Stimulus Simplification and Object Representation: A Modeling Study

Tsunoda et al. (2001) recently studied the nature of object representation in monkey inferotemporal cortex using a combination of optical imaging and extracellular recordings. In particular, they examined IT neuron responses to complex natural objects and "simplified" versions thereof. In that study, in 42% of the cases, optical imaging revealed a decrease in the number of activation patches in IT as stimuli were "simplified". However, in 58% of the cases, "simplification" of the stimuli actually led to the appearance of additional activation patches in IT. Based on these results, the authors propose a scheme in which an object is represented by combinations of active and inactive columns coding for individual features. We examine the patterns of activation caused by the same stimuli as used by Tsunoda et al. in our model of object recognition in cortex (Riesenhuber 99). We find that object-tuned units can show a pattern of appearance and disappearance of features identical to the experiment. Thus, the data of Tsunoda et al. appear to be in quantitative agreement with a simple object-based representation in which an object's identity is coded by its similarities to reference objects. Moreover, the agreement of simulations and experiment suggests that the simplification procedure used by Tsunoda (2001) is not necessarily an accurate method to determine neuronal tuning.

Categorization in IT and PFC: Model and Experiments

In a recent experiment, Freedman et al. recorded from inferotemporal (IT) and prefrontal cortices (PFC) of monkeys performing a "cat/dog" categorization task (Freedman 2001 and Freedman, Riesenhuber, Poggio, Miller 2001). In this paper we analyze the tuning properties of view-tuned units in our HMAX model of object recognition in cortex (Riesenhuber 1999) using the same paradigm and stimuli as in the experiment. We then compare the simulation results to the monkey inferotemporal neuron population data. We find that view-tuned model IT units that were trained without any explicit category information can show category-related tuning as observed in the experiment. This suggests that the tuning properties of experimental IT neurons might primarily be shaped by bottom-up stimulus-space statistics, with little influence of top-down task-specific information. The population of experimental PFC neurons, on the other hand, shows tuning properties that cannot be explained just by stimulus tuning. These analyses are compatible with a model of object recognition in cortex (Riesenhuber 2000) in which a population of shape-tuned neurons provides a general basis for neurons tuned to different recognition tasks.

Análisis de la incidencia de la Teoría de la Identidad Colectiva en la posición de la Liga Árabe frente al reconocimiento de Somalilandia como Estado independiente

Esta Monografía se centra en mostrar cómo el intento por conservar la identidad colectiva de la Liga de los Estados Árabes impide ceder ante el deseo de Somalilandia de ser reconocida como Estado independiente.

El desarrollo de la escuela media comprensiva en Suecia : investigación y evaluación.

En Suecia, existen dos concepciones tradicionales de la escuela, y para comprenderse se describen y explican la evolución de la escuela media y su evaluación. Se entiende por escuela media los cursos 7 a 9 de la escuela comprensiva (de 13 a 16 años). Se hace un repaso por la historia de la educación en Suecia, con el fin de entender las reformas que experimenta su sistema educativo. Se considera un sistema de escuela tradicional remodelado por nuevas motivaciones y situado en otro contexto económico, social y cultural.

La dirección por objetivos y la evaluación en la educación noruega.

Se desarrollan dos modelos teóricos para poder distinguir entre las distintas finalidades que deben cumplir la dirección y la evaluación educativas dentro del sistema educativo noruego. La dirección por objetivos se describe como una dirección que se sirve de los objetivos y la evaluación, donde la educación está más abierta a la sociedad, lo que da lugar a un cambio en la orientación educativa. El modelo se basa en la dirección nacional y garantiza que los derechos y los objetivos fundamentales no se subordinan a intereses específicos. Se desarrolla el proyecto EMIL, cuyo objetivo es analizar qué evaluación de la educación abarca los problemas concretos que afronta el sistema educativo noruego, y en relación con la competencia que existe en noruega en el ámbito de la evaluación educativa.

Nuevos desafíos para los profesores y para la formación del profesorado : informe presentado a la Conferencia Permanente de Ministros Europeos de Educación del Consejo de Europa (15ª Sesión, Helsinki, 5-7 de mayo de 1987).

Existen numerosos problemas en la educación que son permanentes como la selección de los contenidos de la enseñanza y la relación de estos con el mundo exterior que han sido afrontados de diferentes formas en distintos momentos de la historia. La lista de los desafíos planteados a los profesores y a la formación del profesorado no es infinita, pero si larga. La cuestión no es identificar fenómenos aislados que sean un desafío sino determinar los problemas que afronta la educación derivados de los cambios a los que esta puede responder. Uno de los más influyentes es el de los profesores y su formación: en este sentido la profesión docente no se ha desarrollado hacia una mayor profesionalización sino hacia la desprofesionalización. Parte importante de este proceso es el hecho de que las decisiones acerca de los objetivos, métodos y contenidos de enseñanza han dejado de ser , al menos en parte, competencia de los profesores. Así, la administración de la educación y la capacidad política para gestionar la actividad educativa tiene una importancia decisiva para que los docentes puedan desempeñar su trabajo. Esta desprofesionalización ha supuesto una pérdida de status y prestigio reflejada tanto en el reclutamiento de los nuevos docentes como en la situación de la formación del profesorado no avalada por la universidad y por las múltiples reformas educativas. Por lo que se plantea una educación para todos y una nueva pedagogía que incida en la formación profesional del profesor en el sentido de darle un bagaje completo que le permita ocupar un papel adecuado en la enseñanza al tener claro que es lo que debe enseñar y para que sirve.; Otro gran problema a resolver es la sobrecarga curricular. Lo que implica que los profesores encuentran dificultades para poner en práctica un programa y seleccionar lo que es esencial. El resultado es que los contenidos de aprendizaje se presentan de forma superficial. Una posible solución a este problema es dar más competencia a los profesores; Uno de los desafíos más difíciles que tiene planteada la educación es la aplicación de las nuevas tecnologías no sólo el ordenador, sino todos los medios existentes en la sociedad actual. Las nuevas tecnologías repercuten en la forma en que aprenden los alumnos e incluso en sus expectativas de aprendizaje. Además, no son sólo un medio de enseñanza, sino también una materia que enseñar. El uso de ellas, no puede ser un fin, sólo un medio. Su aplicación no tendrá ningún futuro a menos que se lleve a cabo con el respeto debido a los objetivos de enseñanza establecidos por la escuela y con una finalidad exclusivamente educativa, y a menos que los profesores que deban utilizarlas gocen de unas condiciones de formación, óptimas así como de las mejores condiciones materiales posibles para dicha aplicación; Otro tema es el libro de texto que con las utilización de ordenadores para su confección por parte del profesor mejoraría la calidad de la enseñanza; Y como último tema el contexto moral: la profesión docente tiene que relacionarse con los fines más complejos y sutiles de la educación contemporánea, a saber, formar la personalidad y educar a ciudadanos responsables. Tarea que ofrece especiales dificultades en una sociedad pluricultural. Estas dificultades aumentan todavía más en una situación en la que muchos jóvenes que salen de las escuelas no encuentran un empleo estable, cuando pensaban que la educación sería un medio de acceder al mercado de trabajo. Este problema moral en la educación no puede considerarse algo que puede enseñarse como cualquier asignatura, Es algo que hay que abordar en los procesos educativos diarios , a través del modo en que los profesores trabajan y tratan a sus alumnos.

PISA como instrumento pol??tico : la historia detr??s de la creaci??n del programa PISA

Resumen tomado de la publicaci??n

ACC2 gene polymorphisms, metabolic syndrome, and gene-nutrient interactions with dietary fat.

Acetyl-CoA carboxylase β (ACC2) plays a key role in fatty acid synthesis and oxidation pathways. Disturbance of these pathways is associated with impaired insulin responsiveness and metabolic syndrome (MetS). Gene-nutrient interactions may affect MetS risk. This study determined the relationship between ACC2 polymorphisms (rs2075263, rs2268387, rs2284685, rs2284689, rs2300453, rs3742023, rs3742026, rs4766587, and rs6606697) and MetS risk, and whether dietary fatty acids modulate this in the LIPGENE-SU.VI.MAX study of MetS cases and matched controls (n = 1754). Minor A allele carriers of rs4766587 had increased MetS risk (OR 1.29 [CI 1.08, 1.58], P = 0.0064) compared with the GG homozygotes, which may in part be explained by their increased body mass index (BMI), abdominal obesity, and impaired insulin sensitivity (P < 0.05). MetS risk was modulated by dietary fat intake (P = 0.04 for gene-nutrient interaction), where risk conferred by the A allele was exacerbated among individuals with a high-fat intake (>35% energy) (OR 1.62 [CI 1.05, 2.50], P = 0.027), particularly a high intake (>5.5% energy) of n-6 polyunsaturated fat (PUFA) (OR 1.82 [CI 1.14, 2.94], P = 0.01; P = 0.05 for gene-nutrient interaction). Saturated and monounsaturated fat intake did not modulate MetS risk. Importantly, we replicated some of these findings in an independent cohort. In conclusion, the ACC2 rs4766587 polymorphism influences MetS risk, which was modulated by dietary fat, suggesting novel gene-nutrient interactions.

Effects of dietary fat modification on oxidative stress and inflammatory markers in the LIPGENE study.

Subjects with the metabolic syndrome (MetS) have enhanced oxidative stress and inflammation. Dietary fat quality has been proposed to be implicated in these conditions. We investigated the impact of four diets distinct in fat quantity and quality on 8-iso-PGF2α (a major F2-isoprostane and oxidative stress indicator), 15-keto-13,14-dihydro-PGF2α (15-keto-dihydro-PGF2α, a major PGF2α metabolite and marker of cyclooxygenase-mediated inflammation) and C-reactive protein (CRP). In a 12-week parallel multicentre dietary intervention study (LIPGENE), 417 volunteers with the MetS were randomly assigned to one of the four diets: two high-fat diets (38 % energy (%E)) rich in SFA or MUFA and two low-fat high-complex carbohydrate diets (28 %E) with (LFHCC n-3) or without (LFHCC) 1·24 g/d of very long chain n-3 fatty acid supplementation. Urinary levels of 8-iso-PGF2α and 15-keto-dihydro-PGF2α were determined by RIA and adjusted for urinary creatinine levels. Serum concentration of CRP was measured by ELISA. Neither concentrations of 8-iso-PGF2α and 15-keto-dihydro-PGF2α nor those of CRP differed between diet groups at baseline (P>0·07) or at the end of the study (P>0·44). Also, no differences in changes of the markers were observed between the diet groups (8-iso-PGF2α, P = 0·83; 15-keto-dihydro-PGF2α, P = 0·45; and CRP, P = 0·97). In conclusion, a 12-week dietary fat modification did not affect the investigated markers of oxidative stress and inflammation among subjects with the MetS in the LIPGENE study.

Dietary fat modifications and blood pressure in subjects with the metabolic syndrome in the LIPGENE dietary intervention study

Hypertension is a key feature of the metabolic syndrome. Lifestyle and dietary changes may affect blood pressure (BP), but the knowledge of the effects of dietary fat modification in subjects with the metabolic syndrome is limited. The objective of the present study was to investigate the effect of an isoenergetic change in the quantity and quality of dietary fat on BP in subjects with the metabolic syndrome. In a 12-week European multi-centre, parallel, randomised controlled dietary intervention trial (LIPGENE), 486 subjects were assigned to one of the four diets distinct in fat quantity and quality: two high-fat diets rich in saturated fat or monounsaturated fat and two low-fat, high-complex carbohydrate diets with or without 1·2 g/d of very long-chain n-3 PUFA supplementation. There were no overall differences in systolic BP (SBP), diastolic BP or pulse pressure (PP) between the dietary groups after the intervention. The high-fat diet rich in saturated fat had minor unfavourable effects on SBP and PP in males.

Serum vitamin D concentration does not predict insulin action or secretion in European subjects with the metabolic syndrome

OBJECTIVE To investigate the relation between serum concentration of 25-hydroxyvitamin D [25(OH)D] and insulin action and secretion. RESEARCH DESIGN AND METHODS In a cross-sectional study of 446 Pan-European subjects with the metabolic syndrome, insulin action and secretion were assessed by homeostasis model assessment (HOMA) indexes and intravenous glucose tolerance test to calculate acute insulin response, insulin sensitivity, and disposition index. Serum 25(OH)D was measured by high-performance liquid chromatography/mass spectrometry. RESULTS The 25(OH)D3 concentration was 57.1 ± 26.0 nmol/l (mean ± SD), and only 20% of the subjects had 25(OH)D3 levels ≥75 nmol/l. In multiple linear analyses, 25(OH)D3 concentrations were not associated with parameters of insulin action or secretion after adjustment for BMI and other covariates. CONCLUSIONS In a large sample of subjects with the metabolic syndrome, serum concentrations of 25(OH)D3 did not predict insulin action or secretion. Clear evidence that D vitamin status directly influences insulin secretion or action is still lacking.

NOS3 gene polymorphisms are associated with risk markers of cardiovascular disease, and interact with omega-3 polyunsaturated fatty acids

Objective Omega-3 polyunsaturated fatty acids (n-3 PUFA) may protect against the development of cardiovascular disease (CVD). Genotype at key genes such as nitric oxide synthase (NOS3) may determine responsiveness to fatty acids. Gene–nutrient interactions may be important in modulating the development of CVD, particularly in high-risk individuals with the metabolic syndrome (MetS). Methods Biomarkers of CVD risk, plasma fatty acid composition, and NOS3 single nucleotide polymorphism (SNP) genotype (rs11771443, rs1800783, rs1800779, rs1799983, rs3918227, and rs743507) were determined in 450 individuals with the MetS from the LIPGENE dietary intervention cohort. The effect of dietary fat modification for 12 weeks on metabolic indices of the MetS was determined to understand potential NOS3 gene–nutrient interactions. Results Several markers of inflammation and dyslipidaemia were significantly different between the genotype groups. A significant gene–nutrient interaction was observed between the NOS3 rs1799983 SNP and plasma n-3 PUFA status on plasma triacylglycerol (TAG) concentrations. Minor allele carriers (AC + AA) showed an inverse association with significantly higher plasma TAG concentrations in those with low plasma n-3 PUFA status and vice versa but the major allele homozygotes (CC) did not. Following n-3 PUFA supplementation, plasma TAG concentrations of minor allele carriers of rs1799983 were considerably more responsive to changes in plasma n-3 PUFA, than major allele homozygotes. Conclusions Carriers of the minor allele at rs1799983 in NOS3 have plasma TAG concentrations which are more responsive to n-3 PUFA. This suggests that these individuals might show greater beneficial effects of n-3 PUFA consumption to reduce plasma TAG concentrations.

Structure of single-wall peptide nanotubes: in situ flow aligning X-ray diffraction

The structure of single wall peptide nanotubes is presented for the model surfactant-like peptide A6K. Capillary flow alignment of a sample in the nematic phase at high concentration in water leads to oriented X-ray diffraction patterns. Analysis of these, accompanied by molecular dynamics simulations, suggests the favourable self-assembly of antiparallel peptide dimers into beta-sheet ribbons that wrap helically to form the nanotube wall.