55 research outputs found
Memory for public events in mild cognitive impairment and Alzheimerâs disease : the importance of rehearsal
Ribotâs law refers to the better preservation of remote memories compared with recent ones that presumably characterizes retrograde amnesia. Even if Ribot-type temporal gradient has been extensively studied in retrograde amnesia, particularly in Alzheimerâs disease (AD), this pattern has not been consistently found. One explanation for these results may be that rehearsal frequency rather than remoteness accounts for the better preservation of these memories. Thus, the aim of present study was to address this question by studying retrograde semantic memory in subjects with amnestic mild cognitive impairment (aMCI) (nâ=â20), mild AD (nâ=â20) and in healthy older controls (HC; nâ=â19). In order to evaluate the impact of repetition as well as the impact of remoteness, we used a test assessing memory for enduring and transient public events that occurred in the recent and remote past. Results show no clear temporal gradient across time periods (1960â1975; 1976â1990; 1991â2005; 2006â2011), but a better performance was observed in all three groups for enduring compared with transient events. Moreover, although deficits were globally found in both patients groups compared with HC, more specific analyses revealed that aMCI patients were only impaired on transient events while AD patients were impaired on both transient and enduring events. Exploratory analyses also revealed a tendency suggesting preservation of remote transient events in aMCI. These findings are discussed with regards to memory consolidation models
The impact of time and repeated exposure on famous person knowledge in amnestic Mild cognitive impairment and Alzheimerâs disease
Objective: Famous people knowledge has been shown to be impaired early in Alzheimerâs disease (AD) and amnestic mild cognitive impairment (aMCI). However, the question of whether recently acquired knowledge is more impaired than remotely acquired knowledge remains a matter of debate. The aim of this study was to investigate the patterns of semantic memory impairment in aMCI and AD by investigating two factors that may influence the retrieval of such knowledge, namely remoteness and frequency of repetition of information over time. Method: Three groups (19 controls, 20 aMCI and 20 AD patients) were compared on a test assessing general and specific biographical knowledge about famous people, where the period of acquired fame (remote vs recent) and the type of fame (enduring vs transient) were controlled for. Results: Global performance of aMCI and AD patients was significantly poorer than that of controls. However, different patterns of recall were observed as a function of time and type of fame. A temporal gradient was found in both patient groups for enduring names but not for transient ones, whereby knowledge about remote enduring famous persons was better recalled. Patients were more impaired at questions assessing specific biographical knowledge (unique to an individual) than more general knowledge. Conclusions: Tests of famous people knowledge offer a unique opportunity to investigate semantic deficits in aMCI and AD, because they make it possible to estimate the time at which memories were acquired, as well as the type of fame. Results are discussed in light of memory consolidation models.
Keywords
Purine Homeostasis Is Necessary for Developmental Timing, Germline Maintenance and Muscle Integrity in Caenorhabditis elegans
International audiencePurine homeostasis is ensured through a metabolic network widely conserved from prokaryotes to humans. Purines can either be synthesized de novo, reused, or produced by interconversion of extant metabolites using the so-called recycling pathway. Although thoroughly characterized in microorganisms, such as yeast or bacteria, little is known about regulation of the purine biosynthesis network in metazoans. In humans, several diseases are linked to purine metabolism through as yet poorly understood etiologies. Particularly, the deficiency in adenylosuccinate lyase (ADSL)-an enzyme involved both in the purine de novo and recycling pathways-causes severe muscular and neuronal symptoms. In order to address the mechanisms underlying this deficiency, we established Caenorhabditis elegans as a metazoan model organism to study purine metabolism, while focusing on ADSL. We show that the purine biosynthesis network is functionally conserved in C. elegans. Moreover, adsl-1 (the gene encoding ADSL in C. elegans) is required for developmental timing, germline stem cell maintenance and muscle integrity. Importantly, these traits are not affected when solely the de novo pathway is abolished, and we present evidence that germline maintenance is linked specifically to ADSL activity in the recycling pathway. Hence, our results allow developmental and tissue specific phenotypes to be ascribed to separable steps of the purine metabolic network in an animal model
LâĂ©valuation de la mĂ©moire rĂ©trograde dans la population quĂ©bĂ©coise ĂągĂ©e: Le PUB-40 et le PUB-12
LâĂ©valuation de la mĂ©moire reprĂ©sente une partie importante du travail des neuropsychologues
cliniciens Ćuvrant en gĂ©riatrie. En effet, au Canada, environ le tiers des aĂźnĂ©s rapporte une
plainte mnĂ©sique dont les causes sont variĂ©es. Selon lâĂ©tiologie, diffĂ©rentes composantes du
systĂšme mnĂ©sique peuvent ĂȘtre atteintes, toutefois, lâĂ©valuation de la mĂ©moire rĂ©trograde non
autobiographique (publique ou sĂ©mantique) nâest souvent effectuĂ©e que de maniĂšre superficielle,
puisquâaucun outil dâĂ©valuation fiable, valide et standardisĂ© nâest disponible pour la population
quĂ©bĂ©coise vieillissante. Les objectifs de cette recherche Ă©taient donc (1) dâĂ©laborer un protocole
dâĂ©valuation de la mĂ©moire rĂ©trograde non autobiographique spĂ©cifiquement adaptĂ© Ă cette
population, le PUB-40, (2) de recueillir des données de référence auprÚs de 105 participants
ùgés sains et (3) de développer une version abrégée à partir des items permettant de discriminer
un groupe de 20 patients atteints de troubles cognitifs légers de type amnésique (TCLa) des
participants ùgés sains
Responses to hydric stress in the seed-borne necrotrophic fungus Alternaria brassicicola
Alternaria brassicicola is a necrotrophic fungus causing black spot disease and is an economically important seed-borne pathogen of cultivated brassicas. Seed transmission is a crucial component of its parasitic cycle as it promotes long-term survival and dispersal. Recent studies, conducted with the Arabidopsis thaliana/A. brassicicola pathosystem, showed that the level of susceptibility of the fungus to water stress strongly influenced its seed transmission ability. In this study, we gained further insights into the mechanisms involved in the seed infection process by analyzing the transcriptomic and metabolomic responses of germinated spores of A. brassicicola exposed to water stress. Then, the repertoire of putative hydrophilins, a group of proteins that are assumed to be involved in cellular dehydration tolerance, was established in A. brassicicola based on the expression data and additional structural and biochemical criteria. Phenotyping of single deletion mutants deficient for fungal hydrophilin-like proteins showed that they were affected in their transmission to A. thaliana seeds, although their aggressiveness on host vegetative tissues remained intact
COVID-19 symptoms at hospital admission vary with age and sex: results from the ISARIC prospective multinational observational study
Background:
The ISARIC prospective multinational observational study is the largest cohort of hospitalized patients with COVID-19. We present relationships of age, sex, and nationality to presenting symptoms.
Methods:
International, prospective observational study of 60â109 hospitalized symptomatic patients with laboratory-confirmed COVID-19 recruited from 43 countries between 30 January and 3 August 2020. Logistic regression was performed to evaluate relationships of age and sex to published COVID-19 case definitions and the most commonly reported symptoms.
Results:
âTypicalâ symptoms of fever (69%), cough (68%) and shortness of breath (66%) were the most commonly reported. 92% of patients experienced at least one of these. Prevalence of typical symptoms was greatest in 30- to 60-year-olds (respectively 80, 79, 69%; at least one 95%). They were reported less frequently in children (â€â18 years: 69, 48, 23; 85%), older adults (â„â70 years: 61, 62, 65; 90%), and women (66, 66, 64; 90%; vs. men 71, 70, 67; 93%, each Pâ<â0.001). The most common atypical presentations under 60 years of age were nausea and vomiting and abdominal pain, and over 60 years was confusion. Regression models showed significant differences in symptoms with sex, age and country.
Interpretation:
This international collaboration has allowed us to report reliable symptom data from the largest cohort of patients admitted to hospital with COVID-19. Adults over 60 and children admitted to hospital with COVID-19 are less likely to present with typical symptoms. Nausea and vomiting are common atypical presentations under 30 years. Confusion is a frequent atypical presentation of COVID-19 in adults over 60 years. Women are less likely to experience typical symptoms than men
Real-time hand motion recognition using sEMG Patterns Classification
Increasing
performance while decreasing the
cost of sEMG prostheses is an important milestone in
rehabilitation engineering. The
different types of
prosthetic
hands that are currently available to patients worldwide
can
benefit from more
effective and intuitive control. This paper
presents a real
-time approach to classify finger motions based
on surface electromyography (sEMG) signals. A multichannel
signal acquisition platform implemented using components of
f
the shelf is use
d to record
forearm sEMG signals
from 7
channels. sEMG pattern classification is performed in real
time, using a Linear Discriminant Analysis approach. Thirteen
hand motions can be successfully identified with an accuracy of
up to 95.
8% and
of
92.
7%
on average
for
8 participants, with
an updated prediction every 192 ms
High dream recall frequency is associated with an increase of both bottom-up and top-down attentional processes
International audienceAbstract Event-related potentials (ERPs) associated with the involuntary orientation of (bottom-up) attention toward an unexpected sound are of larger amplitude in high dream recallers (HR) than in low dream recallers (LR) during passive listening, suggesting different attentional functioning. We measured bottom-up and top-down attentional performance and their cerebral correlates in 18 HR (11 women, ageâ=â22.7Â years, dream recall frequencyâ=â5.3Â days with a dream recall per week) and 19 LR (10 women, ageâ=â22.3, DRFâ=â0.2) using EEG and the Competitive Attention Task. Between-group differences were found in ERPs but not in behavior. The results show that HR present larger ERPs to distracting sounds than LR even during active listening, arguing for enhanced bottom-up processing of irrelevant sounds. HR also presented larger contingent negative variation during target expectancy and P3b to target sounds than LR, speaking for an enhanced recruitment of top-down attention. The attentional balance seems preserved in HR since their performances are not altered, but possibly at a higher resource cost. In HR, increased bottom-up processes would favor dream recall through awakening facilitation during sleep and enhanced top-down processes may foster dream recall through increased awareness and/or short-term memory stability of dream content
Aerobic respiration and hypoxia in the lower st. lawrence estuary: Stable isotope ratios of dissolved oxygen constrain oxygen sink partitioning
We measured the concentration and the stable isotope ratios of dissolved oxygen in the water column in the Estuary and Gulf of St. Lawrence to determine the relative importance of pelagic and benthic dissolved oxygen respiration to the development of hypoxic deep waters. The progressive landward decrease of dissolved oxygen in the bottom waters along the axis of the Laurentian Channel (LC) is accompanied by an increase in the 18O : 16O ratio, as would be expected from O-isotope fractionation associated with bacterial oxygen respiration. The apparent O-isotope effect, ΔO-app, of 10.8% reveals that community O-isotope fractionation is significantly smaller than if bacterial respiration occurred solely in the water column. Our observation can best be explained by a contribution of benthic O2 consumption occurring with a strongly reduced O-isotope effect at the scale of sediment-water exchange (ΔO-sed, 7%). The value for ΔO-sed was estimated from benthic O 2 exchange simulations using a one-dimensional diffusion-reaction O-isotope model. Adopting this ΔO-sed value, and given the observed community O-isotope fractionation, we calculate that approximately two thirds of the ecosystem respiration occurs within the sediment, in reasonable agreement with direct respiration measurements. Based on the difference between dissolved oxygen concentrations in the deep waters of the Lower St. Lawrence Estuary and in the water that enters the LC at Cabot Strait, we estimate an average respiration rate of 5500 mmol O 2 m -2 yr -1 for the 100-m-thick layer of bottom water along the LC, 3540 mmol O 2 m -2 yr -1 of which is attributed to bacterial benthic respiration.Link_to_subscribed_fulltex
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