Post-error recruitment of frontal sensory cortical projections promotes attention in mice

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Plankton dynamics in a tropical floodplain lake: fish, nutrients, and the relative importance of bottom-up and top-down control

1. Two enclosure experiments were carried out in Laguna Bufeos, a neotropical várzea lake located in the floodplain of River Ichilo (Bolivia). The experiments aimed (i) to assess the relative importance of bottom‐up and top‐down control on the plankton community, (ii) to assess the relative impact of direct and indirect effects of planktivorous fish on the zooplankton, and (iii) to attempt to identify the mechanisms responsible for these effects. 2. During the first experiment, bottom‐up control seemed to dominate the planktonic food web. Compared with fishless enclosures, oxygen concentrations, chlorophyll a levels and the population densities of all cladoceran zooplankton taxa increased in enclosures with fish. Birth rates of Moina minuta, the dominant taxon, were substantially higher in the presence than in the absence of fish, whereas death rates did not differ between treatments. These results are the first to suggest that the positive effects of fish on crustacean zooplankton via effects on nutrient cycling and the enhancement of primary production can compensate for losses because of fish‐related mortality. 3. During the second experiment, the direction of control appeared to vary between trophic levels: the phytoplankton appeared to be bottom‐up controlled whereas the zooplankton was mainly top‐down controlled. Chlorophyll a concentrations were enhanced by both fish and nutrient additions. The majority of the zooplankton taxa were reduced by the presence of fish. Birth rates of most cladoceran taxa did not differ between treatments, whereas death rates were higher in the enclosures with fish than in the fishless enclosures. Bosminopsis deitersi reached higher densities in the presence of fish, probably because of a release from predation by Chaoborus. 4. We convincingly showed strong deviations from trophic cascade‐based expectations, supporting the idea that trophic cascades may be weak in tropical lakes.     

Inter-hemispheric comparison of bottom-up effects on community structure: Insights revealed using the comparative-experimental approach

The comparative-experimental approach uses identically designed, replicated experiments at different sites along environmental gradients in order to gain insight into the changing dynamics of communities with changing environmental conditions. Such studies reveal how ecological processes vary in intensity and interact to produce community structure. Early emphases were on the community consequences of shifting top-down impacts, competition and disturbance with environmental stress. Recent advances include the more precise quantification of gradients and thus a better understanding of species responses to the environment, and the revelation that bottom-up forces can vary significantly on within-region scales, with major consequences for the impact of top-down forces and thus community dynamics. Here the use of the method to examine the role of geographic location (coastal ecosystems in different hemispheres) and oceanographic conditions (upwelling vs downwelling) on these bottom-up/top-down linkages is advanced. We show that a bottom-up factor (prey recruitment) and a top-down effect (predation rate) vary consistently with oceanographic conditions within each coastal ecosystem, and also between geographic locations (New Zealand, Oregon). In general, both recruitment and predation rates are higher in Oregon. It is postulated that these differences are common responses to oceanographic variation, and that between-hemisphere differences result from the stronger and more persistent upwelling in the California Current ecosystem.     

Autophagy in neurons: it is not all about food

The primary function of autophagy in most cell types is adaptation to starvation. Because neurons are protected from this type of stress, the physiological role of autophagy in normal functioning neurons was, until now, poorly understood. Using genetic manipulations to block autophagy in neurons selectively, Mizushima's and Tanaka's groups have recently presented conclusive evidence for an essential role of constitutive autophagy in neuronal survival. These studies provide new insights into the relationship between autophagy malfunctioning and neurodegenerative disorders.     

Looking on the bright side: biased attention and the human serotonin transporter gene

Humans differ in terms of biased attention for emotional stimuli and these biases can confer differential resilience and vulnerability to emotional disorders. Selective processing of positive emotional information, for example, is associated with enhanced sociability and well-being while a bias for negative material is associated with neuroticism and anxiety. A tendency to selectively avoid negative material might also be associated with mental health and well-being. The neurobiological mechanisms underlying these cognitive phenotypes are currently unknown. Here we show for the first time that allelic variation in the promotor region of the serotonin transporter gene (5-HTTLPR) is associated with differential biases for positive and negative affective pictures. Individuals homozygous for the long allele (LL) showed a marked bias to selectively process positive affective material alongside selective avoidance of negative affective material. This potentially protective pattern was absent among individuals carrying the short allele (S or SL). Thus, allelic variation on a common genetic polymorphism was associated with the tendency to selectively process positive or negative information. The current study is important in demonstrating a genotype-related alteration in a well-established processing bias, which is a known risk factor in determining both resilience and vulnerability to emotional disorders.     

Dissociation of category versus item priming in face processing: an event-related potential study

The underlying specificity of visual object categorization and discrimination can be elucidated by studying different types of repetition priming. Here we focused on this issue in face processing. We investigated category priming (i.e. the prime and target stimuli represent different exemplars of the same object category) and item priming (i.e. the prime and target stimuli are exactly the same image), using an immediate repetition paradigm. Twenty-three subjects were asked to respond as fast and accurately as possible to categorize whether the target stimulus was a face or a building image, but to ignore the prime stimulus. We recorded event-related potentials (ERPs) and reaction times (RTs) simultaneously. The RT data showed significant effects of category priming in both face trials and building trials, as well as a significant effect of item priming in face trials. With respect to the ERPs, in face trials, no priming effect was observed at the P100 stage, whereas a category priming effect emerged at the N170 stage, and an item priming effect at the P200 stage. In contrast, in building trials, priming effects occurred already at the P100 stage. Our results indicated that distinct neural mechanisms underlie separable kinds of immediate repetition priming in face processing.     

Positive emotional priming of facial affect perception in females is diminished by chemosensory anxiety signals

Chemosensory communication of anxiety is a common phenomenon in vertebrates and improves perceptual and responsive behaviour in the perceiver in order to optimize ontogenetic survival. A few rating studies reported a similar phenomenon in humans. Here, we investigated whether subliminal face perception changes in the context of chemosensory anxiety signals. Axillary sweat samples were taken from 12 males while they were waiting for an academic examination and while exercising ergometric training some days later. 16 subjects (eight females) participated in an emotional priming study, using happy, fearful and sad facial expressions as primes (11.7 ms) and neutral faces as targets (47 ms). The pooled chemosensory samples were presented before and during picture presentation (920 ms). In the context of chemosensory stimuli derived from sweat samples taken during the sport condition, subjects judged the targets significantly more positive when they were primed by a happy face than when they were primed by the negative facial expressions (P = 0.02). In the context of the chemosensory anxiety signals, the priming effect of the happy faces was diminished in females (P = 0.02), but not in males. It is discussed whether, in socially relevant ambiguous perceptual conditions, chemosensory signals have a processing advantage and dominate visual signals or whether fear signals in general have a stronger behavioural impact than positive signals.     

Predicting human visuomotor behaviour in a driving task

The sequential deployment of gaze to regions of interest is an integral part of human visual function. Owing to its central importance, decades of research have focused on predicting gaze locations, but there has been relatively little formal attempt to predict the temporal aspects of gaze deployment in natural multi-tasking situations. We approach this problem by decomposing complex visual behaviour into individual task modules that require independent sources of visual information for control, in order to model human gaze deployment on different task-relevant objects. We introduce a softmax barrier model for gaze selection that uses two key elements: a priority parameter that represents task importance per module, and noise estimates that allow modules to represent uncertainty about the state of task-relevant visual information. Comparisons with human gaze data gathered in a virtual driving environment show that the model closely approximates human performance.     

Motion-guided attention promotes adaptive communications during social navigation

Animals are capable of enhanced decision making through cooperation, whereby accurate decisions can occur quickly through decentralized consensus. These interactions often depend upon reliable social cues, which can result in highly coordinated activities in uncertain environments. Yet information within a crowd may be lost in translation, generating confusion and enhancing individual risk. As quantitative data detailing animal social interactions accumulate, the mechanisms enabling individuals to rapidly and accurately process competing social cues remain unresolved. Here, we model how motion-guided attention influences the exchange of visual information during social navigation. We also compare the performance of this mechanism to the hypothesis that robust social coordination requires individuals to numerically limit their attention to a set of n-nearest neighbours. While we find that such numerically limited attention does not generate robust social navigation across ecological contexts, several notable qualities arise from selective attention to motion cues. First, individuals can instantly become a local information hub when startled into action, without requiring changes in neighbour attention level. Second, individuals can circumvent speed–accuracy trade-offs by tuning their motion thresholds. In turn, these properties enable groups to collectively dampen or amplify social information. Lastly, the minority required to sway a group''s short-term directional decisions can change substantially with social context. Our findings suggest that motion-guided attention is a fundamental and efficient mechanism underlying collaborative decision making during social navigation.     

Selective attention to philopatric models causes directed social learning in wild vervet monkeys

Human behaviour is often based on social learning, a mechanism that has been documented also in a variety of other vertebrates. However, social learning as a means of problem-solving may be optimal only under specific conditions, and both theoretical work and laboratory experiments highlight the importance of a potential model''s identity. Here we present the results from a social learning experiment on six wild vervet monkey groups, where models were either a dominant female or a dominant male. We presented ‘artificial fruit’ boxes that had doors on opposite, differently coloured ends for access to food. One option was blocked during the demonstration phase, creating consistent demonstrations of one possible solution. Following demonstrations we found a significantly higher participation rate and same-door manipulation in groups with female models compared to groups with male models. These differences appeared to be owing to selective attention of bystanders to female model behaviour rather than owing to female tolerance. Our results demonstrate the favoured role of dominant females as a source for ‘directed’ social learning in a species with female philopatry. Our findings imply that migration does not necessarily lead to an exchange of socially acquired information within populations, potentially causing highly localized traditions.     

T cell priming by tissue-derived dendritic cells: new insights from recent murine studies

Dendritic cells (DCs) act as sentinels in peripheral tissues, continuously scavenging for antigens in their immediate surroundings. Their involvement in T cell responses is generally thought to consist of a linear progression of events, starting with capture of antigen in peripheral tissues such as the skin followed by migration to draining lymphoid organs and MHC-restricted presentation of antigen-derived peptide to induce T cell priming. The role of tissue-derived DCs in the direct priming of immune responses has lately been challenged. It now appears that, at least in some instances, a non-migratory subtype of DCs in the secondary lymphoid tissue presents tissue-derived antigen to T cells. Here, we review recent developments in research on DC function in the priming of immune responses.     

Social orienting in gaze leading: a mechanism for shared attention

Here, we report a novel social orienting response that occurs after viewing averted gaze. We show, in three experiments, that when a person looks from one location to an object, attention then shifts towards the face of an individual who has subsequently followed the person''s gaze to that same object. That is, contrary to ‘gaze following’, attention instead orients in the opposite direction to observed gaze and towards the gazing face. The magnitude of attentional orienting towards a face that ‘follows’ the participant''s gaze is also associated with self-reported autism-like traits. We propose that this gaze leading phenomenon implies the existence of a mechanism in the human social cognitive system for detecting when one''s gaze has been followed, in order to establish ‘shared attention’ and maintain the ongoing interaction.     

Dynamics of the semantic priming shift: behavioral experiments and cortical network model

Multiple semantic priming processes between several related and/or unrelated words are at work during the processing of sequences of words. Multiple priming generates rich dynamics of effects depending on the relationship between the target word and the first and/or second prime previously presented. The experimental literature suggests that during the on-line processing of the primes, the activation can shift from associates to the first prime to associates to the second prime. Though the semantic priming shift is central to the on-line and rapid updating of word meanings in the working memory, its precise dynamics are still poorly understood and it is still a challenge to model how it functions in the cerebral cortex. Four multiple priming experiments are proposed that cross-manipulate delays and association strength between the primes and the target. Results show for the first time that association strength determines complex dynamics of the semantic priming shift, ranging from an absence of a shift to a complete shift. A cortical network model of spike frequency adaptive neuron populations is proposed to account for the non-continuous evolution of the priming shift over time. It allows linking the dynamics of the priming shift assessed at the behavioral level to the non-linear dynamics of the firing rates of neurons populations.     

The Field Studies Council: how it all began

The Field Studies Council (or the Council for the Promotion of Field Studies as it was originally called) had its beginnings in the need for residential training in field studies directed by a London County Council schools inspector, Francis Butler. It was founded at a meeting held in the British Museum (Natural History) on 10 September 1943; Sir Arthur Tansley was the first President and Sir Maurice Yonge the first Chairman. The first centres were managed on a do-your-best basis when food was rationed and building materials almost unobtainable by a remarkable generation of Wardens, chronically starved of funds. The excitement and vision of the early days kept the Council alive, but its survival was repeatedly in doubt for the first decade of its existence.     

ADAM-17: the enzyme that does it all

This review focuses on the role of ADAM-17 in disease. Since its debut as the tumor necrosis factor converting enzyme (TACE), ADAM-17 has been reported to be an indispensible regulator of almost every cellular event from proliferation to migration. The central role of ADAM-17 in cell regulation is rooted in its diverse array of substrates: cytokines, growth factors, and their receptors as well as adhesion molecules are activated or inactivated by their cleavage with ADAM-17. It is therefore not surprising that ADAM-17 is implicated in numerous human diseases including cancer, heart disease, diabetes, rheumatoid arthritis, kidney fibrosis, Alzheimer’s disease, and is a promising target for future treatments. The specific role of ADAM-17 in the pathophysiology of these diseases is very complex and depends on the cellular context. To exploit the therapeutic potential of ADAM-17, it is important to understand how its activity is regulated and how specific organs and cells can be targeted to inactivate or activate the enzyme.     

'Well doctor, it is all about how life is lived': cues as a tool in the medical consultation

Introduction During consultations, the perspective of the patient and the family physician come together. In order to reach a shared view about the symptoms it is important to know the agenda of the patient. Cues (i.e. non-explicit remarks that can enclose a special meaning) can serve as a tool to clarify the agenda.Case report In this article, we describe a patient with unexplained palpitations during vacuuming. During one of the following consultations she provided an important psychosocial cue which changed my perspective on her palpitations, resulting in a deeper understanding of her symptoms.Discussion Recognition and exploration of cues is important for reaching mutual understanding of doctors and patients about the symptoms. Moreover, it enhances the therapeutic relationship and improves illness outcomes and patient satisfaction.Conclusion Noticing cues in the medical consultation helps the doctor to understand the patient's real worries. It gives us, as doctors, a better understanding of the patient's perspective.     

The forest or the trees: preference for global over local image processing is reversed by prior experience in honeybees

Traditional models of insect vision have assumed that insects are only capable of low-level analysis of local cues and are incapable of global, holistic perception. However, recent studies on honeybee (Apis mellifera) vision have refuted this view by showing that this insect also processes complex visual information by using spatial configurations or relational rules. In the light of these findings, we asked whether bees prioritize global configurations or local cues by setting these two levels of image analysis in competition. We trained individual free-flying honeybees to discriminate hierarchical visual stimuli within a Y-maze and tested bees with novel stimuli in which local and/or global cues were manipulated. We demonstrate that even when local information is accessible, bees prefer global information, thus relying mainly on the object''s spatial configuration rather than on elemental, local information. This preference can be reversed if bees are pre-trained to discriminate isolated local cues. In this case, bees prefer the hierarchical stimuli with the local elements previously primed even if they build an incorrect global configuration. Pre-training with local cues induces a generic attentional bias towards any local elements as local information is prioritized in the test, even if the local cues used in the test are different from the pre-trained ones. Our results thus underline the plasticity of visual processing in insects and provide new insights for the comparative analysis of visual recognition in humans and animals.     

Fundamental Differences in Visual Perceptual Learning between Children and Adults

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How it all starts: Initiation of the clotting cascade

Abstract

The plasma coagulation system in mammalian blood consists of a cascade of enzyme activation events in which serine proteases activate the proteins (proenzymes and procofactors) in the next step of the cascade via limited proteolysis. The ultimate outcome is the polymerization of fibrin and the activation of platelets, leading to a blood clot. This process is protective, as it prevents excessive blood loss following injury (normal hemostasis). Unfortunately, the blood clotting system can also lead to unwanted blood clots inside blood vessels (pathologic thrombosis), which is a leading cause of disability and death in the developed world. There are two main mechanisms for triggering the blood clotting, termed the tissue factor pathway and the contact pathway. Only one of these pathways (the tissue factor pathway) functions in normal hemostasis. Both pathways, however, are thought to contribute to thrombosis. An emerging concept is that the contact pathway functions in host pathogen defenses. This review focuses on how the initiation phase of the blood clotting cascade is regulated in both pathways, with a discussion of the contributions of these pathways to hemostasis versus thrombosis.     

The behavioral ecology of a cognitive constraint: limited attention

Limited attention may constrain animal behavior in situationsin which the rate of relevant information exceeds the thresholdprocessing capacity of the brain. In the present study, we examinewhy attention is limited by quantifying how attention affectsthe ubiquitous problem of balancing foraging and antipredatoractivity. We analyze how a given attentional capacity affectsfeeding requirements, the optimal attentional focus during predatorscanning, and the probability of detecting predators. Our modelindicates that because of the complex interplay between thecosts and benefits associated with a given attentional capacity,limited attention can be an optimal strategy, which allows effectiveand economical search for cryptic objects.