The right temporo-parietal junction (TPJ) is widely considered as part of a network that reorients attention to task-relevant, but currently unattended stimuli (Corbetta and Shulman, 2002). Despite ...the prevalence of this theory in cognitive neuroscience, there is little direct evidence for the principal hypothesis that TPJ sends an early reorientation signal that "circuit breaks" attentional processing in regions of the dorsal attentional network (e.g., the frontal eye fields) or is completely right lateralized during attentional processing. In this review, we examine both functional neuroimaging work on TPJ in the attentional literature as well as anatomical findings. We first critically evaluate the idea that TPJ reorients attention and is right lateralized; we then suggest that TPJ signals might rather reflect post-perceptual processes involved in contextual updating and adjustments of top-down expectations; and then finally discuss how these ideas relate to the electrophysiological (P300) literature, and to TPJ findings in other cognitive and social domains. We conclude that while much work is needed to define the computational functions of regions encapsulated as TPJ, there is now substantial evidence that it is not specialized for stimulus-driven attentional reorienting.
Attentional Mechanisms of Distractor Suppression Geng, Joy J.
Current directions in psychological science : a journal of the American Psychological Society,
04/2014, Letnik:
23, Številka:
2
Journal Article
Recenzirano
The ability to suppress distractors is critical for the successful completion of goal-oriented behaviors. This is particularly true for everyday behaviors that take time to accomplish and are ...frequently interrupted by unpredicted events (e.g., spotting a sale on a favorite drink while searching a grocery store for an apple). For one to continue with the intended goal, attention to the distractor must be reactively suppressed (i.e., terminated) so that the goal-oriented behavior may resume. Such reactive suppression can be contrasted with a proactive mechanism that anticipates the appearance of a distractor and suppresses related sensory processing in advance. In this review, I consider three aspects of distractor suppression: (a) the distinction between proactive and reactive mechanisms, (b) the conditions under which reactive distractor rejection can be rapid, and (c) the neural and cognitive processes necessary for controlling proactive and reactive distractor suppression.
Much is known about the mechanisms by which attention is focused to facilitate perception, but little is known about what happens to attention after perception of the attended object is complete. One ...possibility is that the focus of attention passively fades. A second possibility is that attention is actively terminated after the completion of perception so that the brain can be prepared for the next target. The present study investigated this issue with event-related potentials in humans, focusing on the N2pc component (a neural measure of attentional deployment) and the Pd component (a neural measure of attentional suppression). We found that active suppression occurred both to prevent the allocation of attention to known distractors and to terminate attention after the perception of an attended object was complete. In addition, the neural measure of active suppression was correlated with a behavioral measure of trial-to-trial variations in the allocation of attention. Active suppression therefore appears to be a general-purpose mechanism that both prevents and terminates the allocation of attention.
ABSTRACT Fast radio bursts (FRBs) are newly discovered radio transient sources. Their high dispersion measures indicate an extragalactic origin. However, due to the lack of observational data in ...other wavelengths, their progenitors still remain unclear. Here we suggest that the collisions between neutron stars (NSs) and asteroids/comets are promising mechanisms for FRBs. During the impact process, a hot plasma fireball forms after the material of the small body penetrates into the NS surface. The ionized matter inside the fireball then expands along the magnetic field lines. Coherent radiation from the thin shell at the top of the fireball will account for the observed FRBs. Our scenario can reasonably explain the main features of FRBs, such as their durations, luminosities, and the event rate. We argue that for a single NS, FRBs are not likely to happen repeatedly in a forseeable timespan since such impacts are of low probability. We predict that faint remnant X-ray emissions should be associated with FRBs, but it may be too faint to be detected by detectors at work.
Decades of research in attention have shown that salient distractors (e.g., a color singleton) tend to capture attention. However, in most studies, singleton distractors are just as likely to be ...present as absent. We therefore have little knowledge of how probabilistic expectations of the salient distractor's occurrence and features affect suppression. In three experiments, we explored this question by manipulating the frequency of a singleton distractor and the variability of its color within a search display. We found that increased expectations regarding the occurrence of the singleton distractor eliminated the singleton response time cost and reduced the number of first saccades to the singleton. In contrast, expectations regarding variability in the singleton color did not affect singleton capture. This was surprising and suggests the ability to suppress second-order salience over and above that of first-order features. We next inserted the probe display that included a to-be-reported letter inside each shape between search trials to measure if attention went to multiple objects. The letter in the singleton location was reported less often in the high-frequency condition, suggesting proactive suppression of expected singleton. Additionally, we found that trial-to-trial repetitions of a singleton (irrespective of its color and location) facilitated performance (i.e., singleton repetition priming), but repetitions of its specific color or location did not. Together our findings demonstrate that attentional capture by a color singleton distractor is attenuated by probabilistic expectations of its occurrence, but not of its color and location.
Public Significance Statement
The mechanisms of target selection have been well-studied whereas those of distractor suppression are less well understood. One of reasons may be that there is still disagreement about whether salient distractors necessarily capture attention, which has led to a rich debate regarding the automaticity of attentional capture by stimulus saliency. However, these previous studies have primarily pitted attentional goals based on the target search strategy against perceptual saliency that cannot be predicted. We therefore have little knowledge of how probabilistic expectations affect attentional capture by a singleton distractor, yet performance in real-world environments rely heavily on expectations. We address this question in a series of three studies. Our results demonstrate that increased expectations regarding the occurrence of the singleton distractor eliminated attentional capture (indexed by search response time and first saccades). In contrast, expectations regarding singleton feature (i.e., color) did not affect singleton capture, even when there were 192 different singleton colors used. These results suggest that attentional capture by a singleton distractor is attenuated by probabilistic expectations of its occurrence, but not its specific color and location. This indicates that distractor suppression, like target selection, can operate at different levels of stimulus processing and be flexibly attuned to the type of information expected within the current environment.
Distractor Ignoring: Strategies, Learning, and Passive Filtering Geng, Joy J.; Won, Bo-Yeong; Carlisle, Nancy B.
Current directions in psychological science : a journal of the American Psychological Society,
12/2019, Letnik:
28, Številka:
6
Journal Article
Recenzirano
Odprti dostop
Our sensory environments contain more information than we can process, and successful behaviors require the ability to separate task-relevant information from task-irrelevant information. Much ...research on attention has focused on the mechanisms that result in selection of desired information, but much less is known about how distracting information is ignored. Here, we describe evidence that strategic, learned, and passive information can all contribute to better distractor ignoring. The evidence suggests that there are multiple ways in which distractor ignoring is supported, and these ways may be different from those of target selection. Future work will need to identify the mechanisms by which each source of information adjusts attentional priority such that irrelevant information is better ignored.
Background: Microparticles (MPs), small vesicles shed from stimulated cells, permit cross‐talk between cells within a particular environment. Their composition is thought to reflect their cell of ...origin, and differs according to whether they are produced by stimulation or by apoptosis. Whether MP properties vary according to stimulus is not yet known. Methods: We studied the characteristics of MPs produced from monocytic THP‐1 cells upon stimulation with lipopolysaccharide or a soluble P‐selectin chimera, using proteomics, flow cytometry, western blotting, and electron microscopy. Results: Utilizing a novel criterion of calcein‐AM staining to define MPs, we found that MP populations were similar with respect to size, presence and organization of cytoskeleton, and expression of certain antigens. The MPs shared the same level of procoagulant activity. We found that MPs also have distinct characteristics, depending on stimuli. These include differences in phosphatidylserine expression and expression of proteins from specific subcellular locations such as the mitochondria, and of unique antigens such as leukocyte‐associated immunoglobin‐like‐receptor (LAIR)‐1, which was found only upon stimulation with the soluble P‐selectin chimera. Conclusion: We found that the properties of MPs depend on the stimulus that produced them. This supports the concept that monocytic MPs differentially modulate thrombosis, inflammation and immune regulation according to stimulus.
The microstructure and tensile property of extruded Mg–1Ca–1Zn–0.6Zr alloy have been examined by means of electron backscattered diffraction, scanning and transmission electron microscopy. A fine ...microstructure and a typical basal texture are obtained in the extruded alloy which exhibits a yield strength as high as 306MPa along with a moderate elongation ~11%. The refined as-extruded microstructure is a result of the combination of dynamic recrystallisation and the Zener pinning effect induced by the fine precipitates. Both discontinuous and continuous dynamic recrystallisation are found to be operative in this study. Under tensile stress, cracks nucleate and propagate in the large Mg2Ca(Zn) particles which are formed during the solidification of casting and retained after extrusion.
The long-period stacking ordered structures 18R and 14H formed in Mg–Y–X (X=Zn, Cu, Ni) systems have received considerable interest over the past decade, but their thermal stability and relationships ...with other intermetallic phases in the Mg–Y–X systems remain to be unambiguously established. In this study, the occurrence and transformations of long-period stacking ordered structures 18R and 14H are clarified in as-cast and heat-treated Mg–Y–Zn alloys. The 18R structure is a stable equilibrium phase that forms directly from the melt whereas the 14H cannot form directly from the melt but forms in a solid-state transformation. That explains the absence of 14H in the as-cast microstructures of the alloys. These findings are embedded in the complete description of Mg–Y–Zn phase equilibria, generated by Calphad-type thermodynamic calculations and verified for a range of Mg-rich alloys by electron microscopy and thermal analysis. It is found that the 18R is a stable equilibrium phase that exists in the high temperature range from 753 to 483°C, and that the 14H is an equilibrium phase below 537°C. In the small temperature range between 537 and 483°C, the 18R and 14H can co-exist in equilibrium in some special alloy compositions.
Parietal cortex and attention Behrmann, Marlene; Geng, Joy J; Shomstein, Sarah
Current opinion in neurobiology,
April 2004, 2004-Apr, 2004-04-00, 20040401, Letnik:
14, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The parietal lobe forms about 20% of the human cerebral cortex and is divided into two major regions, the somatosensory cortex and the posterior parietal cortex. Posterior parietal cortex, located at ...the junction of multiple sensory regions, projects to several cortical and subcortical areas and is engaged in a host of cognitive operations. One such operation is selective attention, the process where by the input is filtered and a subset of the information is selected for preferential processing. Recent neuroimaging and neuropsychological studies have provided a more fine-grained understanding of the relationship between brain and behavior in the domain of selective attention.
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