Functional magnetic resonance imaging provides rich spatio-temporal data of human brain activity during task and rest. Many recent efforts have focussed on characterising dynamics of brain activity. One notable instance is co-activation pattern (CAP) analysis, a frame-wise analytical approach that disentangles the different functional brain networks interacting with a user-defined seed region. While promising applications in various clinical settings have been demonstrated, there is not yet any centralised, publicly accessible resource to facilitate the deployment of the technique.Here, we release a working version of TbCAPs, a new toolbox for CAP analysis, which includes all steps of the analytical pipeline, introduces new methodological developments that build on already existing concepts, and enables a facilitated inspection of CAPs and resulting metrics of brain dynamics. The toolbox is available on a public academic repository https://c4science.ch/source/CAP_ Toolbox.git.In addition, to illustrate the feasibility and usefulness of our pipeline, we describe an application to the study of human cognition. CAPs are constructed from resting-state fMRI using as seed the arXiv:1910.06113v1 [q-bio.QM]A PREPRINT -OCTOBER 15, 2019 right dorsolateral prefrontal cortex, and, in a separate sample, we successfully predict a behavioural measure of continuous attentional performance from the metrics of CAP dynamics (R=0.59).Keywords dynamic functional connectivity · frame-wise analysis · co-activation pattern analysis · task-positive network · attention · continuous performance · open source software In this work, in addition to the above, we propose an extension in which more than one seed region can be considered: for each seed j, a set of time points T s,j is derived. Assuming J separate seeds, one can then consider the time points when all seed time courses jointly take extreme values:
Tree species distributions associated with rainfall are among the most prominent patterns in tropical forests. Understanding the mechanisms shaping these patterns is important to project impacts of global climate change on tree distributions and diversity in the tropics. Beside direct effects of water availability, additional factors co-varying with rainfall have been hypothesized to play an important role, including pest pressure and light availability. While low water availability is expected to exclude drought-intolerant wet forest species from drier forests (physiological tolerance hypothesis), high pest pressure or low light availability are hypothesized to exclude dry forest species from wetter forests (pest pressure gradient and light availability hypothesis, respectively). To test these hypotheses at the seed-to-seedling transition, the potentially most critical stage for species discrimination, we conducted a reciprocal transplant experiment combined with a pest exclosure treatment at a wet and a dry forest site in Panama with seeds of 26 species with contrasting origin. Establishment success after one year did not reflect species distribution patterns. However, in the wet forest, wet origin species had a home advantage over dry forest species through higher growth rates. At the same time, drought limited survival of wet origin species in the dry forest, supporting the physiological tolerance hypothesis. Together these processes sort species over longer time frames, and exclude species outside their respective home range. Although we found pronounced effects of pests and some effects of light availability on the seedlings, they did not corroborate the pest pressure nor light availability hypotheses at the seed-to-seedling transition. Our results underline that changes in water availability due to climate change will have direct consequences on tree regeneration and distributions along tropical rainfall gradients, while indirect effects of light and pests are less important.
Aim Climate and habitat management are two key drivers for patterns of biodiversity, but little is known about relative importance, interactions and nonlinear effects of climate and management on species richness and trait variation of plants.Location Alps (Germany).Methods We studied patterns of species richness and pollination types in 34 alpine grasslands along an altitudinal climatic gradient comparing grazed, mown and non-managed grasslands. Two vegetation assessments were conducted in 2009 on ten 4-m² plots per study site and per survey.Results In total, 484 vascular plant species were recorded. Species richness peaked at intermediate temperatures and was highest in grazed grasslands compared with mown and non-managed grasslands. No significant interaction between management effects and climate was found. Species richness of insectpollinated plants peaked at lower temperatures (higher altitudes) than species richness of wind-pollinated plant species. The proportion of wind-pollinated plants decreased with decreasing temperature, but the vegetation cover of wind-pollinated plants increased with decreasing temperature. Main conclusionsOur results indicate that managing alpine grasslands by extensive grazing maintains high plant diversity over the full subalpine gradient. Rising temperatures with climate change and an upward shift of the diversity peak of plants might result not only in reduced overall diversity because of reduced grassland area at higher altitudes but also in changed species composition and adaptive potential of pollination types.
Abstract. Understanding the factors shaping species distribution patterns along tropical rainfall gradients is necessary to predict the consequences of climate change for tropical tree communities. Direct effects of water availability exclude wet forest species from dry forests, but the exclusion of dry forest species from wet forests remains unexplained. We tested the hypothesis that high light and nutrient requirements exclude dry forest species from dark, infertile, wet forests. We transplanted seedlings of 26 woody species to six sites along a pronounced regional rainfall gradient across the Isthmus of Panama. We examined the effects of soil moisture, phosphorus and light availability, and species' drought resistance on seedling performance, and linked the results directly to known species distribution patterns. Surprisingly, seedlings of wet forest species did not exhibit a home advantage: All species survived better under moister conditions, and the effects of phosphorus availability and light on seedling performance did not differ among species from dry or wet forests. Instead, dry forest species had intrinsically slower growth rates than wet forest species, which may lead to their exclusion from wet forests at later life history stages. High phosphorus exacerbated susceptibility to drought, although the mechanism remains unknown. Overall, our results demonstrate that seedling performance across tropical rainfall gradients is determined primarily by variation in soil water availability across space and time, while variation in nutrient and light availability plays a lesser role. Future changes in rainfall patterns will therefore have direct and pervasive consequences for forest composition and ecosystem function.
Carry‐over effects on brain states have been reported following emotional and cognitive events, persisting even during subsequent rest. Here, we investigated such effects by identifying recurring co‐activation patterns (CAPs) in neural networks at rest with functional magnetic resonance imaging (fMRI). We compared carry‐over effects on brain‐wide CAPs at rest and their modulation after both affective and cognitive challenges. Healthy participants underwent fMRI scanning during emotional induction with negative valence and performed cognitive control tasks, each followed by resting periods. Several CAPs, overlapping with the default‐mode (DMN), salience, dorsal attention, and social cognition networks were impacted by both the preceding events (movie or task) and the emotional valence of the experimental contexts (neutral or negative), with differential dynamic fluctuations over time. Temporal metrics of DMN‐related CAPs were altered after exposure to negative emotional content (compared to neutral) and predicted changes in subjective affect on self‐reported scores. In parallel, duration rates of another attention‐related CAP increased with greater task difficulty during the preceding cognitive control condition, specifically in the negative context. These findings provide new insights on the anatomical organization and temporal inertia of functional brain networks, whose expression is differentially shaped by emotional states, presumably mediating adaptive homeostatic processes subsequent to behaviorally challenging events.
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