Energy demands of diverse spiking cells from the neocortex, hippocampus, and thalamus

It has long been known that neurons in the brain are not physiologically homogeneous. In response to current stimulus, they can fire several distinct patterns of action potentials that are associated with different physiological classes ranging from regular-spiking cells, fast-spiking cells, intrinsically bursting cells, and low-threshold cells. In this work we show that the high degree of variability in firing characteristics of action potentials among these cells is accompanied with a significant variability in the energy demands required to restore the concentration gradients after an action potential. The values of the metabolic energy were calculated for a wide range of cell temperatures and stimulus intensities following two different approaches. The first one is based on the amount of Na+ load crossing the membrane during a single action potential, while the second one focuses on the electrochemical energy functions deduced from the dynamics of the computational neuron models. The results show that the thalamocortical relay neuron is the most energy-efficient cell consuming between 7 and 18 nJ/cm(2) for each spike generated, while both the regular and fast spiking cells from somatosensory cortex and the intrinsically-bursting cell from a cat visual cortex are the least energy-efficient, and can consume up to 100 nJ/cm(2) per spike. The lowest values of these energy demands were achieved at higher temperatures and high external stimuli.

O discurso da educação de qualidade nas políticas de currículo

Esta pesquisa analisa o discurso de educação de qualidade nas políticas curriculares para a Educação Básica forjadas no Brasil, no período compreendido entre 2003 e 2011, na vigência do governo de Luís Inácio Lula da Silva e no início do governo Dilma Roussef, procurando entender os nexos estabelecidos entre currículo e qualidade. Para tanto, é investigado o contexto de produção dos textos da referida política o Ministério da Educação (MEC), por meio da leitura de cinquenta e sete documentos assinados e/ou encomendados pela Secretaria de Educação Básica (SEB), pelo Conselho Nacional de Educação (CNE) e pelo Instituto Nacional de Estudos e Pesquisas Educacionais (INEP), os quais constituíram um corpus de estudo para esta pesquisa. Tal leitura tem como ferramenta de entrada e organização dos textos o programa computacional WordSmith Tools (versão 5), a partir do qual foi possível focar em significantes identificados como condutores dos sentidos de qualidade. A análise desse corpus de estudo é relacionada ainda aos programas de governo divulgados pelo Partido dos Trabalhadores na ocasião das campanhas eleitorais de 2002, 2006 e 2010, com vistas a uma maior compreensão do contexto político partidário ao qual a política curricular se conecta. A pesquisa se fundamenta na Teoria do Discurso de Ernesto Laclau, articulada às teorias do currículo produzidas por Alice Lopes e Elizabeth Macedo e à abordagem do ciclo de políticas de Stephen Ball e colaboradores. Com essa filiação teórica entende-se as políticas de currículo como produção cultural discursiva em múltiplos contextos, marcada pela contingência do social. A tese apresentada é a de que, na política Lula/Dilma, o significante educação de qualidade é tendencialmente vazio, representando, no que se refere ao currículo, tanto demandas por um ensino voltado para a distribuição igualitária do conhecimento, visto como possibilidade de promover a justiça social, quanto demandas por um ensino voltado para resultados estipulados e mensurados por meio de sistemas de avaliação nacional que atestam sua eficiência e que representam o discurso da qualidade que se pretende total, segundo o qual a educação é um investimento que precisa dar retornos. A equivalência entre demandas, aparentemente, antagônicas, é possibilitada pelo vínculo que o significante qualidade estabelece com a demanda por justiça social, ao ser adjetivado como social, dando origem ao discurso da qualidade social. A política de qualidade social da educação, portanto, constrói um discurso de promoção da justiça social por meio do currículo comum e da centralidade do conhecimento (verificável), lançando mão do vocabulário das perspectivas críticas e ao mesmo tempo utilizando-se de ações das perspectivas instrumentais, que reduz o currículo às dimensões instrucionais. São, portanto, duas cadeias de equivalência em disputa no cenário educacional: a cadeia da qualidade social, representada pelo projeto de poder Lula/Dilma, que se justifica pela demanda da justiça social e opera a ressignificação das lógicas da centralização curricular e suas formas de avaliar, e a cadeia da qualidade que se pretende total, representada pelo projeto de poder FHC, que condiciona a educação às demandas de produtividade do mercado

Number of Players and Relative Pitch Area per Player: Comparing Their Influence on Heart Rate and Physical Demands in Under-12 and Under-13 Football Players

The aim of the present study is to analyse the influence of different large-sided games (LSGs) on the physical and physiological variables in under-12s (U12) and -13s (U13) soccer players. The effects of the combination of different number of players per team, 7, 9, and 11 (P7, P9, and P11, respectively) with three relative pitch areas, 100, 200, and 300 m(2) (A100, A200, and A300, respectively), were analysed in this study. The variables analysed were: 1) global indicator such as total distance (TD); work:rest ratio (W:R); player-load (PL) and maximal speed (V-max); 2) heart rate (HR) mean and time spent in different intensity zones of HR (<75%, 75-84%, 84-90% and >90%), and; 3) five absolute (<8, 8-13, 13-16 and >16 Km h(-1)) and three relative speed categories (<40%, 40-60% and >60% V-max). The results support the theory that a change in format (player number and pitch dimensions) affects no similarly in the two players categories. Although it can seem that U13 players are more demanded in this kind of LSG, when the work load is assessed from a relative point of view, great pitch dimensions and/or high number of player per team are involved in the training task to the U12 players. The results of this study could alert to the coaches to avoid some types of LSGs for the U12 players such as:P11 played in A100, A200 or A300, P9 played in A200 or A300 and P7 played in A300 due to that U13>U12 in several physical and physiological variables (W:R, time spent in 84-90% HRmax, distance in 8-13 and 13-16 Km h(-1) and time spent in 40-60% V-max). These results may help youth soccer coaches to plan the progressive introduction of LSGs so that task demands are adapted to the physiological and physical development of participants.

Investigating the relationships between user capabilities and product demands for older and disabled users

This paper presents the results of a study that specifically looks at the relationships between measured user capabilities and product demands in a sample of older and disabled users. An empirical study was conducted with 19 users performing tasks with four consumer products (a clock-radio, a mobile phone, a blender and a vacuum cleaner). The sensory, cognitive and motor capabilities of each user were measured using objective capability tests. The study yielded a rich dataset comprising capability measures, product demands, outcome measures (task times and errors), and subjective ratings of difficulty. Scatter plots were produced showing quantified product demands on user capabilities, together with subjective ratings of difficulty. The results are analysed in terms of the strength of correlations observed taking into account the limitations of the study sample. Directions for future research are also outlined. © 2011 Springer-Verlag.

User responses to the learning demands of consumer products

Designers are typically male, under 35 years old and unimpaired. Users can be of any age and currently over 15% will have some form of impairment. As a result a vast array of consumer products suit youthful males and in many cases exclude other demographics (e.g. Keates and Clarkson, 2004). In studying the way a range of users learn how to use new products, key cognitive difficulties are revealed and linked back to the areas of the product causing the problems. The trials were structured so each user had to complete a specific set of tasks and were consistent across the user spectrum. The tasks set aimed to represent both everyday usage and less familiar functions. Whilst the knowledge gained could provide designers with valuable guidelines for the specific products examined, a more general abstraction provides knowledge of the pitfalls to avoid in the design of other product families.

The temporal evolution of feedback gains rapidly update to task demands.

Recent theoretical frameworks such as optimal feedback control suggest that feedback gains should modulate throughout a movement and be tuned to task demands. Here we measured the visuomotor feedback gain throughout the course of movements made to "near" or "far" targets in human subjects. The visuomotor gain showed a systematic modulation over the time course of the reach, with the gain peaking at the middle of the movement and dropping rapidly as the target is approached. This modulation depends primarily on the proportion of the movement remaining, rather than hand position, suggesting that the modulation is sensitive to task demands. Model-predictive control suggests that the gains should be continuously recomputed throughout a movement. To test this, we investigated whether feedback gains update when the task goal is altered during a movement, that is when the target of the reach jumped. We measured the visuomotor gain either simultaneously with the jump or 100 ms after the jump. The visuomotor gain nonspecifically reduced for all target jumps when measured synchronously with the jump. However, the visuomotor gain 100 ms later showed an appropriate modulation for the revised task goal by increasing for jumps that increased the distance to the target and reducing for jumps that decreased the distance. We conclude that visuomotor feedback gain shows a temporal evolution related to task demands and that this evolution can be flexibly recomputed within 100 ms to accommodate online modifications to task goals.

Robert Heinich, Michael Molenda, James D. Russell, Sharon E. Smaldino, Instructional Media and Technologies for Learning, Prentice-Hall, Inc., Englewood Cliffs, New Jersey 1996, ss. 446. Steven Hackbarth, The Educational Technology Handbook. A Comprehensive Guide, Educational Technology Publications Inc., Englewood Cliffs, New Jersey 1996, ss. 351

Recenzje i sprawozdania z książek

On the Convergence of Statistical Techniques for Inferring Network Traffic Demands

Accurate knowledge of traffic demands in a communication network enables or enhances a variety of traffic engineering and network management tasks of paramount importance for operational networks. Directly measuring a complete set of these demands is prohibitively expensive because of the huge amounts of data that must be collected and the performance impact that such measurements would impose on the regular behavior of the network. As a consequence, we must rely on statistical techniques to produce estimates of actual traffic demands from partial information. The performance of such techniques is however limited due to their reliance on limited information and the high amount of computations they incur, which limits their convergence behavior. In this paper we study strategies to improve the convergence of a powerful statistical technique based on an Expectation-Maximization iterative algorithm. First we analyze modeling approaches to generating starting points. We call these starting points informed priors since they are obtained using actual network information such as packet traces and SNMP link counts. Second we provide a very fast variant of the EM algorithm which extends its computation range, increasing its accuracy and decreasing its dependence on the quality of the starting point. Finally, we study the convergence characteristics of our EM algorithm and compare it against a recently proposed Weighted Least Squares approach.

A Two-step Statistical Approach for Inferring Network Traffic Demands (Revises Technical Report BUCS-2003-003)

Accurate knowledge of traffic demands in a communication network enables or enhances a variety of traffic engineering and network management tasks of paramount importance for operational networks. Directly measuring a complete set of these demands is prohibitively expensive because of the huge amounts of data that must be collected and the performance impact that such measurements would impose on the regular behavior of the network. As a consequence, we must rely on statistical techniques to produce estimates of actual traffic demands from partial information. The performance of such techniques is however limited due to their reliance on limited information and the high amount of computations they incur, which limits their convergence behavior. In this paper we study a two-step approach for inferring network traffic demands. First we elaborate and evaluate a modeling approach for generating good starting points to be fed to iterative statistical inference techniques. We call these starting points informed priors since they are obtained using actual network information such as packet traces and SNMP link counts. Second we provide a very fast variant of the EM algorithm which extends its computation range, increasing its accuracy and decreasing its dependence on the quality of the starting point. Finally, we evaluate and compare alternative mechanisms for generating starting points and the convergence characteristics of our EM algorithm against a recently proposed Weighted Least Squares approach.

The neural dynamics of stimulus and response conflict processing as a function of response complexity and task demands.

Both stimulus and response conflict can disrupt behavior by slowing response times and decreasing accuracy. Although several neural activations have been associated with conflict processing, it is unclear how specific any of these are to the type of stimulus conflict or the amount of response conflict. Here, we recorded electrical brain activity, while manipulating the type of stimulus conflict in the task (spatial [Flanker] versus semantic [Stroop]) and the amount of response conflict (two versus four response choices). Behaviorally, responses were slower to incongruent versus congruent stimuli across all task and response types, along with overall slowing for higher response-mapping complexity. The earliest incongruency-related neural effect was a short-duration frontally-distributed negativity at ~200 ms that was only present in the Flanker spatial-conflict task. At longer latencies, the classic fronto-central incongruency-related negativity 'N(inc)' was observed for all conditions, but was larger and ~100 ms longer in duration with more response options. Further, the onset of the motor-related lateralized readiness potential (LRP) was earlier for the two vs. four response sets, indicating that smaller response sets enabled faster motor-response preparation. The late positive complex (LPC) was present in all conditions except the two-response Stroop task, suggesting this late conflict-related activity is not specifically related to task type or response-mapping complexity. Importantly, across tasks and conditions, the LRP onset at or before the conflict-related N(inc), indicating that motor preparation is a rapid, automatic process that interacts with the conflict-detection processes after it has begun. Together, these data highlight how different conflict-related processes operate in parallel and depend on both the cognitive demands of the task and the number of response options.

Elementary Principals' Perceptions of a Leadership Development Training Program

Research indicates that school leaders are crucial to improving instruction and raising student achievement (Council of Chief State School Officers, 2008). As such, educational reforms such as the No Child Left Behind Act (2001) and Race to the Top (2009) have sparked an accountability movement where principals are being held accountable for students' academic achievement and educational outcomes. The shift towards greater accountability has placed new attention on the ways principals are trained. Researchers have noted that organized professional development programs have not adequately prepared school principals to meet the priority demands of the 21st century (Hale & Moorman, 2003; Murphy, 1994). Murphy (1994) stated, "Traditional preparation programs - usually pre-service programs based in colleges or universities, that awarded certification and advanced degrees - rarely concentrated on the leadership challenges that principals actually face in real schools" (p. 4). As a result, many school districts are seeking ways to develop leadership development training programs that will prepare principals for their job responsibilities as a school leader. In spite of the additional training principals receive, researchers suggests that there is an obvious gap between the readiness of administrators to be instructional leaders and the demands for accountability that school administrators face (Hale & Moorman, 2003). This quantitative study examined elementary school principals' perceptions of their leadership development training program. Guided by four research questions, the study examined principals' perceptions of their overall training and how well their training prepared them to deal with school and classroom practices that contribute to student achievement; to work with teachers and others to design and implement a system for continuous student achievement; and to provide necessary support to carry out sound school, curriculum, and instructional practices. Data for this study was collected by way of survey responses from a total of 46 elementary school principals. The results from the study revealed that more than half (58.7%) of participants perceived their training as excellent. While principals' perceived that their training adequately prepared them to work collaboratively in teams, set clear visions and goals, and to use data to improve students achievement, many respondents reported a lack of training in being informed and focused on student achievement. Principals also suggested that they were not effectively trained in finding effective ways to obtain support from central office or community members.

Training teachers for further and technical education 1950-1982: staff perceptions of changing demands and policies

This paper aims to create a picture of aspects of the working lives of some trainers of technical and further education teachers in a specialist teacher training college in Bolton, Lancashire, from the 1950s to the 1980's. There is little reference to technical teacher training in the literature on teacher training in the second half of the twentieth century. With this gap in mind, this paper sets out to record some memories and impressions of staff involved during these years. Using data from a series of semi-structured interviews, the discussion centres upon their perceptions of their work: of their students, the working environment, the curriculum and their relationships with the technical colleges for whom they were training teachers. The paper has three sections. It begins with a brief discussion of the issues arising from the choice of research methods. The second section contextualises the study and traces the history of Bolton Technical Teachers' Training College from its establishment through to its merger with the Institute of Technology in 1982. This is followed by the presentation and discussion of the interview data.