Sensory perception relies on fitness-maximizing codes

Sensory information encoded by humans and other organisms is generally presumed to be as accurate as their biological limitations allow. However, perhaps counterintuitively, accurate sensory representations may not necessarily maximize the organism’s chances of survival. To test this hypothesis, we developed a unified normative framework for fitness-maximizing encoding by combining theoretical insights from neuroscience, computer science, and economics. Behavioural experiments in humans revealed that sensory encoding strategies are flexibly adapted to promote fitness maximization, a result confirmed by deep neural networks with information capacity constraints trained to solve the same task as humans. Moreover, human functional MRI data revealed that novel behavioural goals that rely on object perception induce efficient stimulus representations in early sensory structures. These results suggest that fitness-maximizing rules imposed by the environment are applied at early stages of sensory processing in humans and machines

Studying and modifying brain function with non-invasive brain stimulation

In the past three decades, our understanding of brain–behavior relationships has been significantly shaped by research using non-invasive brain stimulation (NIBS) techniques. These methods allow non-invasive and safe modulation of neural processes in the healthy brain, enabling researchers to directly study how experimentally altered neural activity causally affects behavior. This unique property of NIBS methods has, on the one hand, led to groundbreaking findings on the brain basis of various aspects of behavior and has raised interest in possible clinical and practical applications of these methods. On the other hand, it has also triggered increasingly critical debates about the properties and possible limitations of these methods. In this review, we discuss these issues, clarify the challenges associated with the use of currently available NIBS techniques for basic research and practical applications, and provide recommendations for studies using NIBS techniques to establish brain–behavior relationships

Evaluation of high-resolution microarray platforms for genomic profiling of bone tumours

<p>Abstract</p> <p>Background</p> <p>Several high-density oligonucleotide microarray platforms are available for genome-wide single nucleotide polymorphism (SNP) detection and microarray-based comparative genomic hybridisation (array CGH), which may be used to detect copy number aberrations in human tumours. As part of the EuroBoNeT network of excellence for research on bone tumours (eurobonet.eu), we have evaluated four different commercial high-resolution microarray platforms in order to identify the most appropriate technology for mapping DNA copy number aberrations in such tumours.</p> <p>Findings</p> <p>DNA from two different cytogenetically well-characterized bone sarcoma cell lines, representing a simple and a complex karyotype, respectively, was tested in duplicate on four high-resolution microarray platforms; Affymetrix Genome-Wide Human SNP Array 6.0, Agilent Human Genome CGH 244A, Illumina HumanExon510s-duo and Nimblegen HG18 CGH 385 k WG tiling v1.0. The data was analysed using the platform-specific analysis software, as well as a platform-independent analysis algorithm. DNA copy number was measured at six specific chromosomes or chromosomal regions, and compared with the expected ratio based on available cytogenetic information. All platforms performed well in terms of reproducibility and were able to delimit and score small amplifications and deletions at similar resolution, but Agilent microarrays showed better linearity and dynamic range. The platform-specific analysis software provided with each platform identified in general correct copy numbers, whereas using a platform-independent analysis algorithm, correct copy numbers were determined mainly for Agilent and Affymetrix microarrays.</p> <p>Conclusions</p> <p>All platforms performed reasonably well, but Agilent microarrays showed better dynamic range, and like Affymetrix microarrays performed well with the platform-independent analysis software, implying more robust data. Bone tumours like osteosarcomas are heterogeneous tumours with complex karyotypes that may be difficult to interpret, and it is of importance to be able to well separate the copy number levels and detect copy number changes in subpopulations. Taking all this into consideration, the Agilent and Affymetrix microarray platforms were found to be a better choice for mapping DNA copy numbers in bone tumours, the latter having the advantage of also providing heterozygosity information.</p

Impacto de la pizarra luminosa en estudiantes de contaduría pública de estadística inferencial y fundamentos de matemáticas.

Diagnosticar el uso de la pizarra luminosa en cursos cuantitativos.El uso de recursos que inviten al estudiante a estar más comprometido con su proceso educativo puede incrementar su desempeño. El objetivo del estudio es encontrar el nivel de apreciación percibido en el uso de la pizarra luminosa en dos cursos cuantitativos y establecer las diferencias entre el sexo y la situación laboral de los estudiantes participantes. Se utilizó como instrumento una encuesta que diligenciaron los 97 participantes. Se encontró que el 82% de los estudiantes preferían los videos elaborados por el mismo profesor que orientaba la asignatura, el 82% prefirió verle la cara al profesor mientras escribe en el tablero. En las 3 dimensiones, comprensión, compromiso y satisfacción, se obtuvo 97%, 94% y 95% respectivamente en la categoría “Totalmente de acuerdo”. La apreciación total en relación con el sexo no presentó diferencias significativas, al igual que con la situación laboral

Computational and neurobiological foundations of leadership decisions

Decisions as diverse as committing soldiers to the battlefield or picking a school for your child share a basic attribute: assuming responsibility for the outcome of others. This responsibility is inherent in the roles of prime ministers and generals, as well as in the more quotidian roles of firmmanagers, schoolteachers, and parents. Here we identify the underlying behavioral, computational, and neurobiologicalmechanisms that determine the choice to assume responsibility over others. Leaders must take responsibility for others and affect the well-being of individuals, organizations, and nations. We identify the effects of responsibility on leaders’ choices at the behavioral and neurobiological level and document the widespread existence of responsibility aversion, i.e., a reduced willingness to make decisions if the welfare of others is at stake. In mechanistic terms, basic preferences towards risk, losses and ambiguity do not explain responsibility aversion which, instead, is driven by a second-order cognitive process reflecting an increased demand for certainty about the best choice when others’ welfare is affected. Finally, models estimating levels of information flow between brain regions processing separate choice components, provide the first step in understanding the neurobiological basis of individual variability in responsibility aversion and leadership scores. We identify and characterize the computations and neural mechanisms underlying choices to lead

Contrasting Phaseolus crop water use patterns and stomatal dynamics in response to terminal drought

Terminal drought stress affects more than half of the areas planted with common bean (Phaseolus vulgaris), the main food legume globally, generating severe yield losses. Phenotyping water deficit responses and water use are central strategies to develop improved terminal drought resilience. The exploration and exploitation of genetic diversity in breeding programs are gaining importance, with a particular interest in related species with great adaptation to biotic and abiotic factors. This is the case with tepary beans (Phaseolus acutifolius), a bean that evolved and was domesticated in arid conditions and is considered well adapted to drought and heat stress. Under greenhouse conditions, using one genotype of tepary beans (resistant to drought) and two of common beans (one resistant and one susceptible to terminal drought), we evaluated phenotypic differences in traits such as water use efficiency (WUE), transpiration efficiency, rate of photosynthesis, photosynthetic efficiency, stomatal density, stomatal index, stomatal size, and the threshold for transpiration decline under well-watered and terminal drought conditions. Our results indicate two different water use strategies in drought-resistant genotypes: one observed in common bean aimed at conserving soil water by closing stomata early, inhibiting stomatal development, and limiting growth; and the other observed in tepary bean, where prolonged stomatal opening and higher carbon fixation, combined with no changes in stomata distribution, lead to higher biomass accumulation. Strategies that contribute to drought adaptation combined with other traits, such as greater mobilization of photoassimilates to the formation of reproductive structures, confer bean drought resistance and are useful targets in breeding programs

Morpho-physiological analysis of adaptive responses of common bean (Phaseolus vulgaris L.) to drought stress /

BibliografiaEl frijol común (Phaseolus vulgaris L.) es la leguminosa alimenticia más importante en los trópicos. Es cultivada por pequeños agricultores y por lo general expuesta a condiciones desfavorables con mínimo uso de insumos. La sequía y la baja fertilidad del suelo, especialmente deficiencias de nitrógeno (N) y fósforo (P), son principales limitaciones para el rendimiento del frijol en los sistemas de pequeños productores. El frijol puede derivar parte de su requerimiento de N de la atmósfera a través de la fijación simbiótica de nitrógeno (SNF). El estrés por sequía limita severamente la capacidad SNF de las plantas. Identificación de rasgos asociados con resistencia a sequía contribuye a mejorar el proceso de generación de genotipos de frijol adaptados a estas condiciones. Se realizaron ensayos de campo en el Centro Internacional de Agricultura Tropical (CIAT), Palmira, Colombia, para determinar la relación entre rendimiento de grano y diferentes parámetros morfo fisiológicos tales como uso efectivo del agua (EUW), biomasa dosel, removilización de fotosintatos (índice de partición vaina, índice de cosecha, índice de cosecha de vaina) y capacidad de SNF en líneas élites seleccionadas por resistencia a sequía durante la última década. También se validó la metodología de abundancia natural de 15N usando tejido de grano para cuantificar diferencias fenotípicas en la capacidad SNF y su aplicación en programas de mejoramiento. Se utilizó discriminación de isótopo de carbono (CID) para la estimación de uso eficiente del agua (WUE) y uso efectivo de agua (EUW). Se evaluaron 36 genotipos de frijol pertenecientes al acervo genético mesoamericano en condiciones de campo con dos niveles de suministro de agua (riego y sequía) en dos temporadas. Adicionalmente, se realizó un estudio en condiciones de invernadero utilizando cilindros de plástico con suelo, para determinar la relación entre rendimiento de grano y diferentes características morfo fisiológicas de raíz tales como la longitud total de raíces, producción de raíces finas y tasa de crecimiento visual de raíces. La resistencia a estrés por sequía se asoció positivamente con EUW, raíces profundas y vigorosas, mejor crecimiento de las plantas, y superior movilización de fotosintatos a la formación de vaina y granos; y negativamente con días a floración y días a madurez fisiológica. Basándose en diferencias fenotípicas obtenidas en CID, conductancia estomática, biomasa del dosel y rendimiento de grano en condiciones de sequía, las líneas evaluadas se clasificaron en dos grupos, los ahorradores y los gastadores de agua. Estos dos grupos también se diferenciaron en sus características de raíces, los gastadores de agua con un vigoroso y profundo sistema de raíces y los ahorradores con un moderado a superficial sistema de raíces con mayor presencia de raíces finas. Se utilizó el método de abundancia natural de 15N para comparar capacidad de SNF estimada convencionalmente usando tejido foliar vs tejido de grano. Los resultados mostraron una correlación positiva y significativa entre el nitrógeno derivado de la atmósfera (Ndfa) calculado utilizando tejido foliar y Ndfa usando el tejido de grano. El método usando grano mostró variabilidad fenotípica en la capacidad de SNF bajo condiciones de riego y sequía, y una reducción significativa en condiciones de sequía. Se recomienda usar este método en programas de mejoramiento de frijol para mejorar la capacidad SNF. Mejor habilidad SNF bajo estrés por sequía fue relacionada con presencia de raíces gruesas. Mayor absorción de nitrógeno del suelo fue asociado con un sistema de raíces fino y profundo. El índice de cosecha vaina, discriminación de isotopo de carbono y Ndfa usando tejido de grano podría ser criterios de selección útiles en los programas de mejoramiento para seleccionar frijol común con resistencia a la sequía.Common bean (Phaseolus vulgaris L.) is the most important food legume in the diet of poor people in the tropics. This legume is cultivated by small farmers and is usually exposed to unfavorable conditions with minimum use of inputs. Drought and low soil fertility, especially phosphorus (P) and nitrogen (N) deficiencies, are major limitations to bean yield in smallholder systems. Beans can derive part of their required N from the atmosphere through symbiotic nitrogen fixation (SNF). Drought stress severely limits SNF ability of plants. Identification of traits associated with drought resistance contributes to improving the process of designing bean genotypes adapted to these conditions. Field studies were conducted at the International Center for Tropical Agriculture (CIAT), Palmira, Colombia to determine the relationship between grain yield and different parameters in elite lines selected for drought resistance over the past decade. The selected traits were effective use of water (EUW), canopy biomass, remobilization of photosynthates to grain (pod partitioning index, harvest index and pod harvest index) and SNF ability. Moreover, in field trials we also validated the use of 15N natural abundance in grain tissue to quantify phenotypic differences in SNF ability for its implementation in breeding programs aiming to improve SNF in common bean. Carbon isotope discrimination (CID) was used for estimation of water use efficiency (WUE) and effective use of water (EUW). A set of 36 bean genotypes belonging to the Middle American gene pool were evaluated under field conditions with two levels of water supply (irrigated and rainfed) over two seasons. Additionally, a greenhouse study was conducted at CIAT using plastic cylinders with soil inserted into PVC pipes, to determine the relationship between grain yield and different root parameters such as total root length, fine root production and visual root growth rate in same group of elite lines under drought stress. Resistance to terminal drought stress was positively associated with EUW combined with a deeper and vigorous root system, better plant growth, and superior mobilization of photosynthates to pod and seed production, but negatively associated with days to flowering and days to physiological maturity. Based on phenotypic differences in CID, leaf stomatal conductance, canopy biomass and grain yield under drought stress, the tested lines were classified into two groups, water savers and water spenders. These groups also differ in their root characteristics, water spenders with a vigorous and deeper root system and water savers genotypes with a moderate to shallow root system and more presence of fine roots. We used 15N natural abundance method to compare SNF ability estimated from shoot tissue sampled at mid-pod filling growth stage vs. grain tissue sampled at harvest. The results showed a significant positive correlation between nitrogen derived from the atmosphere (Ndfa), estimated using shoot tissue at mid-pod filling, and Ndfa estimated using grain tissue at harvest. The method showed phenotypic variability in SNF ability under both drought and irrigated conditions. A significant reduction in SNF ability was observed under drought stress. We suggest that the method of estimating Ndfa using grain tissue (Ndfa-G) can be applied in bean breeding programs to improve SNF ability. Using this method of Ndfa-G, we identified bean lines that combine greater SNF ability with higher grain yield under drought stress. Better SNF ability under drought stress was related with superior presence of thick roots. Superior N uptake from the soil was associated with a large root system with more presence of fine roots. Pod harvest index, grain CID and Ndfa using grain tissue could be a useful selection criterion in breeding programs to select for drought resistance in common bean

Reorganizing the Intrinsic Functional Architecture of the Human Primary Motor Cortex during Rest with Non-Invasive Cortical Stimulation

The primary motor cortex (M1) is the main effector structure implicated in the generation of voluntary movements and is directly involved in motor learning. The intrinsic horizontal neuronal connections of M1 exhibit short-term and long-term plasticity, which is a strong substrate for learning-related map reorganization. Transcranial direct current stimulation (tDCS) applied for few minutes over M1 has been shown to induce relatively long-lasting plastic alterations and to modulate motor performance. Here we test the hypothesis that the relatively long-lasting synaptic modification induced by tDCS over M1 results in the alteration of associations among populations of M1 neurons which may be reflected in changes of its functional architecture. fMRI resting-state datasets were acquired immediately before and after 10 minutes of tDCS during rest, with the anode/cathode placed over the left M1. For each functional dataset, grey-matter voxels belonging to Brodmann area 4 (BA4) were labelled and afterwards BA4 voxel-based synchronization matrices were calculated and thresholded to construct undirected graphs. Nodal network parameters which characterize the architecture of functional networks (connectivity degree, clustering coefficient and characteristic path-length) were computed, transformed to volume maps and compared before and after stimulation. At the dorsolateral-BA4 region cathodal tDCS boosted local connectedness, while anodal-tDCS enhanced long distance functional communication within M1. Additionally, the more efficient the functional architecture of M1 was at baseline, the more efficient the tDCS-induced functional modulations were. In summary, we show here that it is possible to non-invasively reorganize the intrinsic functional architecture of M1, and to image such alterations