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Limbic-predominant age-related TDP-43 encephalopathy (LATE) affects approximately one-third of older individuals and is associated with cognitive impairment. However, there is a highly incomplete understanding of the genetic determinants of LATE neuropathologic changes (LATE-NC) in diverse populations. The defining neuropathologic feature of LATE-NC is TDP-43 proteinopathy, often with comorbid hippocampal sclerosis (HS). In terms of genetic risk factors, LATE-NC and/or HS are associated with single nucleotide variants (SNVs) in 3 genes-TMEM106B (rs1990622), GRN (rs5848), and ABCC9 (rs1914361 and rs701478). We evaluated these 3 genes in convenience samples of individuals of African ancestry. The allele frequencies of the LATE-associated alleles were significantly different between persons of primarily African (versus European) ancestry: In persons of African ancestry, the risk-associated alleles for TMEM106B and ABCC9 were less frequent, whereas the risk allele in GRN was more frequent. We performed an exploratory analysis of data from African-American subjects processed by the Alzheimer's Disease Genomics Consortium, with a subset of African-American participants (n = 166) having corroborating neuropathologic data through the National Alzheimer's Coordinating Center (NACC). In this limited-size sample, the ABCC9/rs1914361 SNV was associated with HS pathology. More work is required concerning the genetic factors influencing non-Alzheimer disease pathology such as LATE-NC in diverse cohorts.

Background: Subjective cognitive decline (SCD) is a preclinical stage of Alzheimer's disease (AD), with correlations to cerebral amyloid and tau and accelerated cognitive decline. Studies have also revealed an association between sleep fragmentation and such AD biomarkers and cognitive decline, suggesting that cognitive function should be monitored in individuals experiencing excessive sleepiness. It is unclear if and how sleep dysfunction relates to SCD apart from AD biomarkers, as well as symptoms related to SCD and sleep dysfunction, such as depression. Furthermore, studies of SCD and sleep dysfunction have primarily focused on non‐Hispanic Whites. Hence, a better understanding of how sleep impacts preclinical AD risk in SCD is needed in more diverse cohorts. We investigated the cross‐sectional relationship between excessive sleepiness in cognitively normal older adults and SCD symptoms linked to cognitive domains in a cohort consisting of NHWs and Black/African Americans (B/AA). Method: This retrospective cross‐sectional study included cognitively normal older participants (n = 147, age> 60 years, 61 B/AA, 86 NHW) evaluated at the NYU Alzheimer's Disease Research Center. Participants underwent Uniform Data Set 3.0 psychometric testing to confirm normal cognition, Epworth Sleepiness Scale (ESS), Geriatric Depression Scale (GDS), and the Cognitive Change Index (CCI) as a measure of SCD. The CCI was further divided into subscores of non‐amnestic (i.e. executive) and amnestic domains (i.e. memory). Participants underwent amyloid (florbetaben) and tau (PI‐2620 or MK‐6240) PET MRI, with composite SUVR calculated by averaging key cortical regions. Multivariable linear regression models tested the association of ESS and covariates (GDS, amyloid SUVR, tau SUVR, race) to the three CCI outcome measures (total, non‐amnestic, amnestic). Result: ESS (excessive sleepiness) was significantly positively associated with total CCI (p = 0.01042) as well as non‐amnestic (0.00771) and amnestic CCI subgroups (0.02583), after full covariate adjustment, as was GDS. Race did not show an independent statistically significant association. Conclusion: These results suggest that excessive sleepiness, independent of depression and amyloid and tau burdens, may be a significant contributor to SCD severity. Furthermore, these contributions impact both amnestic and non‐amnestic domains. Future studies are needed to investigate the longitudinal impact of excessive sleepiness on SCD outcomes. [ABSTRACT FROM AUTHOR]

Background: The lateral entorhinal cortex (LEC), followed by area CA1 of hippocampus, are interconnected brain areas implicated early in Alzheimer's disease (AD). Processing of LEC input by CA1 pyramidal neurons (PNs) is critical for non‐spatial memory, in which deficits are seen in early AD. How this process is affected by tauopathy is unclear. Furthermore, CA1 PNs are divided into molecularly and functionally distinct superficial (sPN) and deep (dPN) subpopulations. It is additionally unclear if and how LEC input processing by these subpopulations are differentially impacted. Method: LEC of female PS19 and WT mice (8‐10 month old) were injected with an AAV expressing channelrhodopsin ChrR2. After two weeks, acute hippocampal slices were prepared and whole cell patch clamp recordings were performed on dPNs/sPNs of distal CA1 in current clamp and voltage clamp mode using a potassium‐ or cesium‐based intracellular solution, respectively. Synaptic responses were measured in current clamp and voltage clamp mode, with LEC axons optogenetically activated by blue LED light. In current clamp, excitatory postsynaptic potentials (EPSPs) were measured with inhibition blocked. In voltage clamp, excitatory postsynaptic currents (EPSCs) were evaluated by holding membrane potential at ‐70mV, and inhibitory postsynaptic currents (IPSCs) were evaluated by holding at 0mV. Result: All data is n = 3‐8/group. Compared to WT, LEC‐driven EPSCs showed significant reductions in PS19 sPNs (18.7pA vs. 8.4pA, p = 0.0016) but were unchanged in dPNs (12.4pA vs. 13.6pA, p = 0.2841). Measurements of LEC‐driven EPSPs showed analogous findings. There was no change in paired pulse ratio, ruling out presynaptic changes. There was no change in EPSP decay time constant or temporal summation of the EPSP, ruling out changes in postsynaptic excitability. In contrast to excitation, LEC‐driven IPSCs were unchanged in PS19 versus WT mice in both sPNs (45.7pA vs. 51.9pA, p = 0.62) and dPNs (25.46pA vs. 22.3pA, p = 0.22). Conclusion: LEC drive of CA1 PNs exhibits a cell type‐specific vulnerability to tauopathy, with sPNs differentially susceptible to a reduction of excitation, without changes in feedforward inhibition. Our results further support a postsynaptic mechanism that may be due to spine loss, changes in spine morphology, or shifts in glutamate receptor expression. [ABSTRACT FROM AUTHOR]

Background: How tauopathy disrupts direct entorhinal cortex (EC) inputs to CA1 and their plasticity is understudied, despite its critical role in memory. Moreover, dysfunction of lateral EC (LEC) input is less clear, despite its relevance to early Alzheimer's disease pathogenesis. Here we examined how tau impacts long‐term potentiation (LTP) of LEC→CA1 input in a transgenic model of tauopathy. Method: Acute hippocampal slices were prepared from PS19 and WT mice (8‐10 mo. old, M/F) in which LEC had been injected with an AAV expressing channelrhodopsin ChR2. Ex vivo recordings were achieved with blue LED light to excite LEC axons and an extracellular field electrode in stratum lacunosum moleculare (SLM) of distal CA1 to record field responses. Input‐output curves were established using 25‐100% LED power for field postsynaptic excitatory potentials (fEPSPs) with inhibition blocked (GABAA: 2mm SR95531, GABAB: 1mm CGP55845). LTP of fEPSPs was elicited after a 10" baseline using an LED theta burst stimulation (TBS). Paired pulse ratio (PPR) of fEPSPs was elicited with LED stimulation of 2 pulses at 20Hz. Fluorescence immunohistochemistry (IHC) was performed in separate mice using antibodies to N‐type calcium channels. Result: All results are based on n = 4‐8/sex/genotype. The LEC fEPSP was of reduced magnitude in female PS19 versus WT mice, while unchanged across genotype in male mice. TBS induced a late‐onset LTP (147% at 45") of the LEC fEPSP in female WT mice, which was significantly reduced in female PS19 mice (p = 0.0051). There was no LTP reduction in male mice. LTP in female WT mice was associated with a PPR reduction that was reversed by the addition of the N‐type calcium channel blocker w‐conotoxin GVIA, all of which did not occur in PS19 mice (p<0.0001). PPR was appropriately reduced in male mice across genotype. IHC of N‐type calcium channels showed reduced fluorescence in the SLM of female PS19 mice versus WT. Conclusion: In PS19 mice, the impact of tau on LEC→CA1 input is sex‐dependent, with reduced LEC‐driven excitation and LTP only in female mice. A reduction in presynaptic N‐type calcium channels in PS19 mice may serve as a presynaptic mechanism for the reduced plasticity. [ABSTRACT FROM AUTHOR]

Background: We examined racial differences between measures of limbic white matter tracts and objective sleep parameters in cognitively unimpaired older‐adults. Method: This cross‐sectional study included 170 community‐dwelling cognitively unimpaired older‐adults (mean±SD: age = 67.2±5.2y) participating in NYU studies of sleep, aging, and memory. Subjects completed polysomnography (NPSG) and brain MRI. Sleep measures of interest included total sleep time (TST), NREM stages 2, 3 and REM sleep duration, sleep latency and fragmentation, slow sleep spindles (SSP), sleep spindle density (SPD), AHI4% and REM AHI4%. Microstructural properties of the cingulum, uncinate fasciculus (UF), and fornix were estimated using diffusional tensor imaging (DTI) metrics including radial kurtosis (RK), radial diffusivity (RD), and fractional anisotropy (FA). Adjusted Linear mixed‐effects regression models examined associations between race, sleep, race*sleep and DTI metrics. Result: Participants were 44.1% Black with 16.8±2.5y of education. Subjects were relatively matched on AHI4%, age, BMI and educational level. In the cingulum, increased fragmentation was associated with higher RD β[Left] = 0.0026, p = 0.022), decreased RK (β[Right] = ‐0.0069, p = 0.039) in Blacks. Additionally, increased sleep latency was associated with reduced FA (β[Right] = ‐0.0010, p = 0.019), higher RD (β [Right] = 0.0010, p = 0.008) in Blacks. In the UF, increased fragmentation was associated with higher RD(β[Left] = 0.0052, p = 0.019) and lower RK (β[Right] = ‐0.0010, p = 0.039) in Blacks; increased AHI4%REM was associated with reduced FA β[Left] = 0.0007, p = 0.041), higher RD (β[Right] = ‐0.0007, p = 0.027) and lower RK (β[AHI4%, Left] = ‐0.0029, p = 0.001) in Blacks. Furthermore, higher SSP (βRight] = 0.00031, p = 0.045 and SPD (β[Right] = 0.045, p = 0.025) was associated with higher RK in Blacks. In the cingulum of white participants, higher AHI4%REM was associated with reduced FA β[right] = ‐0.0006, p = 0.013), higher RD β[Left] = 0.0005, p = 0.051), and reduced RK β[Right] = ‐0.00198, p = 0.008). Additionally, NREM stage‐2 sleep duration was associated with higher FA β[Right] = 0.0010, p = 0.037) and higher RK β[Right] = 0.0031, p = 0.040). In the UF, increased fragmentation was associated with reduced RK β[Left] = ‐0.017, p = 0.047) in Whites. Conclusion: Cognitively‐unimpaired Black and White older‐adults showed sleep disruption associations with limbic white matter integrity, with race‐specific associations observed across various microstructural properties of the cingulum, UF, and fornix. Thus, highlighting possible sleep‐related underpinnings of racial differences in Alzheimer disease‐risk. [ABSTRACT FROM AUTHOR]

Introduction: Alzheimer’s disease (AD) and Lewy body disease (LBD) are the two most common neurodegenerative dementias and can occur in combination (AD+LBD). Due to overlapping biomarkers and symptoms, clinical differentiation of these subtypes could be difficult. However, it is unclear how the magnitude of diagnostic uncertainty varies across dementia spectra and demographic variables. We aimed to compare clinical diagnosis and post-mortem autopsy-confirmed pathological results to assess the clinical subtype diagnosis quality across these factors. Methods: We studied data of 1,920 participants recorded by the National Alzheimer’s Coordinating Center from 2005 to 2019. Selection criteria included autopsy-based neuropathological assessments for AD and LBD, and the initial visit with Clinical Dementia Rating (CDR) stage of normal, mild cognitive impairment, or mild dementia. Longitudinally, we analyzed the first visit at each subsequent CDR stage. This analysis included positive predictive values, specificity, sensitivity and false negative rates of clinical diagnosis, as well as disparities by sex, race, age, and education. If autopsy-confirmed AD and/or LBD was missed in the clinic, the alternative clinical diagnosis was analyzed. Findings: In our findings, clinical diagnosis of AD+LBD had poor sensitivities. Over 61% of participants with autopsy-confirmed AD+LBD were diagnosed clinically as AD. Clinical diagnosis of AD had a low sensitivity at the early dementia stage and low specificities at all stages. Among participants diagnosed as AD in the clinic, over 32% had concurrent LBD neuropathology at autopsy. Among participants diagnosed as LBD, 32% to 54% revealed concurrent autopsy-confirmed AD pathology. When three subtypes were missed by clinicians, “No cognitive impairment” and “primary progressive aphasia or behavioral variant frontotemporal dementia” were the leading primary etiologic clinical diagnoses. With increasing dementia stages, the clinical diagnosis accuracy of black participants became significantly worse than other races, and diagnosis quality significantly improved for males but not females. Discussion: These findings demonstrate that clinical diagnosis of AD, LBD, and AD+LBD are inaccurate and suffer from significant disparities on race and sex. They provide important implications for clinical management, anticipatory guidance, trial enrollment and applicability of potential therapies for AD, and promote research into better biomarker-based assessment of LBD pathology. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease and related dementias (AD/ADRD) burden in Costa Rica is expected to become one of the highest in the region. Early detection will help optimize resources and improve primary care interventions. The Montreal Cognitive Assessment (MoCA) has shown good sensitivity for detection of mild cognitive impairment (MCI), but specificity varies depending on the population. This motivates the analysis of different cut‐offs to minimize false‐positive classifications in a Costa Rican sample for its use in clinical settings. Methods: Data was analyzed from 516 memory clinic outpatients (148 cognitively normal, 260 MCI, 108 mild dementia; mean age 66.3 ± 10.8 years) who underwent complete neurological and neuropsychological assessment and were diagnosed by consensus. Optimal MoCA cut‐off scores were identified using the Youden's Index, balanced cut‐offs, and specificity scores. Results: Overall, a cut‐off score of ≥23 showed better accuracy to distinguish between NC and MCI (sensitivity 73%, specificity 83%). When analyzed by educational levels, cut‐off scores of ≥21 showed better accuracy for ≤6 years (sensitivity 80%, specificity 76%), ≥23 for 7‐12 years (sensitivity 86%, specificity 76%) and ≥24 for ≥12 years (sensitivity 70%, specificity 85%). For distinguishing MCI from mild dementia, the optimal overall cut‐off score was ≥15 (sensitivity 65%, specificity 85%). When stratified by years of education, cut‐off scores of ≥14 showed better accuracy for ≤6 years (sensitivity 70%, specificity 88%), ≥15 for 7‐12 years (sensitivity 79%, specificity 95%) and ≥17 for ≥12 years (sensitivity 67%, specificity 93%). Conclusions: A MoCA cut‐off score of ≥23 in Costa Rican population showed better diagnostic accuracy and may reduce the false positive rate. Our findings may be helpful for primary care clinical settings and further referral criteria. Keywords: MoCA, Montreal Cognitive Assessment [ABSTRACT FROM AUTHOR]

High-resolution susceptibility weighted imaging (SWI) provides unique contrast to small venous vasculature. The conspicuity of these mesoscopic veins, such as deep medullary veins in white matter, is subject to change from SWI venography when venous oxygenation in these veins is altered due to oxygenated blood susceptibility changes. The changes of visualization in small veins shows potential to depict regional changes of oxygen utilization and/or vascular density changes in the aging brain. The goal of this study was to use WM venous density to quantify small vein visibility in WM and investigate its relationship with neurodegenerative features, white matter hyperintensities (WMHs), and cognitive/functional status in elderly subjects (N = 137). WM venous density was significantly associated with neurodegeneration characterized by brain atrophy (b = 0.046_ 0.01, p < 0.001), but no significant association was found between WM venous density and WMHs lesion load (p = 0.3963). Further analysis of clinical features revealed a negative trend of WM venous density with the sum-of-boxes of Clinical Dementia Rating and a significant association with category fluency (1-min animal naming). These results suggest that WM venous density on SWI can be used as a sensitive marker to characterize cerebral oxygen metabolism and different stages of cognitive and functional status in neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

The perforant path (PP) carries direct inputs from entorhinal cortex to CA1 pyramidal neurons (PNs), with an impact dependent on PN position across transverse (CA1a-CA1c) and radial (superficial/deep) axes. It remains unclear how aging and Alzheimer disease (AD) affect PP input, despite its critical role in memory and early AD. Applying ex vivo recordings and two-photon microscopy in slices from mice up to 30 months old, we interrogated PP responses across PN subpopulations and compared them to Schaffer collateral and intrinsic excitability changes. We found that aging uniquely impacts PP excitatory responses, abolishing transverse and radial differences via a mechanism independent of presynaptic and membrane excitability change. This is amplified in aged 3xTg-AD mice, with further weakening of PP inputs to CA1a superficial PNs associated with distal dendritic spine loss. This demonstrates a unique feature of aging-related circuit dysfunction, with mechanistic implications related to memory impairment and synaptic vulnerability.

Synaptic spine loss is an early pathophysiologic hallmark of Alzheimer disease (AD) that precedes overt loss of dendritic architecture and frank neurodegeneration. While spine loss signifies a decreased engagement of postsynaptic neurons by presynaptic targets, the degree to which loss of spines and their passive components impacts the excitability of postsynaptic neurons and responses to surviving synaptic inputs is unclear. Using passive multicompartmental models of CA1 pyramidal neurons (PNs), implicated in early AD, we find that spine loss alone drives a boosting of remaining inputs to their proximal and distal dendrites, targeted by CA3 and entorhinal cortex (EC), respectively. This boosting effect is higher in distal versus proximal dendrites and can be mediated by spine loss restricted to the distal compartment, enough to impact synaptic input integration and somatodendritic backpropagation. This has particular relevance to very early stages of AD in which pathophysiology extends from EC to CA1.

In the past decade, much has been elucidated regarding the functional organization of the axonal connection of olfactory sensory neurons to olfactory bulb (OB) glomeruli. However, the manner in which projection neurons of the OB process odorant input and send this information to higher brain centers remains unclear. Here, we report long-range, large-scale tracing of the axonal projection patterns of OB neurons using two-photon microscopy. Tracer injection into a single glomerulus demonstrated widely distributed mitral/tufted cell axonal projections on the lateroventral surface of the mouse brain, including the anterior/posterior piriform cortex (PC) and olfactory tubercle (OT). We noted two distinct groups of labeled axons: PC-orienting axons and OT-orienting axons. Each group occupied distinct parts of the lateral olfactory tract. PC-orienting axons projected axon collaterals to a wide area of the PC but only a few collaterals to the OT. OT-orienting axons densely projected axon collaterals primarily to the anterolateral OT (alOT). Different colored dye injections into the superficial and deep portions of the OB external plexiform layer revealed that the PC-orienting axon populations originated in presumed mitral cells and the OT-orienting axons in presumed tufted cells. These data suggest that although mitral and tufted cells receive similar odor signals from a shared glomerulus, they process the odor information in different ways and send their output to different higher brain centers via the PC and alOT.