Human behavior emerges from planning over elaborate decompositions of tasks into goals, subgoals, and low-level actions. How are these decompositions created and used? Here, we propose and evaluate a ...normative framework for task decomposition based on the simple idea that people decompose tasks to reduce the overall cost of planning while maintaining task performance. Analyzing 11,117 distinct graph-structured planning tasks, we find that our framework justifies several existing heuristics for task decomposition and makes predictions that can be distinguished from two alternative normative accounts. We report a behavioral study of task decomposition (N = 806) that uses 30 randomly sampled graphs, a larger and more diverse set than that of any previous behavioral study on this topic. We find that human responses are more consistent with our framework for task decomposition than alternative normative accounts and are most consistent with a heuristic-betweenness centrality-that is justified by our approach. Taken together, our results suggest the computational cost of planning is a key principle guiding the intelligent structuring of goal-directed behavior.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
One of the most striking features of human cognition is the ability to plan. Two aspects of human planning stand out-its efficiency and flexibility. Efficiency is especially impressive because plans ...must often be made in complex environments, and yet people successfully plan solutions to many everyday problems despite having limited cognitive resources
. Standard accounts in psychology, economics and artificial intelligence have suggested that human planning succeeds because people have a complete representation of a task and then use heuristics to plan future actions in that representation
. However, this approach generally assumes that task representations are fixed. Here we propose that task representations can be controlled and that such control provides opportunities to quickly simplify problems and more easily reason about them. We propose a computational account of this simplification process and, in a series of preregistered behavioural experiments, show that it is subject to online cognitive control
and that people optimally balance the complexity of a task representation and its utility for planning and acting. These results demonstrate how strategically perceiving and conceiving problems facilitates the effective use of limited cognitive resources.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Purpose
. Lymphopenia is a common side effect in patients treated with radiotherapy, potentially caused by direct cell killing of circulating lymphocytes in the blood. To investigate this ...hypothesis, a method to assess dose to circulating lymphocytes is needed.
Methods
. A stochastic model to simulate systemic blood flow in the human body was developed based on a previously designed compartment model. Blood dose was obtained by superimposing the spatiotemporal distribution of blood particles with a time-varying dose rate field, and used as a surrogate for dose to circulating lymphocytes. We discuss relevant theory on compartmental modeling and how to combine it with models of explicit organ vasculature.
Results
. A general workflow was established which can be used for any anatomical site. Stochastic compartments can be replaced by explicit models of organ vasculatures for improved spatial resolution, and tumor compartments can be dynamically assigned. Generating a patient-specific blood flow distribution takes about one minute, fast enough to investigate the effect of varying treatment parameters such as the dose rate. Furthermore, the anatomical structures contributing most to the overall blood dose can be identified, which could potentially be used for lymphocyte-sparing treatment planning.
Conclusion
. The ability to report the blood dose distribution during radiotherapy is imperative to test and act upon the current paradigm that radiation-induced lymphopenia is caused by direct cell killing of lymphocytes in the blood. We have built a general model that can do so for various treatment sites. The presented framework is publicly available at
http://github.com/mghro/hedos
.
The purpose of this study was to evaluate the impact of Chlorella vulgaris (5% in the diet), supplemented or not with two exogenous carbohydrase mixtures on piglets' performance, nutrient ...digestibility and gut morphology, fermentation products and microbiota. Forty-four male piglets weaned at 28 days of age, with 11.2 ± 0.46 kg of live weight, were used and assigned to 1 of 4 dietary treatments: cereal and soybean meal based-diet (control, n = 11), control diet with 5% of C. vulgaris (CH, n = 10), CH diet supplemented with 0.005% of Rovabio
Excel AP (CH + R, n = 10) and CH diet supplemented with 0.01% of a recombinant 4-carbohydrase mixture (CH + M, n = 11). Growth performance was not changed by the of C. vulgaris inclusion during 21 days of trial. However, total tract apparent digestibility of nutritional fractions was negatively impacted by the inclusion. In addition, the viscosity of duodenum plus jejunum contents slightly increased in all groups fed with the microalga. In contrast, dietary microalga increased duodenum villus height and promoted a healthier gut microbiota, with higher abundance of some specific bacterial taxa (Colidextribacter, Oscillospira and Lactobacillus). This study indicates that the dietary inclusion of 5% C. vulgaris improves piglets' gut health without impairing performance. Data also indicate that C. vulgaris reduces nutrient digestibility but promotes compensatory developments of gut mucosa and prebiotic effects. Dietary supplementation with exogenous carbohydrases does not seem to be necessary for this inclusion level. Therefore, the incorporation of CH as a sustainable feed ingredient in piglets' nutrition is a viable alternative approach.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Depression exerts a staggering toll that is worsened with co-occurring chronic conditions such as obesity. It is imperative to develop more effective interventions for depression and to identify ...objective and biological plausible neural mechanisms to understand intervention outcomes. The current study uses functional neuroimaging to determine whether a behavioural intervention changes the negative affect circuit and whether these changes relate to subsequent improvements in both symptom and problem-solving outcomes in depressed patients with co-occurring obesity.
This study (‘ENGAGE’) was a pre-planned element of the randomized controlled trial, ‘RAINBOW’ (ClinicalTrials.gov NCT02246413). 108 depressed patients with obesity were randomized to receive an integrated collaborative care intervention (I-CARE) or usual care. Participants underwent functional neuroimaging using an established facial emotion task at baseline and two months (coinciding with the first two months of intervention focused on problem-solving therapy (‘PST’)). Amygdala, insula and anterior cingulate cortex activation was extracted using pre-planned definitions and standardized methods. The primary health and behavioural outcomes were depression symptom severity and problem-solving ability respectively, assessed at baseline, the main 6-month outcome point and at 12-month follow up. Mediation analyses used an intent-to-treat approach.
PST, relative to usual care, reduced amygdala activation engaged by threat stimuli at two months. This reduction mediated subsequent improvements in depression severity in an intervention-dependent manner. PST did not change insula activation at two months but did temper the strength of the relationship between insula activation and improvements in problem-solving ability.
The negative affect circuit may be an important neural target and potential mediator of PST in patients with comorbid obesity.
US National Institutes of Health/National Heart Lung and Blood Institute R01 HL119453 and UH2/UH3 HL132368
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Small RNAs (sRNAs) are a class of non-coding RNAs ranging from 20- to 40-nucleotides (nts) that are present in most eukaryotic organisms. In plants, sRNAs are involved in the regulation of ...development, the maintenance of genome stability and the antiviral response. Viruses, however, can interfere with and exploit the silencing-based regulatory networks, causing the deregulation of sRNAs, including small interfering RNAs (siRNAs) and microRNAs (miRNAs). To understand the impact of viral infection on the plant sRNA pathway, we deep sequenced the sRNAs in cotton leaves infected with Cotton leafroll dwarf virus (CLRDV), which is a member of the economically important virus family
Luteoviridae
. A total of 60 putative conserved cotton miRNAs were identified, including 19 new miRNA families that had not been previously described in cotton. Some of these miRNAs were clearly misregulated during viral infection, and their possible role in symptom development and disease progression is discussed. Furthermore, we found that the 24-nt heterochromatin-associated siRNAs were quantitatively and qualitatively altered in the infected plant, leading to the reactivation of at least one cotton transposable element. This is the first study to explore the global alterations of sRNAs in virus-infected cotton plants. Our results indicate that some CLRDV-induced symptoms may be correlated with the deregulation of miRNA and/or epigenetic networks.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Understanding how environmental drivers induce changes in plant composition and diversity across evolutionary time can provide important insights into community assembly mechanisms. We evaluated how ...taxonomic and phylogenetic diversity and structure of plant communities change along a local-scale edaphic and elevational gradient in the Tepequém table mountain, Brazilian Amazon. We selected three phytophysiognomies along the altitudinal gradient: Open Rupestrian Grassland, Shrubby Rupestrian Grassland, and Forest. We compared community composition and taxonomic and phylogenetic diversity between phytophysiognomies, and analysed effects of altitude and soil properties on species richness and phylogenetic metrics using linear mixed-effects models. The highest species richness and phylogenetic diversity were found at a lower elevation for Forest. All standardised phylogenetic metrics were significantly lower in Shrubby Rupestrian Grassland. This phytophysiognomy showed phylogenetic clustering. Forest showed a cluster pattern when only terminal nodes are considered and random dispersion to deep phylogenetic nodes. Open Rupestrian Grassland also showed a random phylogenetic structure. The linear mixed-effects models showed that species richness and different phylogenetic structure metrics were explained by altitude and soil properties. Our study revealed that key plant diversity dimensions (i.e. taxonomic and phylogenetic) are shaped by a local-scale edaphic and elevational gradient on an isolated
tepui
of Brazilian Amazonian.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Vegetation and soil properties of an iron-rich canga (laterite) island on the largest outcrop of banded-iron formation in Serra de Carajás (eastern Amazonia, Brazil) were studied along a topographic ...gradient (738-762 m asl), and analyzed to test the hypothesis that soil chemical and physical attributes play a key role in the structure and floristic composition of these plant communities. Soil and vegetation were sampled in eight replicate plots within each of the four vegetation types. Surface (0-10 cm) soil samples from each plot were analyzed for basic cations, N, P and plant species density for all species was recorded. CCA ordination analysis showed a strong separation between forest and non-forest sites on the first axis, and between herbaceous and shrubby campo rupestre on the second axis. The four vegetation types shared few plant species, which was attributed to their distinctive soil environments and filtering of their constituent species by chemical, physical and hydrological constraints. Thus, we can infer that Edaphic (pedological) factors are crucial in explaining the types and distributions of campo rupestre vegetation associated with ferruginous ironstone uplands (Canga) in Carajás, eastern Amazonia, therefore the soil properties are the main drivers of vegetation composition and structure on these ironstone islands.
Vegetação e propriedades do solo de uma ilha de canga rica em ferro (laterita) no maior afloramento de formação ferrífera bandada, na Serra de Carajás (Amazônia oriental, Brasil), foram estudados, ao longo de um gradiente topográfico (738-762 m de altitude), e analisados para testar a hipótese de que os atributos químicos e físicos do solo desempenham um papel fundamental na estrutura e composição florística destas comunidades vegetais. Solos e vegetação foram amostrados em oito parcelas replicadas dentro de cada um dos quatro tipos de vegetação. Amostras de solo superficiais (0-10 cm) de cada parcela foram analisadas para cátions básicos, N, P e densidade de espécies de plantas para todas as espécies foram registradas. Análise de ordenação CCA evidenciou uma forte separação entre áreas florestais e não florestais no primeiro eixo, e entre campo rupestre herbáceo e arbustivo no segundo eixo. Os quatro tipos de vegetação compartilham poucas espécies de plantas, o que pode ser atribuído aos seus ambientes de solos distintos e filtragem de suas espécies constituintes por limitações químicas, físicas e hidrológicas. Assim, podemos inferir que fatores edáficos (pedológicos) são cruciais para explicar os tipos e distribuições da vegetação dos campos rupestres associados com platôs ferruginosos (Canga), em Carajás, no leste da Amazônia, sendo, portanto, as propriedades do solo as principais condutoras da composição e estrutura da vegetação nestas ilhas ferríferas.
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