (18F‐MK‐6240) and retrospective cognitive change over 5 years in episodic memory, processing speed, and reasoning. For tau quantification, we created a set of regions of Interest (ROIs), selected a priori based on previous literature: 1) Total‐ROIs comprising all 16 areas selected; 2) Medial Temporal Lobe‐ROI, 3) Lateral Temporal Lobe‐ROI and Cingulate/Parietal lobel‐ROI. Result: 41 cognitively unimpaired older adults was included in the study, 82% classified as amyloid‐b negative. Higher tau burden in most meta‐ROIs was associated with steeper decline in memory and speed. There were no associations between tau and reasoning change. Conclusion: Our finding reforces the notion that early tau accumulation in areas related tio Alzheimer's disease is associated with cognitive decline in cognitively unimpaired individuals, even in a sample characterized with low amyloid‐b pathology. The novel contributin of this work is the relevante of tau accumulation beyond memory, particularly in processing speed decline. [ABSTRACT FROM AUTHOR]

Background: Aging research has repeatedly shown that crystallized abilities, cognitive processes reliant on learned knowledge, are well preserved well into old age. On the other hand, fluid abilities, processes that are not knowledge‐dependent, show decline as early as the third decade of life. It is still unclear what mechanism enables the two starkly contrasting aging trajectories to exist all within the same brains. Method: From the Reference Ability Neural Network (RANN) study, 181 participants (age=51.2±17.2, 101females) with both baseline and 5‐year follow‐up diffusion weighted imaging data were included in the current analysis. Based on fMRI activation data, the set of brain regions were derived that are associated with performance of each of four cognitive abilities: vocabulary, processing speed, episodic memory, and reasoning. Using these regions as seeds, white matter tracts connecting the brain regions for each ability were extracted and used to calculate the mean fiber density associated with each ability. Three models, linear, partial linear, and quadratic were performed to model the longitudinal changes in fiber density for each ability. Mixed effect regression was used to test whether vocabulary, the only crystallized ability, shows more gradual decline than white matter for the other three abilities, which were all fluid abilities. The non‐linear trend of age was modeled using B‐splines with the knot point selection based on Bayesian information criteria (BIC). Result: Consistent with cross‐sectional results reported in Gazes et al. 2020, mean fiber density for white matter tracts associated with the vocabulary ability was shown to follow a slower decline with age than that for the three fluid abilities – processing speed [F(2,1251)=57.5, p<.001], episodic memory [F(2,1251)=5.32, p<.001), and reasoning [F(2,1251)=4.05, p<.001]. Figure 1 shows the age‐related trajectory modeled with quadratic trend, which was the best fitting model based on BIC values. Vocabulary, in purple, clearly demonstrates a shallower decline than the other three abilities for fiber density. Conclusion: This study demonstrated that longitudinal changes in the microstructural integrity of white matter tracts are better preserved for vocabulary, a crystallized ability, than that for the three fluid abilities, suggesting that preservation of white matter contributes to the maintenance of crystallized abilities with age. [ABSTRACT FROM AUTHOR]

Background: Reduced awareness of one’s financial decision‐making abilities (financial awareness) can result in costly financial mistakes (e.g., forgetting to pay credit card dues) and increase one’s vulnerability to financial exploitation (e.g., getting scammed). In cognitively healthy older adults, thinner right medial temporal cortex is associated with overconfidence in one’s financial decision‐making abilities. However, it is important to examine other neuroimaging metrics to create a comprehensive picture of the links between brain and financial awareness in healthy older adults. In the current study, we examined the white matter correlates of financial awareness and hypothesized that the tracts connecting the right temporal‐frontal regions would be most strongly correlated with financial awareness. Method: Design ‐ Cross‐sectional, prospective study. Setting ‐ Community‐based. Participants: 44 individuals were included with mean age=68.43 years (SD=5.1), mean education=15.88 (SD=2.41), 60% = women, 67% = White, 30% = Black and 3% = other races, and 95% = non‐Hispanics. Measures: Awareness Metrics – Financial awareness was measured by integrating metacognitive ratings into the Objective Financial Competency Assessment Inventory. Before each item, we obtained confidence ratings regarding performance on that item. Level of awareness was operationalized via a calibration score reflecting the difference between average performance and average confidence, reflecting the extent to which individuals were over‐ or under‐confident. Mean Diffusivity – Data were processed with Tracts Constrained by Underlying Anatomy toolbox distributed as part of the FreeSurfer library (v5.3) which produced averages of mean diffusivity for 18 white matter tracts. Lower mean diffusivity values indicated higher white matter integrity. Result: The right superior longitudinal fasciculus–temporal (r = 0.437, p = 0.003) and parietal (r = 0.433, p = 0.003) bundles had the strongest correlations with calibration scores such that higher (i.e., worse) diffusivity was associated with values reflecting over‐confidence. Conclusion: Our findings converge with the growing literature on the unique role of the right hemisphere temporal connections in supporting financial awareness. We find an equally important role for right parietal‐frontal connections in financial awareness. Our findings are in line with studies on financial exploitation in which the right parietal and temporal pathways were found to be involved in scam susceptibility. [ABSTRACT FROM AUTHOR]

Background: Tau PET imaging, while highly predictive of the onset of dementia, requires injection of radioactive compound and costs much more than MRI scans. The goal of this study was to test whether multi‐shell diffusion MRI can generate diffusion measures that predict tau burden. While DTI measures such as fractional anisotropy (FA) and mean diffusivity have been examined in aging and dementia studies, the DTI model is now recognized as being too simplistic and has been shown to mistakenly calculated higher FA than controls in atrophied white matter. Multi‐shell diffusion MRI allows more accurate modeling of crossing fibers and has been demonstrated to detect atrophy in Alzheimer's disease. Method: In the current study, a sample of 14 healthy older adults was scanned with multi‐shell diffusion MRI and tau PET imaging using [18F]MK‐6240 tracer. For 10 of the participants, diffusion was obtained on average 222 days before tau PET while the 4 other participants were scanned with diffusion MRI 211 days after tau PET. Standardized uptake value ratio (SUVR) for the left and the right entorhinal cortex were quantified relative to the cerebellar mean uptake. Diffusion data were processed through MRtrix's fiber‐based analysis pipeline to obtain the whole brain fiber density and cross‐section (FDC) measure. Using tracts connected to the parahippocampal gyrus as masks, we tested whether FDC of the fibers in the white matter tracts connected to the parahippocampal gyrus correlated negatively with the tau SUVR in the entorhinal cortex within each hemisphere, correcting for age. Result: After correction for multiple comparisons using family‐wise error approach, FDC for fibers connected to the left parahippocampal gyrus were negatively correlated with the left entorhinal tau SUVR as shown in figure attached. The mean FDC over the significant fibers and EC tau SUVR showed that r = ‐.707, p=0.007. Conclusion: The negative correlation supports our hypothesis that greater tau burden is associated with lower fiber density and cross‐section in white matter tracts directly connected to the parahippocampal cortex. This encouraging result demonstrates the potential for multi‐shell diffusion as an alternative to PET for early detection of tau burden in cognitively healthy older adults. [ABSTRACT FROM AUTHOR]