Measuring cortical connectivity in Alzheimer's disease as a brain neural network pathology: Toward clinical applications

Objectives: The objective was to review the literature on diffusion tensor imaging as well as resting-state functional magnetic resonance imaging and electroencephalography (EEG) to unveil neuroanatomical and neurophysiological substrates of Alzheimer’s disease (AD) as a brain neural network pathology affecting structural and functional cortical connectivity underlying human cognition. Methods: We reviewed papers registered in PubMed and other scientific repositories on the use of these techniques in amnesic mild cognitive impairment (MCI) and clinically mild AD dementia patients compared to cognitively intact elderly individuals (Controls). Results: Hundreds of peer-reviewed (cross-sectional and longitudinal) papers have shown in patients with MCI and mild AD compared to Controls (1) impairment of callosal (splenium), thalamic, and anterior–posterior white matter bundles; (2) reduced correlation of resting state blood oxygen level-dependent activity across several intrinsic brain circuits including default mode and attention-related networks; and (3) abnormal power and functional coupling of resting state cortical EEG rhythms. Clinical applications of these measures are still limited. Conclusions: Structural and functional (in vivo) cortical connectivity measures represent a reliable marker of cerebral reserve capacity and should be used to predict and monitor the evolution of AD and its relative impact on cognitive domains in pre-clinical, prodromal, and dementia stages of AD. (JINS, 2016, 22, 138–163

Collective Resistance in Microbial Communities by Intracellular Antibiotic Deactivation.

The structure and composition of bacterial communities can compromise antibiotic efficacy. For example, the secretion of β-lactamase by individual bacteria provides passive resistance for all residents within a polymicrobial environment. Here, we uncover that collective resistance can also develop via intracellular antibiotic deactivation. Real-time luminescence measurements and single-cell analysis demonstrate that the opportunistic human pathogen Streptococcus pneumoniae grows in medium supplemented with chloramphenicol (Cm) when resistant bacteria expressing Cm acetyltransferase (CAT) are present. We show that CAT processes Cm intracellularly but not extracellularly. In a mouse pneumonia model, more susceptible pneumococci survive Cm treatment when coinfected with a CAT-expressing strain. Mathematical modeling predicts that stable coexistence is only possible when antibiotic resistance comes at a fitness cost. Strikingly, CAT-expressing pneumococci in mouse lungs were outcompeted by susceptible cells even during Cm treatment. Our results highlight the importance of the microbial context during infectious disease as a potential complicating factor to antibiotic therapy

Scientific Bases for a Participatory Forest Landscape Management

In Madagascar – a biodiversity hotspot of international importance – the villagers depend on the forest first for its soil as a reserve of arable land as well as a shelter and a pasture for the herds, and second for the production of timber, charcoal and other forest products. Most of the currently proposed conservation management systems for forests do not take into consideration villagers’ needs, in Madagascar too; indeed degradation and deforestation have continuously occurred in places where the forest is under great pressure. In targeting the improvement of the livelihood of local populations and the maintenance of “multifunctionality”, especially the ecological value of the forest, the present project aims at developing scientific criteria for a sustainable management of forest landscapes in western Madagascar at a regional scale. A detailed inventory of resources and a specific understanding of stakeholder requirements and strategies will allow drawing an accurate picture of the human-forest interface. A participatory approach paves the way for realistic management criteria that are really adequate to the ecological and social situations. The management criteria will provide a tool for further discussions on landscape management in central Menabe

Who wants to conserve remaining forest fragments in the Manompana corridor?

Contiguous forests in Madagascar are continuously converted into forest fragments due to deforestation, and dispersed into landscape mosaics dominated by agriculture. These fragments are of increasing importance for biodiversity conservation as well as for the well being of rural inhabitants, providing a high diversity of timber and non - timber forest products. An increasing number of international projects are therefore trying to preserve remaining forests and to transfer the management of these forests to local communities. However, it is not known how important the preservation of forest fragments are to local people. We therefore explore the importance of forest fragments as a source of cash income to different groups separated by wealth level and access to forest resources. A multi - method research approach was taken, based on score application exercises as well as interviews with individual households and focus groups. Our study site was located at the east coast of Madagascar in the Manompana corridor. Results show that some groups are significantly more interested in the preservation of forest fragments than others. Interest is significantly related to the wealth of local inhabitants as well as to the walking distance between villages and forest resources. Nevertheless, interest in resource preservation does not depend on how important fragments are to local people, but rather on the awareness about resource scarcity

Recommandations pour une agriculture plus écologique respectant les besoins socio - écono-miques locaux, région du Menabe Central, côte ouest de Madagascar

Dans le Menabe Central (côte ouest de Madagascar), les paysages forestiers deviennent toujours plus ouverts, le taux de déforestation avoisinant les 0,7 % . La déforestation étant notamment due à des défrichements pour l’agriculture qui est la principale activité de la région, une gestion agricole écologiquement durable apparaît comme une nécessité urgente. Afin de ne pas défavoriser les populations locales vivant dans des conditions socio-économiques difficiles (81,3 % de la population malgache vivait encore en - dessous du seuil de pauvreté en 2010), cet aménagement agricole doit également viser à proposer des  recommandations socio - économiquement rentables. Cette étude vise donc à confirmer l’hypothèse selon laquelle une agriculture plus écologique – permettant aux agriculteurs de se sédentariser sur leurs terres et diminuant les défrichements forestiers – qui fournirait des produits économiquement rentables sur le long terme répondrait aux nécessités socio-économiques et écologiques locales. La présente étude conclut en mettant en évidence quatre recommandations : i) La riziculture devrait être privilégiée ; ii) les techniques agro - forestières et les utilisations de fertilisants naturels devraient être encouragées ; iii) des alternatives permettant de diversifier le revenu des populations rurales, telle que la rizipisciculture, devraient être soutenues ; et iv) un aménagement des surfaces sylvicoles défrichées devrait être mis en place de manière participative.In the Central Menabe region on the west cost of Madagascar, traditional uses of forest resources create an increasingly open landscape. The current annual rate of loss of Malagasy dense dry forest, the natural forest type of the region, is 0.7 % . Agriculture represents the principal activity of people in Central Menabe, and the main reason for the decrease in forest cover. In the current difficult socio-economical context (81.3 % of the Malagasy population lived under the poverty line in 2010), where a threat to dry forests clearly exists, it is therefore urgent to propose scientifically-sound and participatory recommendations for ecologically sustainable and socio - economically profitable agricultural use of the Central Menabe landscape. The objective of this study is to confirm the hypothesis that a more sustainable form of agriculture – promoting farmers’ permanent use of cultivated fields – would generate high value economic products, and contribute to the socio - economic and environmental needs of the region. To meet this objective, the study answers three research questions: i) What are the principal products of the villager economy? ii) what is the role of traditional agriculture in deforestation?; and, iii) what is the potential for, and the expectations of the local populations towards, more sedentary agricultural techniques? The research uses methods from both social (scoring and questionnaires) and natural sciences (inventories and measures of clearings), and was carried out in six villages representative of the Central Menabe region. Two villages mainly practiced rice cultivation, two mainly carried out slash and burn cultivation (of maize, cassava and peanut), and two practiced both slash and burn and rice cultivation. Half of the villages were situated near a national road and have thus an easy access to regional markets; the three other villages were more remote. In total 120 inhabitants were involved in 72 different scoring exercises and 288 participated in a questionnaire survey. Mann-Whitney and chi - square tests were used to test for statistical significance in observed differences.Analyses confirm that rice is the main pillar of the villager economy in the region, and that – at the village scale – this product serves a strong commercial demand which is not always satisfied. Farmers take a weak interest in the consumption of products from slash and burn cultivation (low demand), although the majority of people that cultivate maize, cassava or peanut perceive slash and burn cultivation as a source of alimentary or financial security (subsistence or sale). Give

Distinctive correspondence between separable visual attention functions and intrinsic brain networks

Separable visual attention functions are assumed to rely on distinct but interacting neural mechanisms. Bundesen's “theory of visual attention” (TVA) allows the mathematical estimation of independent parameters that characterize individuals' visual attentional capacity (i.e., visual processing speed and visual short-term memory storage capacity) and selectivity functions (i.e., top-down control and spatial laterality). However, it is unclear whether these parameters distinctively map onto different brain networks obtained from intrinsic functional connectivity, which organizes slowly fluctuating ongoing brain activity. In our study, 31 demographically homogeneous healthy young participants performed whole- and partial-report tasks and underwent resting-state functional magnetic resonance imaging (rs-fMRI). Report accuracy was modeled using TVA to estimate, individually, the four TVA parameters. Networks encompassing cortical areas relevant for visual attention were derived from independent component analysis of rs-fMRI data: visual, executive control, right and left frontoparietal, and ventral and dorsal attention networks. Two TVA parameters were mapped on particular functional networks. First, participants with higher (vs. lower) visual processing speed showed lower functional connectivity within the ventral attention network. Second, participants with more (vs. less) efficient top-down control showed higher functional connectivity within the dorsal attention network and lower functional connectivity within the visual network. Additionally, higher performance was associated with higher functional connectivity between networks: specifically, between the ventral attention and right frontoparietal networks for visual processing speed, and between the visual and executive control networks for top-down control. The higher inter-network functional connectivity was related to lower intra-network connectivity. These results demonstrate that separable visual attention parameters that are assumed to constitute relatively stable traits correspond distinctly to the functional connectivity both within and between particular functional networks. This implies that individual differences in basic attention functions are represented by differences in the coherence of slowly fluctuating brain activity

Dynamic association between perfusion and white matter integrity across time since injury in Veterans with history of TBI.

ObjectiveCerebral blood flow (CBF) plays a critical role in the maintenance of neuronal integrity, and CBF alterations have been linked to deleterious white matter changes. Although both CBF and white matter microstructural alterations have been observed within the context of traumatic brain injury (TBI), the degree to which these pathological changes relate to one another and whether this association is altered by time since injury have not been examined. The current study therefore sought to clarify associations between resting CBF and white matter microstructure post-TBI.Methods37 veterans with history of mild or moderate TBI (mmTBI) underwent neuroimaging and completed health and psychiatric symptom questionnaires. Resting CBF was measured with multiphase pseudocontinuous arterial spin labeling (MPPCASL), and white matter microstructural integrity was measured with diffusion tensor imaging (DTI). The cingulate cortex and cingulum bundle were selected as a priori regions of interest for the ASL and DTI data, respectively, given the known vulnerability of these regions to TBI.ResultsRegression analyses controlling for age, sex, and posttraumatic stress disorder (PTSD) symptoms revealed a significant time since injury × resting CBF interaction for the left cingulum (p < 0.005). Decreased CBF was significantly associated with reduced cingulum fractional anisotropy (FA) in the chronic phase; however, no such association was observed for participants with less remote TBI.ConclusionsOur results showed that reduced CBF was associated with poorer white matter integrity in those who were further removed from their brain injury. Findings provide preliminary evidence of a possible dynamic association between CBF and white matter microstructure that warrants additional consideration within the context of the negative long-term clinical outcomes frequently observed in those with history of TBI. Additional cross-disciplinary studies integrating multiple imaging modalities (e.g., DTI, ASL) and refined neuropsychiatric assessment are needed to better understand the nature, temporal course, and dynamic association between brain changes and clinical outcomes post-injury