Subjects with mild cognitive impairment are at risk of developing Alzheimer's disease. Cognitive stimulation is an emerging intervention in the field of neurology and allied sciences, having already ...been shown to improve cognition in subjects with mild cognitive impairment. Yet no studies have attempted to unravel the brain mechanisms that support such improvement. This study uses functional magnetic resonance imaging to measure the effect of memory training on brain activation in older adults with mild cognitive impairment and to assess whether it can reverse the brain changes associated with mild cognitive impairment. Brain activation associated with verbal encoding and retrieval was recorded twice prior to training and once after training. In subjects with mild cognitive impairment, increased activation was found after training within a large network that included the frontal, temporal and parietal areas. Healthy controls showed mostly areas of decreased activation following training. Comparison with pre-training indicated that subjects with mild cognitive impairment used a combination of specialized areas; that is, areas activated prior to training and new alternative areas activated following training. However, only activation of the right inferior parietal lobule, a new area of activation, correlated with performance. Furthermore, the differences between the brain activation patterns of subjects with mild cognitive impairment and those of healthy controls were attenuated by training in a number of brain regions. These results indicate that memory training can result in significant neural changes that are measurable with brain imaging. They also show that the brains of people with mild cognitive impairment remain highly plastic.
Background Alzheimer's disease is a neurodegenerative disease with progressive cognitive impairments that are likely to affect the compensatory mechanisms and the cerebral activation patterns of the ...patients. Methods Functional neuroimaging was used to test the effect of disease severity on the brain activation of persons at risk for Alzheimer's disease and to highlight the process of compensation in some of these individuals. This was done for the verbal learning of either semantically related or semantically unrelated word pairs. Twenty-six persons with mild cognitive impairment (MCI) were separated into two groups, MCI higher-cognition and MCI lower-cognition, with a split-median on their scores for the Mattis Dementia Rating Scale. A group of 14 healthy older adults were matched to the MCI participants. Results In both task conditions, MCI higher-cognition activated additional regions, relative to control subjects, in the right ventrolateral and dorsolateral prefrontal brain areas. Additional areas of hyperactivation were found in the right prefrontal area 45 when encoding semantically related word pairs and in the left hippocampus during encoding of unrelated word pairs. In contrast, MCI lower-cognition failed to show additional prefrontal activations when compared with healthy control subjects and showed decreased activation in posterior areas. Conclusions These results are in line with compensation occurring at the beginning of the MCI continuum and with the breakdown of compensation in patients experiencing more severe symptoms.
Our goal was to test the effect of disease severity on the brain activation associated with two executive processes: manipulation and divided attention.
This was achieved by administrating a ...manipulation task and a divided attention task using functional magnetic resonance imaging to 24 individuals with mild cognitive impairment (MCI) and 14 healthy controls matched for age, sex and education. The Mattis Dementia Rating Scale was used to divide persons with MCI into those with better and worse cognitive performances.
Both tasks were associated with more brain activation in the MCI group with higher cognition than in healthy controls, particularly in the left frontal areas. Correlational analyses indicated that greater activation in a frontostriatal network hyperactivated by the higher-cognition group was related with better task performance, suggesting that these activations may support functional reorganization of a compensatory nature. By contrast, the lower-cognition group failed to show greater cerebral hyperactivation than controls during the divided attention task and, during the manipulation task, and showed less brain activation than controls in the left ventrolateral cortex, a region commonly hypoactivated in patients with Alzheimer’s disease.
These findings indicate that, during the early phase of MCI, executive functioning benefits from neural reorganization, but that a breakdown of this brain plasticity characterizes the late stages of MCI.
•Landscape configuration accounted for 48% of the total variation in water quality.•The individual contribution of landscape configuration factors was 6.2%.•A forest cover >47% is required to prevent ...the eutrophication of Canadian streams.•In areas of intensive farming, high landscape diversity improves water quality.•Woodlands with a complex shape (edge density >36m/ha) benefit water quality.
It is well known that the composition of land cover within a watershed plays a large role in regulating stream water quality. However, there remains significant uncertainty regarding the effect of spatial configuration of different types of land cover on water quality. Using periphytic algae (diatoms) as indicators of stream trophic state, we investigated the relationship between landscape configuration and water quality in a large number of watersheds (590) at varying catchment scales in Eastern Canada. Variation partitioning analysis showed that landscape configuration explained 48% of the variation in water quality. However, since the physiographic setting constrains most agricultural activities, most of the variation was attributed to the shared influence of surficial deposits, land cover and landscape configuration (34%). The results from regression models showed that the geomorphological setting of watersheds (surficial deposits and slopes) and the proportion of different land cover types (mainly forests, wetlands, crops and urban areas) have a major impact on stream water quality. Nevertheless, a few configuration metrics emerged as important factors. Landscape diversity appeared to have a negative impact on water quality, whereas forest and wetland edge densities had a positive impact. Moreover, the influence of these lanscape metrics seems to occur at certain thresholds. In areas of intensive farming, streams with a forest area that covers at least 47% of the watershed have a better water quality. Below this threshold, eutrophic and meso-eutrophic conditions are more frequent in streams and rivers. The shape and location of forested patches were also found to be relevant. Woodlands and wetlands with an edge density higher than 36m/ha and located along streams and gullies have a positive impact on water quality. For the same proportion of forest, complex patches will be more efficient filters than large regular patches. Forest edge density seems to control the extent of the interface with the agricultural sources and thus promotes the “sink” effect of forests on nutrients.
Hyperactivation, which is defined as a higher level of activation in patients compared to cognitively unimpaired older adults (controls; CTL), might represent an early signature of Alzheimer's ...Disease (AD). The goal of this study was to assess the presence and location of hyperactivation in individuals with mild cognitive impairment (MCI) who were later diagnosed with dementia, examine how hyperactivation changes longitudinally, and whether it is related to time before dementia. Forty participants, 26 with MCI and 14 CTL were enrolled in the study. Magnetic resonance imaging was used to measure functional activation while participants encoded word-pairs as well as cortical thickness and regional brain volume at study entry (Y0) and two years later (Y2). Clinical follow-up was completed every two years following study entry to identify progressors (pMCI), that is, individuals who later received a diagnosis of dementia. Task-related activation was assessed in pMCI in both hippocampi and in regions showing greater cortical thinning from Y0 to Y2 compared to CTLs. Hyperactivation was found in pMCI individuals in the right supramarginal gyrus. Persons with pMCI also showed hypoactivation in the left hippocampus and left pars opercularis. Both hyper- and hypoactivation were present at Y0 and Y2 and did not change longitudinally. Activation was not associated with time before dementia diagnosis. Smaller volume and thinner cortical thickness were associated with shorter time to diagnosis in the left hippocampus and left pars opercularis. In conclusion, hyperactivation was found in individuals who later progressed to dementia, confirming that it might represent an early biomarker to identify individuals in the prodromal phase of AD and that its understanding could contribute to elucidate the key brain mechanisms that precede dementia.
•Hyperactivation of the right parietal region was found in MCI progressors.•Hypoactivation was found in the hippocampal and frontal regions.•This overall pattern was specific to MCI who progressed to dementia.
Targeting at a factor 20 reduction of the environmental load of buildings in 2040, it is necessary and logical to start by reducing the environmental load of the most important aspects of a building. ...The bearing structure is responsible for the second largest part of the environmental load of the building; the energy consumption is responsible for the greater part, assuming the life span of a building is 75 years (van den Dobbelsteen & van der Linden, 2000)2. The bearing structure consists of the foundation, columns, beams, floor and roof structure, and sometimes walls and facades. The horizontal elements of the bearing structure, comprising of the floor, roof structure and beams, are causing about 80% of the environmental load of the total bearing structure. Particularly the floor & roof structure play a very remarkable role (Arets, 2000). Therefore, optimization of the floor structure will lead to an important environmental improvement of the whole office building. The question which structural material is ecologically or economically best, depends on the span the building design needs. For each floor type, for structural spans between 4.8 and 16.8 m, the environmental load and cost have been determined, resulting in a clear overview of best solutions for different spans.
Background: India is the world's third largest tobacco-growing country. The Indian scenario as far as tobacco consumption is concerned is far worse because of the prevalence of the tobacco chewing ...habit which covers a wide spectrum of socioeconomic and ethnic groups and is spread over urbanized area as well as remote village.Despite the facts, that the harmful effects of tobacco chewing and smoking are widely known, many young people start smoking during adolescence, largely because they believe that smoking will boost their social acceptability and image. This study was contemplated with an aim to assess tobacco / smoking habits and awareness about anti-smoking act among general public in Gurgaon, Haryana, India. Methods: A structured questionnaire consisting of 14 questions related to tobacco/smoking habits and awareness about anti-smoking act were asked to general public and their response was recorded.Random sampling method was used and data was collected from a cross-sectional survey. Results: The study population consisted of total 430 individuals , male 364 (84.65%) and females 66(15.34%) . Then the questionnaires were asked and statistically analyzed. Around 286 (78.57%) from 364 male were indulged in some form of tobacco usage (smoker =32.86% , tobacco chewer = 16.78% , both =11.18 % , alcohol +tobacco user =21.67%). Conclusions: In the present study , most common cause of tobacco use was pleasure 40.5% , inducing factor were friends 53.1% followed by parents and siblings . 36.20% patients used tobacco as second hand exposure in job places. 54.8% were aware about the anti-smoking act in public places, so only 8.6% people from all males enrolled, were smoking in public places.
It is proposed that the prodromal phase of Alzheimer's disease is associated with additional brain activation in key regions involved in memory, reflecting compensatory brain plasticity. Very little ...is known, however, about the evolution of these compensatory mechanisms as the brain acquires more damages. We conducted an fMRI memory study measuring brain activation related to old/new (item recognition) and intact/rearranged (associative recognition) word-pair recognition paradigms in 26 persons with mild cognitive impairment (MCI) and 14 healthy older adults. The Mattis Dementia Rating Scale was used to divide persons with MCI into those with higher and lower cognitive performances. Results indicated more brain activation in MCIs than in controls but disease severity determined which cognitive process was associated with larger activation: Persons with less severe MCI showed hyperactivation during associative recognition only, whereas persons with more severe MCI showed hyperactivation during item recognition only. These hyperactivations were found mainly in brain areas that are typically associated with retrieval mode (e.g., bilateral prefrontal cortex). These findings indicate that neural plasticity occurs during the entire MCI phase but that it is associated with different cognitive components. As they progress in the disease, individuals with MCI will experience a breakdown in the compensatory mechanisms for associative recognition accompanied by emergence of compensatory mechanisms for item recognition.
PDF
