Overdispersion is common in models of count data in ecology and evolutionary biology, and can occur due to missing covariates, non-independent (aggregated) data, or an excess frequency of zeroes ...(zero-inflation). Accounting for overdispersion in such models is vital, as failing to do so can lead to biased parameter estimates, and false conclusions regarding hypotheses of interest. Observation-level random effects (OLRE), where each data point receives a unique level of a random effect that models the extra-Poisson variation present in the data, are commonly employed to cope with overdispersion in count data. However studies investigating the efficacy of observation-level random effects as a means to deal with overdispersion are scarce. Here I use simulations to show that in cases where overdispersion is caused by random extra-Poisson noise, or aggregation in the count data, observation-level random effects yield more accurate parameter estimates compared to when overdispersion is simply ignored. Conversely, OLRE fail to reduce bias in zero-inflated data, and in some cases increase bias at high levels of overdispersion. There was a positive relationship between the magnitude of overdispersion and the degree of bias in parameter estimates. Critically, the simulations reveal that failing to account for overdispersion in mixed models can erroneously inflate measures of explained variance (r (2)), which may lead to researchers overestimating the predictive power of variables of interest. This work suggests use of observation-level random effects provides a simple and robust means to account for overdispersion in count data, but also that their ability to minimise bias is not uniform across all types of overdispersion and must be applied judiciously.
•Difficulties in non-verbal communication may underlie the social disability reported by people with eating disorders (EDs)•This was the first study to investigate non-verbal communication during a ...real-life social interaction in people with EDs compared to non-ED controls•People with EDs make less use of hand gestures and show different body posture than controls during social interaction.•There is no difference in facially-expressed emotions during social interaction between those with EDs and controls.•People show less physiological arousal than controls during social interaction.
This study aimed to be the first to measure non-verbal communication in 25 eating disorder (ED) and 25 non-ED control participants during a naturalistic social interaction incorporating positive, negative and neutrally-valenced topics. The first hypothesis, that ED participants would show significantly reduced facial emotional expression than controls, was not supported. Supporting the second hypothesis of between-group differences in non-verbal behaviour, ED participants were less likely to lean in towards their interlocutor (d=.81) discussing negatively-valanced topics and were more likely to be positioned upright when discussing positively-valenced topics (d=.1.09) than controls. Irrespective of emotional valence, ED participants positioned their gaze on their interlocutor significantly less (d=.29) and spent more time looking down (d=.54), or away than controls (d=.63). ED participants moved their hands along with speech significantly less (d=.63) and gestured fewer real/hypothetical/imagined images/actions/objects) than controls (d=.57), irrespective of emotional valence. Instead, ED participants indicated discomfort in the social interaction, touching their nose (d=.89) or playing with their nails (d=.95) more often than controls. ED participants, regardless of emotional valence, showed significantly lowered electro-dermal activity (d=.60) than controls, supporting the exploratory hypothesis. People with EDs appear to make less efficient use of non-verbal communication than controls.
Overdispersion is a common feature of models of biological data, but researchers often fail to model the excess variation driving the overdispersion, resulting in biased parameter estimates and ...standard errors. Quantifying and modeling overdispersion when it is present is therefore critical for robust biological inference. One means to account for overdispersion is to add an observation-level random effect (OLRE) to a model, where each data point receives a unique level of a random effect that can absorb the extra-parametric variation in the data. Although some studies have investigated the utility of OLRE to model overdispersion in Poisson count data, studies doing so for Binomial proportion data are scarce. Here I use a simulation approach to investigate the ability of both OLRE models and Beta-Binomial models to recover unbiased parameter estimates in mixed effects models of Binomial data under various degrees of overdispersion. In addition, as ecologists often fit random intercept terms to models when the random effect sample size is low (<5 levels), I investigate the performance of both model types under a range of random effect sample sizes when overdispersion is present. Simulation results revealed that the efficacy of OLRE depends on the process that generated the overdispersion; OLRE failed to cope with overdispersion generated from a Beta-Binomial mixture model, leading to biased slope and intercept estimates, but performed well for overdispersion generated by adding random noise to the linear predictor. Comparison of parameter estimates from an OLRE model with those from its corresponding Beta-Binomial model readily identified when OLRE were performing poorly due to disagreement between effect sizes, and this strategy should be employed whenever OLRE are used for Binomial data to assess their reliability. Beta-Binomial models performed well across all contexts, but showed a tendency to underestimate effect sizes when modelling non-Beta-Binomial data. Finally, both OLRE and Beta-Binomial models performed poorly when models contained <5 levels of the random intercept term, especially for estimating variance components, and this effect appeared independent of total sample size. These results suggest that OLRE are a useful tool for modelling overdispersion in Binomial data, but that they do not perform well in all circumstances and researchers should take care to verify the robustness of parameter estimates of OLRE models.
Pelagic marine predators face unprecedented challenges and uncertain futures. Overexploitation and climate variability impact the abundance and distribution of top predators in ocean ecosystems. ...Improved understanding of ecological patterns, evolutionary constraints and ecosystem function is critical for preventing extinctions, loss of biodiversity and disruption of ecosystem services. Recent advances in electronic tagging techniques have provided the capacity to observe the movements and long-distance migrations of animals in relation to ocean processes across a range of ecological scales. Tagging of Pacific Predators, a field programme of the Census of Marine Life, deployed 4,306 tags on 23 species in the North Pacific Ocean, resulting in a tracking data set of unprecedented scale and species diversity that covers 265,386 tracking days from 2000 to 2009. Here we report migration pathways, link ocean features to multispecies hotspots and illustrate niche partitioning within and among congener guilds. Our results indicate that the California Current large marine ecosystem and the North Pacific transition zone attract and retain a diverse assemblage of marine vertebrates. Within the California Current large marine ecosystem, several predator guilds seasonally undertake north-south migrations that may be driven by oceanic processes, species-specific thermal tolerances and shifts in prey distributions. We identify critical habitats across multinational boundaries and show that top predators exploit their environment in predictable ways, providing the foundation for spatial management of large marine ecosystems.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mental processes and their neural substrates are intimately linked to the homeostatic control of internal bodily state. There are a set of distinct interoceptive pathways that directly and indirectly ...influence brain functions. The anatomical organization of these pathways and the psychological/behavioral expressions of their influence appear along discrete, evolutionarily conserved dimensions that are tractable to a mechanistic understanding. Here, we review the role of these pathways as sources of biases to perception, cognition, emotion, and behavior and arguably the dynamic basis to the concept of self.
In this issue, Critchley and Harrison review the influence of interoceptive pathways, which deliver information on the body’s physiological state, on brain function, including perception, cognition, emotion, and behavior.
We conduct a comprehensive synthesis of the research on how female representation in the upper echelons (i.e., top management teams and chief executive officer positions) might affect firm ...performance. To help resolve longstanding theoretical, empirical, and substantive debates, we present an integrative conceptual framework based on the overarching concepts of unique resource portfolios, team decision-processes, and role incongruence perceptions. We test predictions from this framework using meta-analytic techniques on a sample of 146 primary studies conducted in 33 different countries. We find that female representation in the upper echelons in general is positively and weakly related to forms of long-term financial performance, but negatively and weakly related to short-term stock market returns. We observe that reduced strategic risk-taking is a mediating mechanism that explains why financial performance is improved. We also show that financial performance improvements are accentuated in environmental and organizational contexts that provide greater decision latitude to executives. Finally, we discuss and provide preliminary tests for extending these effects to other stakeholders (corporate social performance) and different time intervals for performance.
The Jak/STAT pathway Harrison, Douglas A
Cold Spring Harbor perspectives in biology,
2012-Mar-01, 2012-03-01, 20120301, Letnik:
4, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway mediates cellular responses to cytokines (e.g., IL-6) and growth factors (e.g., EGF).
Visual working memory provides an essential link between perception and higher cognitive functions, allowing for the active maintenance of information about stimuli no longer in view. Research ...suggests that sustained activity in higher-order prefrontal, parietal, inferotemporal and lateral occipital areas supports visual maintenance, and may account for the limited capacity of working memory to hold up to 3-4 items. Because higher-order areas lack the visual selectivity of early sensory areas, it has remained unclear how observers can remember specific visual features, such as the precise orientation of a grating, with minimal decay in performance over delays of many seconds. One proposal is that sensory areas serve to maintain fine-tuned feature information, but early visual areas show little to no sustained activity over prolonged delays. Here we show that orientations held in working memory can be decoded from activity patterns in the human visual cortex, even when overall levels of activity are low. Using functional magnetic resonance imaging and pattern classification methods, we found that activity patterns in visual areas V1-V4 could predict which of two oriented gratings was held in memory with mean accuracy levels upwards of 80%, even in participants whose activity fell to baseline levels after a prolonged delay. These orientation-selective activity patterns were sustained throughout the delay period, evident in individual visual areas, and similar to the responses evoked by unattended, task-irrelevant gratings. Our results demonstrate that early visual areas can retain specific information about visual features held in working memory, over periods of many seconds when no physical stimulus is present.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Pharmacotherapy for NASH: Current and emerging Konerman, Monica A.; Jones, Jacob C.; Harrison, Stephen A.
Journal of hepatology,
February 2018, 2018-02-00, 20180201, Letnik:
68, Številka:
2
Journal Article
Recenzirano
Non-alcoholic fatty liver disease (NAFLD) has become one of the most prominent forms of chronic liver disease worldwide, reflecting the epidemic of global obesity. Those with the progressive variant ...of NAFLD, non-alcoholic steatohepatitis (NASH), are at significantly increased risk of multisystem morbidity and mortality. However, there are currently no approved pharmacologic therapies for NASH. Given the disease burden, there is an important unmet need for pharmacologic treatment options for this patient population. The underlying pathophysiologic mechanisms that contribute to the development and progression of NAFLD and NASH are complex and reflected by the myriad of therapies, with different targets, currently under investigation. In broad strokes, drug development has focused on modulation of metabolic pathways, inflammatory cascades, and/or mechanisms impacting fibrosis. Although much progress has been made in enhancing our understanding of NAFLD pathogenesis, development of pharmacologic treatments has been hindered by challenges in clinical trial enrollment and complexities in clinical trial design. The compounds in phase IIa have provided promising results in terms of potential benefits on various aspects of histopathology. Agents in later stages of development have shown fairly modest results in terms of reduction of hepatic steatosis, necroinflammation and fibrosis. If longer term safety and efficacy are established among heterogeneous cohorts, these medications may help mitigate potential morbidity and mortality for this burgeoning patient population.
Patients with nonalcoholic steatohepatitis were randomly assigned to receive subcutaneous semaglutide or placebo. The incidence of NASH resolution was significantly higher with semaglutide than with ...placebo, but the between-group difference in the incidence of an improvement in fibrosis stage was not significant.
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