scholarly journals Modulation of the rat hippocampal‐cortex network and episodic‐like memory performance following entorhinal cortex stimulation

2021 ◽  
Author(s):  
Yin Jiang ◽  
De‐Feng Liu ◽  
Xin Zhang ◽  
Huan‐Guang Liu ◽  
Chao Zhang ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Memory Performance

scholarly journals Early stages of tau pathology and its associations with functional connectivity, atrophy and memory

Brain ◽  
2021 ◽  
Author(s):  
David Berron ◽  
Jacob W Vogel ◽  
Philip S Insel ◽  
Joana B Pereira ◽  
Long Xie ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Entorhinal Cortex ◽  
Temporal Lobe ◽  
Medial Temporal Lobe ◽  
Memory Impairment ◽  
Memory Performance ◽  
Hippocampal Atrophy ◽  
Tau Pathology ◽  
Β Amyloid ◽  
With Memory

Abstract In Alzheimer’s disease, postmortem studies have shown that the first cortical site where neurofibrillary tangles appear is the transentorhinal region, a subregion within the medial temporal lobe that largely overlaps with area 35, and the entorhinal cortex. Here we used tau-PET imaging to investigate the sequence of tau pathology progression within the human medial temporal lobe and across regions in the posterior-medial system. Our objective was to study how medial temporal tau is related to functional connectivity, regional atrophy, and memory performance. We included 215 β-amyloid negative cognitively unimpaired, 81 β-amyloid positive cognitively unimpaired and 87 β-amyloid positive individuals with mild cognitive impairment, who each underwent [18]F-RO948 tau and [18]F-flutemetamol amyloid PET imaging, structural T1-MRI and memory assessments as part of the Swedish BioFINDER-2 study. First, event-based modelling revealed that the entorhinal cortex and area 35 show the earliest signs of tau accumulation followed by the anterior and posterior hippocampus, area 36 and the parahippocampal cortex. In later stages, tau accumulation became abnormal in neocortical temporal and finally parietal brain regions. Second, in cognitively unimpaired individuals, increased tau load was related to local atrophy in the entorhinal cortex, area 35 and the anterior hippocampus and tau load in several anterior medial temporal lobe subregions was associated with distant atrophy of the posterior hippocampus. Tau load, but not atrophy, in these regions was associated with lower memory performance. Further, tau-related reductions in functional connectivity in critical networks between the medial temporal lobe and regions in the posterior-medial system were associated with this early memory impairment. Finally, in patients with mild cognitive impairment, the association of tau load in the hippocampus with memory performance was partially mediated by posterior hippocampal atrophy. In summary, our findings highlight the progression of tau pathology across medial temporal lobe subregions and its disease-stage specific association with memory performance. While tau pathology might affect memory performance in cognitively unimpaired individuals via reduced functional connectivity in critical medial temporal lobe-cortical networks, memory impairment in mild cognitively impaired patients is associated with posterior hippocampal atrophy.

scholarly journals Paucity of Entorhinal Cortex Pathology of the Alzheimer’s Type in SuperAgers with Superior Memory Performance

2021 ◽  
Author(s):  
Tamar Gefen ◽  
Allegra Kawles ◽  
Beth Makowski-Woidan ◽  
Janessa Engelmeyer ◽  
Ivan Ayala ◽  
...  
Keyword(s):  
Cognitive Impairment ◽  
Entorhinal Cortex ◽  
Memory Performance ◽  
Amyloid Plaques ◽  
Memory Capacity ◽  
Relative Magnitude ◽  
Age Related ◽  
Increased Risk ◽  
Superior Memory ◽  
Normal Controls

Abstract Advancing age is typically associated with declining memory capacity and increased risk of Alzheimer’s disease (AD). Markers of AD such as amyloid plaques (AP) and neurofibrillary tangles (NFTs) are commonly found in the brains of cognitively average elderly but in more limited distribution than in those at the mild cognitive impairment and dementia stages of AD. Cognitive SuperAgers are individuals over age 80 who show superior memory capacity, at a level consistent with individuals 20–30 years their junior. Using a stereological approach, the current study quantitated the presence of AD markers in the memory-associated entorhinal cortex (ERC) of seven SuperAgers compared with six age-matched cognitively average normal control individuals. Amyloid plaques and NFTs were visualized using Thioflavin-S histofluorescence, 6E10, and PHF-1 immunohistochemistry. Unbiased stereological analysis revealed significantly more NFTs in ERC in cognitively average normal controls compared with SuperAgers (P < 0.05) by a difference of ~3-fold. There were no significant differences in plaque density. To highlight relative magnitude, cases with typical amnestic dementia of AD showed nearly 100 times more entorhinal NFTs than SuperAgers. The results suggest that resistance to age-related neurofibrillary degeneration in the ERC may be one factor contributing to preserved memory in SuperAgers.

scholarly journals Cross-sectional associations of tau-PET signal with cognition in cognitively unimpaired adults

Neurology ◽  
2019 ◽  
Vol 93 (1) ◽  
pp. e29-e39 ◽  
Author(s):  
Val J. Lowe ◽  
Tyler J. Bruinsma ◽  
Heather J. Wiste ◽  
Hoon-Ki Min ◽  
Stephen D. Weigand ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Medial Temporal Lobe ◽  
Memory Performance ◽  
Standardized Uptake Value ◽  
Brain Regions ◽  
Population Based ◽  
Cognitive Test ◽  
Amyloid Pet ◽  
Cross Sectional ◽  
Tau Pet

ObjectiveTo assess cross-sectional associations of neurofibrillary tangles, measured by tau-PET, with cognitive performance in cognitively unimpaired (CU) adults.MethodsTau- and amyloid-PET were performed in 579 CU participants aged 50–98 from the population-based Mayo Clinic Study of Aging. Associations between tau-PET signal in 43 brain regions and cognitive test scores were assessed using penalized linear regression. In additional models, participants were classified by normal/abnormal global amyloid-PET (A+/A−) and normal/abnormal regional tau-PET (T+/T−). Regional tau-PET cutpoints were defined as standardized uptake value ratio (SUVR) greater than the 95th percentile of tau-PET SUVR in that region among 117 CU participants aged 30–49.ResultsHigher tau-PET signal was associated with poorer memory performance in all medial temporal lobe (MTL) regions and also in the middle temporal pole and frontal olfactory regions. The largest association with tau-PET and memory z scores was seen in the entorhinal cortex; this association was independent of tau-PET signal in other brain regions. Tau-PET in the entorhinal cortex was also associated with poorer global and language performance. In the entorhinal cortex, T+ was associated with lower memory performance among both A− and A+.ConclusionsTau deposition in MTL regions, as reflected by tau-PET signal, was associated with poorer performance on memory tests in CU participants. The association with entorhinal cortex tau-PET was independent of tau-PET signal in other brain regions. Longitudinal studies are needed to understand the fate of CU participants with elevated medial temporal tau-PET signal.

scholarly journals Entorhinal cortex tau, amyloid-β, cortical thickness and memory performance in non-demented subjects

Brain ◽  
2019 ◽  
Vol 142 (4) ◽  
pp. 1148-1160 ◽  
Author(s):  
David S Knopman ◽  
Emily S Lundt ◽  
Terry M Therneau ◽  
Prashanthi Vemuri ◽  
Val J Lowe ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Cortical Thickness ◽  
Memory Performance ◽  
Verbal Learning ◽  
Amyloid Β ◽  
Gradient Boosting ◽  
Amyloid Pet ◽  
Delayed Recall ◽  
Age Related ◽  
Z Scores

AbstractAs more biomarkers for Alzheimer’s disease and age-related brain conditions become available, more sophisticated analytic approaches are needed to take full advantage of the information they convey. Most work has been done using categorical approaches but the joint relationships of tau PET, amyloid PET and cortical thickness in their continuous distributions to cognition have been under-explored. We evaluated non-demented subjects over age 50 years in the Mayo Clinic Study of Aging, 2037 of whom had undergone 3 T MRI scan, 985 amyloid PET scan with 11C-Pittsburgh compound B (PIB) and MRI, and 577 PIB-PET, 18F-AV1451 flortaucipir PET and MRI. Participants received a nine-test cognitive battery. Three test scores (logical memory delayed recall, visual reproduction delayed recall and auditory verbal learning test delayed recall) were used to generate a memory composite z-score. We used Gradient Boosting Machine models to analyse the relationship between regional cortical thickness, flortaucipir PET signal, PIB-PET signal and memory z-scores. Age, education, sex and number of test exposures were included in the model as covariates. In this population-based study of non-demented subjects, most of the associations between biomarkers and memory z-scores accrued after 70 years of age. Entorhinal cortex exhibited the strongest associations between biomarkers and memory z-scores. Other temporal regions showed similar but attenuated associations, and non-temporal regions had negligible associations between memory z-scores and biomarkers. Entorhinal flortaucipir PET signal, PIB-PET signal and entorhinal cortical thickness were independently and additively associated with declining memory z-scores. In contrast to global PIB-PET signal where only very high amyloid-β levels were associated low memory z-scores, entorhinal flortaucipir PET signal just above background levels was associated with low memory z-scores. The lowest memory z-scores occurred with the confluence of elevated entorhinal flortaucipir PET signal and lower entorhinal cortical thickness.

scholarly journals The olfactory bulb modulates entorhinal cortex oscillations during spatial working memory

2021 ◽  
Vol 71 (1) ◽  
Author(s):  
Morteza Salimi ◽  
Farhad Tabasi ◽  
Milad Nazari ◽  
Sepideh Ghazvineh ◽  
Alireza Salimi ◽  
...  
Keyword(s):  
Working Memory ◽  
Olfactory Bulb ◽  
Entorhinal Cortex ◽  
Spatial Working Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Low Frequency ◽  
Rhythmic Activity ◽  
Brain Regions ◽  
Simultaneous Recording

AbstractCognitive functions such as working memory require integrated activity among different brain regions. Notably, entorhinal cortex (EC) activity is associated with the successful working memory task. Olfactory bulb (OB) oscillations are known as rhythms that modulate rhythmic activity in widespread brain regions during cognitive tasks. Since the OB is structurally connected to the EC, we hypothesized that OB could modulate EC activity during working memory performance. Herein, we explored OB–EC functional connectivity during spatial working memory performance by simultaneous recording local field potentials when rats performed a Y-maze task. Our results showed that the coherence of delta, theta, and gamma-band oscillations between OB and EC was increased during correct trials compared to wrong trials. Cross-frequency coupling analyses revealed that the modulatory effect of OBs low-frequency phase on EC gamma power and phase was enhanced when animals correctly performed working memory task. The influx of information from OB to EC was also increased at delta and gamma bands within correct trials. These findings indicated that the modulatory influence of OB rhythms on EC oscillations might be necessary for successful working memory performance.

P4-299: TAU ACCUMULATION IN THE ENTORHINAL CORTEX AND PRECUNEUS IS ASSOCIATED WITH CORTICAL AMYLOID-BETA BURDEN, AGE AND WORSE MEMORY PERFORMANCE IN PRECLINICAL AUTOSOMAL DOMINANT ALZHEIMER'S DISEASE

2006 ◽  
Vol 14 (7S_Part_30) ◽  
pp. P1567-P1567
Author(s):  
Yakeel T. Quiroz ◽  
Reisa A. Sperling ◽  
Francisco Lopera ◽  
Ana Baena ◽  
Sergio Alvarez ◽  
...  
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Entorhinal Cortex ◽  
Amyloid Beta ◽  
Autosomal Dominant ◽  
Memory Performance ◽  
Autosomal Dominant Alzheimer’S Disease

scholarly journals Reduced Cognitive Performance in Aged Rats Correlates with Increased Excitation/Inhibition Ratio in the Dentate Gyrus in Response to Lateral Entorhinal Input

2019 ◽  
Author(s):  
Trinh Tran ◽  
Michelle Bridi ◽  
Ming Teng Koh ◽  
Michela Gallagher ◽  
Alfredo Kirkwood
Keyword(s):  
Dentate Gyrus ◽  
Entorhinal Cortex ◽  
Medial Temporal Lobe ◽  
Granule Cells ◽  
Memory Performance ◽  
Pyramidal Cells ◽  
Excitatory Input ◽  
Inhibitory Interneurons ◽  
Aged Rats ◽  
Anatomical Studies

ABSTRACTAging often impairs cognitive functions associated with the medial temporal lobe (MTL). Anatomical studies identified the layer II pyramidal cells of the lateral entorhinal cortex (LEC) as one of the most vulnerable elements within the MTL. These cells provide a major excitatory input to the dentate gyrus hippocampal subfield by synapsing onto granule cells and onto local inhibitory interneurons, and a fraction of these contacts are lost in aged individuals with impaired learning. Using optogenetics we evaluated the functional status of the remaining inputs in an outbred rat model of aging that distinguishes between learning impaired and learning unimpaired individuals. We found that aging affects the pre- and postsynaptic strength of the LEC inputs onto granule cells. However, the magnitude these changes was similar in impaired and un-impaired rats. In contrast, the recruitment of inhibition by LEC activation was selectively reduced in the aged impaired subjects. These findings are consistent with the notion that the preservation of an adequate balance of excitation and inhibition is crucial for maintain proficient memory performance during aging.

scholarly journals Medial Temporal Tau Pathology Is Associated With Verbal Memory

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 767-767
Author(s):  
Murat Bilgel ◽  
Jacob Ziontz ◽  
Andrea Shafer ◽  
Luigi Ferrucci ◽  
Dean Wong ◽  
...  
Keyword(s):  
Entorhinal Cortex ◽  
Verbal Memory ◽  
Memory Performance ◽  
Cognitive Status ◽  
Therapeutic Interventions ◽  
Tau Pathology ◽  
Cognitively Normal ◽  
Positron Emission ◽  
Normal Individuals ◽  
Baltimore Longitudinal Study

Abstract Medial temporal tau pathology is frequently observed in individuals over 70 regardless of cognitive status. To understand the link between tau and cognitive performance, we evaluated tau pathology using 18F-flortaucipir positron emission tomography among 95 cognitively normal participants from the Baltimore Longitudinal Study of Aging. We examined tau levels in early Braak regions (entorhinal cortex and hippocampus) in relation to verbal episodic memory performance concurrent with and prior to the tau scan using linear mixed effects models adjusted for age, sex, amyloid status, and time from PET scan. Higher hippocampal tau burden had a trend-level association with lower concurrent memory performance (p=0.05). Greater tau pathology in the hippocampus and entorhinal cortex was associated with steeper decline in memory performance prior to tau scan (p=0.013 and 0.026, respectively). These findings suggest that therapeutic interventions targeting tau pathology may need to be administered early among cognitively normal individuals to prevent memory decline.

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