Bottom-up Factor Research Articles

Investigating the influence of salience on distractor-response binding

ABSTRACT It is assumed that stimuli and their responses are integrated into an event file and that re-encounter with one or more integrated features leads to the retrieval of the event file. The Binding and Retrieval in Action Control framework (Frings et al., 2020) suggests that these integration and retrieval processes are independent and can be separately modulated by top-down and bottom-up factors. One suggested bottom-up factor is salience. Recent studies found evidence for the impact of salience on target-integration processes. In the present study, we merged two established paradigms, the additional singleton paradigm from visual search and the distractor-response binding paradigm, to investigate salient effects on distractors in action control. In two experiments, we observed standard distractor-response binding effects that, however, were not modulated by salience. We discuss these findings against recent theoriing from visual search arguing that salience becomes most effective with relevant features.

Does spatial variation in insect herbivory match variations in plant quality? A meta-analysis.

Variation in herbivore pressure has often been predicted from patterns in plant traits considered as antiherbivore defences. Here, we tested whether spatial variation in field insect herbivory is associated with the variation in plant quality by conducting a meta-analysis of 223 correlation coefficients between herbivory levels and the expression of selected plant traits. We found no overall correlation between herbivory and either concentrations of plant secondary metabolites or values of physical leaf traits. This result was due to both the large number of low correlations and the opposing directions of high correlations in individual studies. Field herbivory demonstrated a significant association only with nitrogen: herbivore pressure increased with an increase in nitrogen concentration in plant tissues. Thus, our meta-analysis does not support either theoretical prediction, i.e., that plants possess high antiherbivore defences in localities with high herbivore pressure or that herbivory is low in localities where plant defences are high. We conclude that information about putative plant defences is insufficient to predict plant losses to insects in field conditions and that the only bottom-up factor shaping spatial variation in insect herbivory is plant nutritive value. Our findings stress the need to improve a theory linking plant putative defences and herbivory.

Electrophysiological analysis of signal detection outcomes emphasizes the role of decisional factors in recognition memory.

Event-related potential (ERP) studies have identified two time windows associated with recognition memory and interpreted them as reflecting two processes: familiarity and recollection. However, using relatively simple stimuli and achieving high recognition rates, most studies focused on hits and correct rejections. This leaves out some information (misses and false alarms) that according to Signal Detection Theory (SDT) is necessary to understand signal processing. We used a difficult visual recognition task with colored pictures of different categories to obtain enough of the four possible SDT outcomes and analyzed them with modern ERP methods. Non-parametric analysis of these outcomes identified a single time window (470 to 670 ms) which reflected activity within fronto-central and posterior-left clusters of electrodes, indicating differential processing. The posterior-left cluster significantly distinguished all STD outcomes. The fronto-central cluster only distinguished ERPs according to the subject's response: yes vs. no. Additionally, only electrophysiological activity within the posterior-left cluster correlated with the discrimination index (d'). We show that when all SDT outcomes are examined, ERPs of recognition memory reflect a single-time window that may reveal a bottom-up factor discriminating the history of items (i.e. memory strength), as well as a top-down factor indicating participants' decision.

Visual adaptation changes the susceptibility to the fission illusion.

Sound-induced flash illusion (SiFI) is the illusion that participants perceive incorrectly that the number of visual flashes is equal to the number of auditory beeps when presented within 100 ms. Although previous studies found that repetition suppression can reduce an individual's perceptual sensitivity to the SiFI, there is not yet a consensus as to how visual adaptation affects the SiFI. In the present study, we added prolonged adapting visual stimuli prior to the presentation of audiovisual stimuli to investigate whether the bottom-up factor of adaptation affects the SiFI. The adapting visual stimuli consisted of one or two of the same visual stimuli that lasted for 2 minutes in succession, followed by the audiovisual stimuli. Both adaptation conditions showed SiFI effects. The accuracy of adapting double-flashes was significantly lower than that of in adapting a single flash for the fission illusion. Our analyses indicated that such a pattern could be attributed to a lower d' in adapting double-flashes than in adapting a single flash. However, the accuracy, discriminability and criterion were not significantly different between the two adaptation conditions because of the instability of the fusion illusion. Thus, the present study indicated that the reduced perceptual sensitivity based on visual adaptation could enhance the fission illusion in multisensory integration.

The mechanisms of selective attention in phenomenal consciousness

In three experiments we investigated the effects of selective attention in iconic memory and fragile-visual short-term memory (VSTM), which have been related to phenomenal consciousness. We used a novel retro-cue paradigm with different delays (early vs late) and object priorities (high vs equal vs low), to investigate (a) attentional costs and benefits and the role of (b) bottom-up factors and (c) fragile-VSTM in feature-based attentional selection. Experiment 1 showed that attentional costs modulate visual maintenance at longer delays, while Experiment 2 showed that by reducing the time exposure of the memory array from 250 ms to 100 ms, as a bottom-up factor, participants were not able to select the objects based on their priorities. Finally, Experiment 3 showed that a pattern mask presented before the transfer in visual working memory, attenuates the overall performance while preserving the priority effect. The implications for phenomenal consciousness before conscious access are discussed.

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Can the “10-year fishing ban” rescue biodiversity of the Yangtze River?

Integrating salience and action – Increased integration strength through salience

ABSTRACT It is assumed that stimuli and responses to them are integrated in an event file and further when all or some of these features repeat the previous event-file will be retrieved. The Binding and Retrieval in Action Control framework (Frings, C., Hommel, B., Koch, I., Rothermund, K., Dignath, D., Giesen, C., Kiesel, A., Kunde, W., Mayr, S., Moeller, B., Möller, M., Pfister, R., & Philipp, A. (2020). Binding and Retrieval in Action Control (BRAC). Trends in Cognitive Sciences, 24(5), 375–387. https://doi.org/10.1016/j.tics.2020.02.004 ) suggests that these integration and retrieval processes are independent, each can be individually modulated by top-down and bottom-up factors. One suggested bottom-up factor is salience. The present study investigated how target integration is modulated by salience in action control. Using a prime-probe design, targets were presented in either a salient colour or a non-salient colour in the prime. The results show that target-response binding is modulated by salience – integration is stronger when a target is presented in a salient colour compared to a non-salient colour. Salience modulates feature integration and thus the size of response binding effects.

Spatio-temporal variation in seed traits affects the occurrence and body-size pattern of a seed-feeding beetle (Chrysomelidae: Bruchinae) in Brazilian Cerrado

Seed quality is an important bottom-up factor driving life-history traits of seed beetles (Chrysomelidae: Bruchinae). However, information on how seed traits change spatiotemporally and affect herbivores' survival is incipient in Neotropics. We evaluated how the spatio-temporal variation in seed weight, hardness, size, and water content of Mimosa setosa var. paludosa (Fabaceae: Mimosoideae) affects the occurrence and body-size pattern of the seed beetle, Acanthoscelides quadridentatus (Schaeffer, 1907), in Brazilian Cerrado. We collected 400 fruits from four populations of M. setosa var. paludosa in Cerrado roadsides from Goiás and Minas Gerais states and then we assessed in laboratory seed traits along with the weight and body size of A. quadridentatus. Additionally, we collected a total of 76 fruits (immature plus mature) in beginning and end of the fruiting phase and counted the frequencies of unhatched and hatched eggs of the seed beetle to evaluate the effect of seed hardening on beetle posture. We found greater seed damage in the population with softer, smaller and lighter seeds. Larger and heavier seeds were harder than smaller and lighter seeds; and male and female reared from larger and heavier seeds were respectively 15 and 25% larger than that reared from smaller and lighter seeds. We also found that weight and body size of A. quadridentatus were positively correlated with seed length, weight and water content. Unhatched eggs were found only in beginning of fruiting phase when seeds were immature and softer, suggesting the occurrence of a window of time in which females lay their eggs before seed hardening to facilitate the entry of first instar larvae. These results highlight that larger and heavier seeds are most protected against herbivory, but individuals of A. quadridentatus that overcome plant hardness can grow larger in size. We suggest that seed traits change across a spatio-temporal scale and affect life-history traits of A. quadridentatus.

Disentangling bottom-up versus top-down and low-level versus high-level influences on eye movements over time.

Bottom-up and top-down as well as low-level and high-level factors influence where we fixate when viewing natural scenes. However, the importance of each of these factors and how they interact remains a matter of debate. Here, we disentangle these factors by analyzing their influence over time. For this purpose, we develop a saliency model that is based on the internal representation of a recent early spatial vision model to measure the low-level, bottom-up factor. To measure the influence of high-level, bottom-up features, we use a recent deep neural network-based saliency model. To account for top-down influences, we evaluate the models on two large data sets with different tasks: first, a memorization task and, second, a search task. Our results lend support to a separation of visual scene exploration into three phases: the first saccade, an initial guided exploration characterized by a gradual broadening of the fixation density, and a steady state that is reached after roughly 10 fixations. Saccade-target selection during the initial exploration and in the steady state is related to similar areas of interest, which are better predicted when including high-level features. In the search data set, fixation locations are determined predominantly by top-down processes. In contrast, the first fixation follows a different fixation density and contains a strong central fixation bias. Nonetheless, first fixations are guided strongly by image properties, and as early as 200 ms after image onset, fixations are better predicted by high-level information. We conclude that any low-level, bottom-up factors are mainly limited to the generation of the first saccade. All saccades are better explained when high-level features are considered, and later, this high-level, bottom-up control can be overruled by top-down influences.

Bridging the Gap: Adding Factors to Passive and Active Allocations

The authors examine how a factor allocation can be integrated into an asset owner’s existing roster of active managers. Using a risk-budgeting framework, they have several findings. (1) Asset owners who wish to maintain their existing roster of active managers and incorporate factor views may consider a top-down factor implementation, funded entirely from the core passive allocation. This approach distributed most of the active risk to active managers. (2) Asset owners who wish to preserve their existing roster of active managers and incorporate high-conviction factor views may consider an allocation between active management and a bottom-up factor implementation. This approach more evenly distributed the risk budget to active management and factors and partially funded the factor allocation from active management. (3) Asset owners who pursue a barbell strategy between core passive allocations and concentrated active managers could implement a low-volatility factor allocation, which may lower the total risk of the equity program, releasing active risk budget that can be deployed to active managers.

Top-down vs. bottom-up control on vegetation composition in a tidal marsh depends on scale

The relative impact of top-down control by herbivores and bottom-up control by environmental conditions on vegetation is a subject of debate in ecology. In this study, we hypothesize that top-down control by goose foraging and bottom-up control by sediment accretion on vegetation composition within an ecosystem can co-occur but operate at different spatial and temporal scales. We used a highly dynamic marsh system with a large population of the Greylag goose (Anser anser) to investigate the potential importance of spatial and temporal scales on these processes. At the local scale, Greylag geese grub for below-ground storage organs of the vegetation, thereby creating bare patches of a few square metres within the marsh vegetation. In our study, such activities by Greylag geese allowed them to exert top-down control by setting back vegetation succession. However, we found that the patches reverted back to the initial vegetation type within 12 years. At large spatial (i.e. several square kilometres) and temporal scales (i.e. decades), high rates of sediment accretion surpassing the rate of local sea-level rise were found to drive long-term vegetation succession and increased cover of several climax vegetation types. In summary, we conclude that the vegetation composition within this tidal marsh was primarily controlled by the bottom-up factor of sediment accretion, which operates at large spatial as well as temporal scales. Top-down control exerted by herbivores was found to be a secondary process and operated at much smaller spatial and temporal scales.

Galls in Schinus polygamus (Anacardiaceae): effects of forest structure on infestation intensity

Diverse ecological factors (top-down and bottom-up) act on the richness and abundance patterns of insect galls. Host plant density is a kind of bottom-up factor and is related to “resource concentration hypothesis.” In this study, we analyzed forest patches that differ in vegetational structure and host plant abundance: homogeneous forest patches (Schinus-dominated) and more complex forest patches, to determine whether there are differences in the intensity of gall infestation among individual trees. Insect galls were sampled from 15 Schinus polygamus trees along five transects in each forest (150 trees in total). Two galler species, a psyllid leaf galler and cecidomyiid shoot galler, were recorded. We found that Psyllidae gall infestation in S. polygamus presents higher values of galls per individual tree in Schinus-dominated forest patches than forest patches that are more diverse in plant species. Cecidomyiidae galls did not differ between areas and were not related to host plant abundance. We did not observe any variation in gall infestation within individual. Our study demonstrated that density-dependence effect could be more important for some galls species than others. The results suggest that biological attributes of galling insects’ infestation could be associated with susceptibility to host plant density.

Predator evasion in zooplankton is suppressed by polyunsaturated fatty acid limitation.

Herbivorous zooplankton avoid size-selective predation by vertical migration to a deep, cold water refuge. Adaptation to low temperatures in planktonic poikilotherms depends on essential dietary lipids; the availability of these lipids often limits growth and reproduction of zooplankton. We hypothesized that limitation by essential lipids may affect habitat preferences and predator avoidance behavior in planktonic poikilotherms. We used a liposome supplementation technique to enrich the green alga Scenedesmus obliquus and the cyanobacterium Synecchococcus elongatus with the essential lipids, cholesterol and eicosapentaenoic acid (EPA), and an indoor system with a stratified water-column (plankton organ) to test whether the absence of these selected dietary lipids constrains predator avoidance (habitat preferences) in four species of the key-stone pelagic freshwater grazer Daphnia. We found that the capability of avoiding fish predation through habitat shift to the deeper and colder environment was suppressed in Daphnia unless the diet was supplemented with EPA; however, the availability of cholesterol did not affect habitat preferences of the tested taxa. Thus, their ability to access a predator-free refuge and the outcome of predator-prey interactions depends upon food quality (i.e. the availability of an essential fatty acid). Our results suggest that biochemical food quality limitation, a bottom-up factor, may affect the top-down control of herbivorous zooplankton.

Exogenous features versus prior experiences modulate different subregions of the right IPL during episodic memory retrieval.

The fractionation view holds that distinct cognitive operations are mediated by subregions of the inferior parietal lobule (IPL). Within IPL, we hypothesised that retrieval-related activity in different parts of the right supramarginal gyrus (rSMG) may be modulated differentially by information acquired via different combinations of attention signals at encoding. We had two groups of participants watch a 42-min TV episode and, after a 24-hr delay, perform a temporal-order judgment task during fMRI. Each retrieval trial comprised three images presented sequentially, requiring participants to judge the temporal order between the first and last images while ignoring the second image (“distractor”). We manipulated the bottom-up factor by presenting distractors that were extracted from either an event-boundary or a non-boundary of the movie. The top-down factor was manipulated by instructing one group perform a segmentation task reporting the event-boundaries at encoding, while the other group watched the movie passively. Across groups, we found that the stimulus-related factor modulated retrieval activation in the anterior rSMG (areas PFt and PFop), whereas the goal-related influence of prior segmentation interacted with this effect in the middle rSMG (area PF), demonstrating IPL segregation during retrieval as a function of prior bottom-up vs. top-down attention signals.

A Novel Method of Visual Attention for Targets Detection

Inspired by the research of human visual system in neuroanatomy and psychology, the paper proposes a two-way collaborative visual attention model for target detection.In this new method , bottom-up attention information cooperates with top-down attention information to detect a target rapidly and accuractly. Firstly,the statistical prior knowledge of target and background is applied to optimize bottom-up attention information in different feature space and scale space.Secondly, after the SNR of salience difference between target and interference is computed ,the bottom-up gain factor is obtained.Thirdly, the gain factor is applied to adjust bottom up attention information extraction and then to maximize the salience contrast of target and background.Finally, target is detected by adjusted saliency.Experimental results shows that the proposed model in this paper can improve the real-time capability and reliability of target detection.

Light as a driver of phytoplankton growth and production in the freshwater tidal zone of a turbid estuary

Light is usually the main driver of phytoplankton growth in turbid estuaries, but it has received far less attention than nutrients as a bottom-up factor. This study presents the first experimental analysis of light limitation of phytoplankton growth and production and its seasonal variability in the freshwater tidal reaches of the turbid Guadiana estuary, SE Portugal/SW Spain. Natural phytoplankton communities were exposed to different photosynthetically active radiation (PAR) intensities. Short-term incubations with addition of 14HCO 3 − were used to estimate photosynthetic parameters and long-term incubations allowed the evaluation of the effects of light on phytoplankton composition and growth. Light limitation of phytoplankton growth occurred throughout the year in the freshwater tidal reaches of the estuary and no photoinhibition was observed at least up to 615 μmol photons m −2 s −1. In the summer, co-limitation by nutrients prevented a positive response of phytoplankton to light enrichment. Diatoms were the most light-limited group, whilst cyanobacteria were the only group acclimated to low-light conditions. Green algae and dinoflagellates responded positively to higher PAR exposures. High saturating irradiances, high light-saturated rates of primary production and low photosynthetic efficiencies suggest that phytoplankton community was not acclimated to the low-light conditions that prevail in the Guadiana estuary.

Emotional Processing in a Salient Motion Context: Integration of Motion and Emotion in Both V5/hMT+ and the Amygdala

Recent studies have suggested that the extent to which primary task demands draw on attentional resources determines whether or not task-irrelevant emotional stimuli are processed. Another important factor that can bias task-relevant and task-irrelevant stimulus competition is the bottom-up factor of stimulus salience. Here, we investigated the effect of stimulus salience associated with a primary motion task on the processing of emotional face distractors. Faces of different emotional valences were presented within a context of randomly moving dots. Subjects had to detect short intervals of coherent motion while ignoring the background faces. Task salience was manipulated by the level of motion coherence of the dots with high motion coherence being associated with high salience. Using functional magnetic resonance imaging, we show that emotional faces, compared with neutral faces, more strongly interfered with the primary task, as reflected in significant signal decreases in task-related motion area V5/hMT+. In addition, these faces elicited significant signal increases in the left amygdala. Most importantly, task salience was found to further increase amygdala's activity when presented together with an emotional face. Our data support a more general role of the amygdala as a behavioral relevance detector, which flexibly integrates behavioral relevant, salient context information to decode the emotional content of a visual scene.

Attentional guidance in singleton search: An examination of top-down, bottom-up, and intertrial factors

While it is clear that the goals of an observer change behaviour, their role in the guidance of visual attention has been much debated. In particular, there has been controversy over whether top-down knowledge can influence attentional guidance in search for a singleton item that is already salient by a bottom-up account (Theeuwes, Reimann, & Mortier, 2006). One suggestion is that passive intertrial priming accounts for what has been called top-down guidance (e.g., Maljkovic & Nakayama, 1994). In the present study, participants responded to the shape of a singleton target among homogenous distractors in a trial-by-trial cueing design. We examined the influence of target expectancy, trial history, and target salience (which was manipulated by changing the number of distractors). Top-down influence resulted in fast RTs that were independent of display size, even on trials that received no priming. Our findings show there is a role for top-down guidance, even in singleton search. The designation of intertrial priming as a bottom-up factor, rather than an implicit top-down factor (Wolfe, Butcher, Lee, & Hyle, 2003), is also discussed.

Stimulus similarity modulates competitive interactions in human visual cortex

When multiple visual stimuli are simultaneously presented in a neuron's receptive field, they often interact with each other by mutually suppressing their visually evoked responses, suggesting that multiple stimuli present at the same time in the visual field compete for neural representation. Previous research has shown that these suppressive interactions can be biased by top-down influences such as spatially directed attention, as well as by the bottom-up factor of visual salience. Using fMRI, we asked whether competitive interactions might also be modulated by other bottom-up factors and tested the effects of stimulus similarity. Specifically, we found that suppressive interactions in area V4, measured by comparing activity evoked by simultaneous (potentially competing) and sequential (noncompeting) presentations, were reduced when four items were identical relative to when the four items differed in color and orientation. Such a result is consistent with the prediction that competition is more likely to occur between groups than within a group.

GRAZERS, PRODUCER STOICHIOMETRY, AND THE LIGHT : NUTRIENT HYPOTHESIS REVISITED

The stoichiometric light:nutrient hypothesis (LNH) links the relative supplies of key resources with the nutrient content of tissues of producers. This resource-driven variation in producer stoichiometry, in turn, can mediate the efficiency of grazing. Typically, discussions of the LNH attribute this resource-stoichiometry link to bottom-up effects of light and phosphorus, which are mediated through producer physiology. Emphasis on bottom-up effects implies that grazers must consume food of quality solely determined by resource supply to ecosystems (i.e., they eat what they are served). Here, we expand upon this largely bottom-up interpretation with evidence from pond surveys, a mesocosm experiment, and a model. Data from shallow ponds showed the "LNH pattern" (positive correlation of an index of light : phosphorus supply with algal carbon : phosphorus content). However, algal carbon : phosphorus content also declined as zooplankton biomass increased in the ponds. The experiment and model confirmed that this latter correlation was partially caused by the various bottom-up and top-down roles of grazers: the LNH pattern emerged only in treatments with crustacean grazers, not those without them. Furthermore, model and experiment clarified that another bottom-up factor, natural covariation of nitrogen : phosphorus ratios with light : phosphorus supply (as seen in ponds), does not likely contribute to the LNH pattern. Finally, the experiment produced correlations between shifts in species composition of algae, partially driven by grazing effects of crustaceans, and algal stoichiometry. These shifts in species composition might shape stoichiometric response of producer assemblages to resource supply and grazing, but their consequences remain largely unexplored. Thus, this study accentuated the importance of grazing for the LNH; de-emphasized a potentially confounding, bottom-up factor (covarying nitrogen : phosphorus supply); and highlighted an avenue for future research for the LNH (grazer-mediated shifts in producer composition).