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

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Plant endocytosis: it is clathrin after all

Endocytosis occurs in plants, but the involvement of clathrin-coated vesicles has been unclear; a new study provides strong evidence that, as in animal cells, clathrin-coated vesicles are a major means of internalisation by plant cells.     

A source for category-induced global effects of feature-based attention in human prefrontal cortex

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时间选择性注意的认知神经机制

时间选择性注意是注意研究中开展较晚的一个领域,它是指通过有效的提示,将注意资源导向与即将到来的事件相关的时间点或时间窗的过程．回顾了时间选择性注意的行为及其认知神经机制的研究,并在与空间选择性注意比较的基础上,对热点问题和未来的研究趋势进行了分析．     

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.     

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.     

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.     

Enclosure choice and well‐being in giant pandas: is it all about control?

Behavioral and hormonal data were compared for four giant pandas in two management conditions: (1) panda confined to exhibit area and (2) panda given choice to move freely between exhibit and off‐exhibit bedroom areas. Pandas displayed fewer signs of behavioral agitation and lower urinary cortisol in the free choice condition. Time active did not differ between the two conditions. These results suggest that simply offering pandas free access to alternative locations can improve behavioral and hormonal variables that may be related to well‐being. Zoo Biol 0:1–7, 2005. © 2005 Wiley‐Liss, Inc.     

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.     

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.     

From bottom-up to top-down control of invertebrate herbivores in a retrogressive chronosequence

In the long-term absence of disturbance, ecosystems often enter a decline or retrogressive phase which leads to reductions in primary productivity, plant biomass, nutrient cycling and foliar quality. However, the consequences of ecosystem retrogression for higher trophic levels such as herbivores and predators, are less clear. Using a post-fire forested island-chronosequence across which retrogression occurs, we provide evidence that nutrient availability strongly controls invertebrate herbivore biomass when predators are few, but that there is a switch from bottom-up to top-down control when predators are common. This trophic flip in herbivore control probably arises because invertebrate predators respond to alternative energy channels from the adjacent aquatic matrix, which were independent of terrestrial plant biomass. Our results suggest that effects of nutrient limitation resulting from ecosystem retrogression on trophic cascades are modified by nutrient-independent variation in predator abundance, and this calls for a more holistic approach to trophic ecology to better understand herbivore effects on plant communities.     

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.     

Mismatch negativity of ERP in cross-modal attention

Event-related potentials were measured in 12 healthy youth subjects aged 19-22 using the paradigm "cross-modal and delayed response" which is able to improve unattended purity and to avoid the effect of task target on the deviant components of ERP. The experiment included two conditions: (i) Attend visual modality, ignore auditory modality; (ii) attend auditory modality, ignore visual modality. The stimuli under the two conditions were the same. The difference wave was obtained by subtracting ERPs of the standard stimuli from that of the deviant stim-uli. The present results showed that mismatch negativity (MMN), N2b and P3 components can be produced in the auditory and visual modalities under attention condition. However, only MMN was observed in the two modalities un-der inattention condition. Auditory and visual MMN have some features in common: their largest MMN wave peaks were distributed respectively over their primary sensory projection areas of the scalp under attention condition, but over front     

Electrophysiological evidence of personal experiences in the great Sichuan earthquake impacting on selective attention

Event-related brain potentials (ERPs) were measured when 24 Chinese subjects performed the earthquake color-matching Stroop task. All of them have experienced the great Sichuan earthquake (5.12), with 12 subjects in each of Chengdu city and Chongqing city (different earthquake experiences) groups. The behavioral data showed that the earthquake Stroop task yielded robust the earthquake interference effect as indexed by longer RT for earthquake-related (Related) words than earthquake-unrelated (Unrelated) words only in the Chengdu group. Scalp ERP analysis also revealed the neurophysiological substrate of the interference effect: a greater positivity (P350–450) in Related words as compared to Unrelated words was found between 350 and 450 ms post-stimulus over fronto-central scalp regions in the Chengdu group, while the interference effect was not found in the Chongqing group. The P350–450 might reflect an earthquake experience interference, but also attention enhancing, effect of earthquake-related words. Dipole source analysis of the difference wave (Related-Unrelated) showed that a generator was localized in the parahippocampal gyrus, which was possibly associated with flashbulb memory (personal earthquake experience). The results indicated that different personal earthquake experiences might be critical in engaging the neural mechanisms that underlie the modulation of selective attention. Supported by the National Natural Science Foundation of China (Grant No. 30800293), the Key Project of Philosophy and Social Science of Chinese Ministry of Education (Grant No. 08JZD0026), and the Southwest University Doctoral Fund.     

Cost of immune priming within generations: trade-off between infection and reproduction

Immune priming is a new paradigm in innate immunity. However, most studies have focused on the benefits of priming (enhanced survival and parasite clearance after a second challenge), while little attention has been paid to the costs. In this study, both factors were investigated in Anopheles albimanus primed against Plasmodium berghei. As previously observed in other invertebrates, compared to un-primed mosquitoes, those primed better controlled a challenge from the same parasite, and had a higher survival rate. Although there was no difference in the number of oviposited eggs between primed and control females, hatching rate was lower in primed than in control mosquitoes and it was more likely for control females to produce eggs than for primed females. Furthermore, a trade-off between parasite elimination and egg production was observed among primed mosquitoes, as primed females that successfully fought the infection were unable to produce eggs, but primed females that produced eggs were similarly infected as control un-primed ones. These results concord with recent mathematical models suggesting that reproduction affects immune priming outcomes, and may explain why in some species and under some conditions it seems that immune priming is not occurring.     

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.