Withdrawal symptoms of electrical brain stimulation in a probabilistic decision making task

Question – It has been shown that transcranial electrical brain stimulation (TES) can improve many aspects of cognition, including decision making and learning. However, it has not been studied whether brain is capable of adapting itself to perform at least equally well without TES, after initially learning the task under influence of TES. We used a probabilistic learning task to investigate this question. Methods – Participants (n = 10) took part in two groups of active (n = 5) and sham (n = 5) transcranial direct current stimulation (tDCS). Each participant attended two experimental sessions. In both sessions participants were asked to perform a probabilistic decision making task. In this task participants adapted to changes in reward contingencies. Participants were presented with two options of which one of them was designated as the better one, leading to higher possibility of rewarding than punishing feedback. Participants were asked to maximise their gain by choosing the better option. The contingencies changed over the course of the trials. Consequently participants had to adjust to the changes in the environment. In the first session, participants in the active and sham tDCS groups, received 15 minutes and 16 seconds of anodal tDCS over their left dorsolateral prefrontal cortex, respectively. For all participants sham stimulation was administered in the second session. Number of rewards in both sessions was recorded and their difference was considered for analysis. Results – Comparison of difference of acquired rewards between the two sessions showed that participants in the active group tend to perform worse than those in the sham group. Conclusions – This result shows that learning under the influence of TES leads to adaptation which induces changes that might not be efficient without TES in a later phase. In more general terms, this result indicates that learning a task under the influence of TES leads to creation of a model which might not be valid anymore without TES

On the Parameterized Complexity of Sparsest Cut and Small-set Expansion Problems

We study the NP-hard \textsc{$k$-Sparsest Cut} problem ($k$SC) in which, given an undirected graph $G = (V, E)$ and a parameter $k$, the objective is to partition vertex set into $k$ subsets whose maximum edge expansion is minimized. Herein, the edge expansion of a subset $S \subseteq V$ is defined as the sum of the weights of edges exiting $S$ divided by the number of vertices in $S$. Another problem that has been investigated is \textsc{$k$-Small-Set Expansion} problem ($k$SSE), which aims to find a subset with minimum edge expansion with a restriction on the size of the subset. We extend previous studies on $k$SC and $k$SSE by inspecting their parameterized complexity. On the positive side, we present two FPT algorithms for both $k$SSE and 2SC problems where in the first algorithm we consider the parameter treewidth of the input graph and uses exponential space, and in the second we consider the parameter vertex cover number of the input graph and uses polynomial space. Moreover, we consider the unweighted version of the $k$SC problem where $k \geq 2$ is fixed and proposed two FPT algorithms with parameters treewidth and vertex cover number of the input graph. We also propose a randomized FPT algorithm for $k$SSE when parameterized by $k$ and the maximum degree of the input graph combined. Its derandomization is done efficiently. \noindent On the negative side, first we prove that for every fixed integer $k,\tau\geq 3$, the problem $k$SC is NP-hard for graphs with vertex cover number at most $\tau$. We also show that $k$SC is W[1]-hard when parameterized by the treewidth of the input graph and the number~$k$ of components combined using a reduction from \textsc{Unary Bin Packing}. Furthermore, we prove that $k$SC remains NP-hard for graphs with maximum degree three and also graphs with degeneracy two. Finally, we prove that the unweighted $k$SSE is W[1]-hard for the parameter $k$

Physical exercise improves long-term memory no less than transcranial direct current stimulation

Question – It has been shown that electrical brain stimulation, in particular transcranial direct current stimulation (tDCS), can improve memory performance. Physical exercise has also been shown to be able to improve different aspects of cognition. The aim of this study was to investigate which of these methods is more effective in improvement of long-term memory. Those tDCS and physical exercise protocols were chosen that have been shown to be effective in improvement of long-term memory: tDCS during memorisation (targeting encoding phase) and physical exercise after memorisation (targeting consolidation phase). We expected to see improvement following application of both methods. No prediction was made on which method is more effective. Methods – Participants (n = 24) took part in three experimental sessions. They were asked to memorise a set of images (‘encoding’) for a later old/new recognition task (‘recognition’). In one of the sessions participants were asked to cycle for 30 minutes on an exercise bike following encoding. In the other two sessions they received either 15 minutes (‘active’ stimulation) or 16 seconds (‘sham’ stimulation) of 1.5 mA anodal tDCS applied over the left dorsolateral prefrontal cortex (left-DLPFC). Performance of the participants in the recognition phase was recorded for analysis. Results – Both physical exercise and active stimulation led to significant improvement of long-term memory performance compared to sham stimulation (paired sample t-test p active tDCS). Conclusions – These results show that only 30 minutes of physical exercise can significantly improve long-term memory performance. Furthermore, this duration of physical exercise during consolidation was more effective than 15 minutes of tDCS during encoding. Considering that tentatively physical exercise lead to less adverse side effects as compared to electrical brain stimulation, physical exercise can be considered potentially a more effective method of cognitive enhancement, in particular in healthy participants

Investigating the role of parietal and prefrontal cortices in spatial working memory using tDCS

Question – Working memory involves the temporary storage, processing, and manipulation of information. Previous studies have suggested that the posterior parietal cortex (PPC), and dorsolateral prefrontal cortex (DLPFC) are involved in spatial working memory, and spatial and object working memory, respectively. The aim of the present pilot study was to investigate whether modulation of the activity of the left PPC and the left DLPFC changes spatial, and object working memory performance. Transcranial direct current stimulation (tDCS) was used for this purpose. Based on past literature we expected to see improvement of both spatial and object working memory after tDCS of the left DLPFC as well as improvement of spatial working memory after tDCS of the left PPC. Methods – Participants (n = 12) attended three experimental sessions with different stimulation conditions. Fifteen minutes of 1.5 mA anodal tDCS was applied over either the left PPC, left DLPFC or occipital lobe as control condition, beginning five minutes before the task. Participants were required to perform a 2-back spatial and object working memory task; i.e., they were required to pay attention to both objects and their location. Abstract objects were presented on either of an eight locations placed on a virtual circle around the centre of the screen. In addition to a 2-back object working memory task, occasionally participants were asked to indicate the location of the object they saw two screens previously. Performance in three different conditions was measured for analysis: (1) 2-back working memory task for the cases in which both cue and target objects were presented in the same location (OWM-same), (2) in different location (OWM-different) and (3) spatial working memory (SWM). Results – Preliminary results showed that performance in the OWM-different condition was lower than OWM-same. There, however, was no significant different between different stimulation conditions. Conclusions – These results suggest that anodal tDCS to the left PPC and left DLPFC might not be able to modulate spatial, and object working memory performance. Further studies are needed to investigate the differential role(s) of the DLPFC and PPC in spatial and working memory

Prevalence of Metabolic Syndrome and Insulin Resistance in Children and Adolescent of Qazvin, Iran

BACKGROUND: The prevalence of metabolic syndrome (MetSyn) is increasing worldwide. The aim of this study was to determine the prevalence of MetSyn and insulin resistance (IR) in children and adolescents in Qazvin, Iran. METHODS: A cross-sectional study was conducted in 338 children and adolescents aged 10–18 years old who were selected by a multistage cluster random sampling method. We performed standardised measurements of variables including waist circumference (WC), blood pressure, plasma glucose level, total cholesterol, high-density lipoprotein cholesterol (HDL), triglycerides, and insulin. MetSyn was defined according to the International Diabetes Federation criteria. IR was estimated by the homeostatic model assessment. RESULTS: Of the 338 total subjects, 172 were female. The overall prevalence of MetSyn and IR were 3.4% and 18.2%, respectively. There was no sex difference for the prevalence of MetSyn. A total of 185 subjects (56.4%) had one or two components of MetSyn. The most common component was low HDL levels in both sexes, which was followed by high WC in females and high fasting plasma glucose levels in males. CONCLUSION: The lack of a standard definition of MetSyn in children and adolescents combined with the geographical and socioeconomic differences make it difficult to compare the results from different studies. Modification of lifestyle habits is an important strategy in preventing MetSyn and IR

On nodal domains of finite reversible Markov processes and spectral decomposition of cycles

24 pagesInternational audienceLet $L$ be a reversible Markovian generator on a finite set $V$. Relations between the spectral decomposition of $L$ and subpartitions of the state space $V$ into a given number of components which are optimal with respect to min-max or max-min Dirichlet connectivity criteria are investigated. Links are made with higher order Cheeger inequalities and with a generical characterization of subpartitions given by the nodal domains of an eigenfunction. These considerations are applied to generators whose positive rates are supported by the edges of a discrete cycle $\mathbf{Z}_N$, to obtain a full description of their spectra and of the shapes of their eigenfunctions, as well as an interpretation of the spectrum through a double covering construction. Also, we prove that for these generators, higher Cheeger inequalities hold, with a universal constant factor 48

Correlation between food habits and time spent watching television with sleep quality at children and teenagers, MINOODAR Qazvin

Introduction: Children from the age of each person's life so that people's eating habits are formed during this period. Some studies of the relationship between TV viewing time and also how sleep quality and eating habits in children and adolescents are supported, but others do not approve of the presence of such a relationship. This study aimed to investigate the association between dietary habits and TV viewing time sleep quality in children and adolescents 10-18 years Minoodar Qazvin. Materials and methods: The study population of 10-18 year old population research center was MINOODAR. Sampling using multi-stage cluster random sampling was performed. All demographic, anthropometric and nutrition, as well as questions related to sleep quality standard questionnaire and was collected by trained personnel. Data were analyzed using spss softwareversion16. Findings: Most of the adolescents studied food groups: grains, meat and oil more than the recommended but milk and dairy product and vegetable group were receiving less than the recommended amount. The results showed that boys compared with girls, bread and cereals (p=0/005) and milk and milk products (p=0/048) received more. Also, people who had low sleep quality was higher consumption of bread and cereals (p= 0/01). People with normal sleep omega-3 fatty acids consumed more (p<0/05). The regression analysis of sleep quality with age, gender, time of watching TV, playing video games and get the time of caffeine was no observed. Conclusions: The nutritional status of adolescents in need of reform. This study showed that eating less bread and refined grains and omega-3 fatty acid intake may increase sleep quality in children and adolescents are more boys than girls drank milk and dairy products, so the problem of delay sleep and irregular sleep was less. Also watching TV for 2 hours a day will have no effect on quality of sleep, however, to verify the results of this study, further research is needed in this area

Investigating Cause and Effect Relationships and Prioritizing of GM Assessment Indexes based on Economic, Resources, Energy and Environmental Attributes and PSR Framework using Gray DEMATAL

Nowadays the role of green manufacturing (GM) in sustainable development is evident and irrefutable therefore organizations seek to introduce themselves green in order to maintain their image toward their community. The usual method of sustainability and greenness assessment of a system is making use of indicators and indexes which are classified into several groups based on their characteristics. An important type of index categorization is based on four sustainability attributes including economic, energy, environment and recourses as well as pressure-state-response model (PSR). Because of the research gap about interactions relationships on indexes and investigating their influence others and influence by others. Since, indexes in each group could be effective on other indexes and be overlapped to some extent, it is necessary to prioritize and evaluate cause and effect relations by use of an appropriate method. We consider the relationship and prioritize most important indexes to evaluate manufacturing' greenness based on aforementioned sustainability attributes and PSR model. Purpose data is gathered by survey GM experts questionnaires, including 41 indexes plus 4 mentioned attributes, totally as 45 factors in 13 groups. In order to data analysis, with respect to the non-certainty and insufficient information, Grey DEMATEL method is used.Atualmente, o papel da manufatura verde (GM, Green Manufacturing) no desenvolvimento sustentável é evidente e irrefutável, portanto, as organizações procuram se apresentar “verdes” para manter sua imagem em sua comunidade. O método usual de avaliação da sustentabilidade e do verdor de um sistema é o uso de indicadores e índices que são classificados em vários grupos com base em suas características. Um tipo importante de categorização de índices é baseado em quatro atributos de sustentabilidade, incluindo econômico, energia, meio ambiente e recursos, além do modelo pressão-resposta-estado (PSR, Pressure-State-Response). Tendo em vista a lacuna de pesquisa sobre as relações de interações em índices faz-se necessário investigar a influência de outros e quais são influenciados por outros. Como os índices em cada grupo podem ser efetivos em outros índices e serem sobrepostos em certa medida, assim é essencial priorizar e avaliar as relações de causa e efeito pelo uso de um método apropriado. Consideramos o relacionamento e priorizamos os índices mais importantes para avaliar o verdor da manufatura com base nos atributos de sustentabilidade e no modelo de PSR. Os dados são coletados por questionários especializados em GM, incluindo 41 índices mais os 4 atributos mencionados, totalizando 45 fatores em 13 grupos. A fim de analisar os dados, no que diz respeito às informações não seguras e insuficientes, é utilizado o método Gray DEMATEL