Top-down Bias Research Articles

Studying perceptual bias in favor of the from-above Necker cube perspective in a goal-directed behavior.

When viewing a completely ambiguous image, different interpretations can switch involuntarily due to internal top-down processing. In the case of the Necker cube, an entirely ambiguous stimulus, observers often display a bias in perceptual switching between two interpretations based on their perspectives: one with a from-above perspective (FA) and the other with a from-below perspective (FB). Typically, observers exhibit a priori top-down bias in favor of the FA interpretation, which may stem from a statistical tendency in everyday life where we more frequently observe objects from above. However, it remains unclear whether this perceptual bias persists when individuals voluntarily decide on the Necker cube's interpretation in goal-directed behavior, and the impact of ambiguity in this context is not well-understood. In our study, we instructed observers to voluntarily identify the orientation of a Necker cube while manipulating its ambiguity from low (LA) to high (HA). Our investigation aimed to test two hypotheses: (i) whether the perspective (FA or FB) would result in a bias in response time, and (ii) whether this bias would depend on the level of stimulus ambiguity. Additionally, we analyzed electroencephalogram (EEG) signals to identify potential biomarkers that could explain the observed perceptual bias. The behavioral results confirmed a perceptual bias in favor of the from-above perspective, as indicated by shorter response times. However, this bias diminished for stimuli with high ambiguity. For the LA stimuli, the occipital theta-band power consistently exceeded the frontal theta-band power throughout most of the decision-making time. In contrast, for the HA stimuli, the frontal theta-band power started to exceed the occipital theta-band power during the 0.3-s period preceding the decision. We propose that occipital theta-band power reflects evidence accumulation, while frontal theta-band power reflects its evaluation and decision-making processes. For the FB perspective, occipital theta-band power exhibited higher values and dominated over a longer duration, leading to an overall increase in response time. These results suggest that more information and more time are needed to encode stimuli with a FB perspective, as this template is less common for the observers compared to the template for a cube with a FA perspective.

“Sponge Maps”: Using the Concept of Value by Area Maps for Avoiding the Area Size Bias in Choropleth Maps

A well-known problem with choropleth maps is the cognitively induced effect that larger regions are perceived as more dominant. Consequently, unsatisfactory detection rates for small areas can result, which becomes relevant when important spatial features or patterns are explored (e.g., regions with maximum values). One possible approach to avoiding the area size bias is the use of cartograms. While there is already some work on Equal Are Unit Maps, little or no research has been done on the possibility of applying the concept of Value By Area Maps to transform the reference area maps. One goal of this article is to introduce the concept of so-called “Sponge Maps”, which distort the base maps independently of thematic attributes, but depending on the need to show or emphasize certain areas of interest. The second goal of the article is to answer the overall research question whether Sponge Maps actually reduce the area size bias and improve the detectability of maximum value regions. A user study was able to verify the effectiveness of the Sponge Map approach in particular. However, it also became clear that not only the area size bias plays a role in the detection of important regions—dependencies on the absolute position (top-down bias), compactness or conspicuous shape (shape bias), the familiarity (awareness bias), the color intensity (darkness bias) and not least by the distortions in the Sponge Maps as such (distortion bias) are shown. Furthermore, special aspects of detecting minimum value regions are revealed (including the so-called inverse area size bias).

Cognitive flexibility in post-traumatic stress disorder: Sustained interference associated with altered modulation of cortical oscillatory activity during task-switching

Post-traumatic stress disorder (PTSD) is associated with deficits in cognitive flexibility, with evidence suggesting that these deficits may be a risk factor for the development of core PTSD symptoms. Understanding the neurophysiological substrate of this association could aid the development of effective therapies for PTSD. In this study, we investigated the relationship between post-traumatic stress severity (PTSS) in service members with combat exposure and the modulation of cortical oscillatory activity during a test of cognitive flexibility. Participants were assigned to three groups based on PTSS scores: low (well below a threshold consistent with a diagnosis of PTSD, n = 30), moderate (n = 32), and high (n = 29) symptom severity. Magnetoencephalography data were recorded while participants performed a cued rule-switching task in which two matching rules were repeated or switched across consecutive trials. Participants with high PTSS had longer reaction times for both switch and repeat trials, and showed evidence of sustained residual interference during repeat trials. During the cue-stimulus interval, participants with moderate and high PTSS showed higher relative theta power in switch trials over left dorsolateral prefrontal cortex (DLPFC). After test-stimulus onset, participants with high PTSS showed less suppression of beta band activity, which was present over multiple prefrontal, parietal, and temporal regions in switch trials, but it was confined to ventromedial prefrontal cortex in repeat trials. Higher theta band activity is a marker of effortful voluntary shifting of attention, while lower suppression of beta band activity reflects difficulties with inhibition of competing perceptual information and courses of action. These findings are consistent with a role for altered suppression of beta band activity, which can be due to less effective top-down bias signals exerted by DLPFC, in the etiology of cognitive flexibility deficits in PTSD.

Top-down threat bias in pain perception is predicted by intrinsic structural and functional connections of the brain

Top-down processes such as expectations play a key role in pain perception. In specific contexts, inferred threat of impending pain can affect perceived pain more than the noxious intensity. This biasing effect of top-down threats can affect some individuals more strongly than others due to differences in fear of pain. The specific characteristics of intrinsic brain characteristics that mediate the effects of top-down threat bias are mainly unknown. In this study, we examined whether threat bias is associated with structural and functional brain connectivity. The variability in the top-down bias was mapped to the microstructure of white matter in diffusion weighted images (DWI) using MRTrix3. Mean functional connectivity of five canonical resting state networks was tested for association with bias scores and with the identified DWI metrics. We found that the fiber density of the splenium of the corpus callosum was significantly low in individuals with high top-down threat bias (FWE corrected with 5000 permutations, p < 0.05). The mean functional connectivity within the language/memory and between language/memory and default mode networks predicted the bias scores. Functional connectivity within language memory networks predicted the splenium fiber density, higher pain catastrophizing and lower mindful awareness. Probabilistic tractography showed that the identified region in the splenium connected several sensory regions and high-order parietal regions between the two hemispheres, indicating the splenium's role in sensory integration. These findings demonstrate that individuals who show more change in pain with changes in the threat of receiving a stronger noxious stimulus have lower structural connectivity in the pathway necessary for integrating top-down cue information with bottom-up sensory information. Conversely, systems involved in memory recall, semantic and self-referential processing are more strongly connected in people with top-down threat bias.

The role of alpha oscillations in temporal binding within and across the senses.

An intriguing notion in cognitive neuroscience posits that alpha oscillations mould how the brain parses the constant influx of sensory signals into discrete perceptual events. Yet, the evidence is controversial and the underlying neural mechanism unclear. Further, it is unknown whether alpha oscillations influence observers’ perceptual sensitivity (i.e. temporal resolution) or their top-down biases to bind signals within and across the senses. Combining EEG, psychophysics and signal detection theory, this multi-day study rigorously assessed the impact of alpha frequency on temporal binding of signals within and across the senses. In a series of two-flash discrimination experiments twenty human observers were presented with one or two flashes together with none, one or two sounds. Our results provide robust evidence that pre-stimulus alpha frequency as a dynamic neural state and an individual’s trait index does not influence observers’ perceptual sensitivity or bias for two-flash discrimination in any of the three sensory contexts. These results challenge the notion that alpha oscillations have a profound impact on how observers parse sensory inputs into discrete perceptual events.

Reward-driven modulation of spatial attention in the human frontal eye-field

Attentional selection and the decision of where to make an eye-movement are driven by various factors such as the representation of salience, task goal, and stimulus relevance, as well as expectations or predictions based on past experience. Brain systems implicated in these processes recruit cortico-subcortical areas including the Frontal Eye-Field (FEF), parietal cortex, or superior colliculus. How these areas interact to govern attention remains elusive. Priority maps of space have been observed in several brain regions, but the neural substrates where different sources of information are combined and integrated to guide attentional selection has not been elucidated. We investigated here the neural mechanisms subserving how reward cues influence the voluntary deployment of attention, in conditions where stimulus-driven capture and task-related goals compete for attention selection. Using fMRI in a visual search task in n = 23 participants, we found a selective modulation of FEF by the reward value of distractors during attentional shifts, particularly after high-predictive cueing to invalid locations. Reward information also modulated FEF connectivity to superior colliculus, striatum, and visual cortex. We conclude that FEF may occupy a central position within brain circuits integrating different sources of top-down biases for the generation of spatial saliency maps and guidance of selective attention.

The role of contingency and correlation in the Stroop task.

Facilitation (faster responses to Congruent trials compared with Neutral trials) in the Stroop task has been a difficult effect for models of cognitive control to explain. The current research investigated the role of word-response contingency, word-colour correlation, and proportion congruency in producing Stroop effects. Contingency and correlation refers to the probability of specific word-response and word-colour pairings that are implicitly learnt while performing the task. Pairs that have a higher probability of occurring are responded to faster, a finding that challenges top-down attention control accounts of Stroop task performance. However, studies that try to experimentally control for contingency and correlation typically do so by increasing the proportion of incongruent trials in the task, which cognitive control accounts posit affects interference control via the top-down biasing of attention. The present research focused on whether facilitation is also affected by contingency and correlation while additionally looking at the effect of proportion congruency. This was done in two experiments that compared the typical design of Stroop task experiments (i.e., having equal proportions of Congruent and Incongruent trials but also contingency and correlational biases) to: (a) a design that had unequal congruency proportions but no contingency or correlation bias (Experiment 1) and (b) a design where the correlation is biased but proportion congruency and contingency were not (Experiment 2). Results did not support the hypotheses that contingency or correlation affected facilitation. However, interference was almost halved in the alternative design of Experiment 2, demonstrating an effect of contingency learning in typical measures of Stroop interference.

Theeuwes, J., &amp; Failing, M. Attentional Selection: Top-Down, Bottom-Up and History-Based Biases

Theeuwes, J., &amp; Failing, M. <i>Attentional Selection: Top-Down, Bottom-Up and History-Based Biases</i>

Top-down control of attention under varying task loads

The performance of a goal-directed task is often interrupted by task-irrelevant distractors. This distractor interference has well been demonstrated in a large body of studies employing the Eriksen flanker paradigm. A notable finding regarding this issue is that distractor interference is attenuated by increased perceptual load or the presence of non-target stimuli diluting distractors. Besides increased perceptual load or the presence of diluters, we hypothesized that either suppression of distractor or enhancement of target via top-down attentional control would also contribute to modulating distractor interference. To test this, we had participants identify a target stimulus while ignoring a distractor under three different conditions; under low load, only the target and distractor was presented, while under high load, the target was surrounded by non-target letters. In the dilution condition, the target was accompanied by non-targets, whose colors were distinct from the target. Importantly, following the task stimuli, a probe stimulus was presented either in the target location, non-target location, or distractor location. As results, under low load, attention was captured by the target stimulus in a bottom-up manner at the early stage of processing. By contrast, in the high load and dilution conditions, attention was focused on the target in a top-down manner. Taken together, we suggest that increasing perceptual load or presenting diluters incentivizes the establishment of top-down bias toward the target stimulus, which plays a role in attenuating distractor interference.

Numbers in short-term memory bias auditory spatial perception.

The cognitive penetration literature suggests that top-down knowledge influences perception, but whether such influences exist is controversial. We tested for top-down influences on perception by loading short-term memory with digits and then had participants make perceptual judgments to index spatial hearing. Memory of spatial number codes were predicted to bias spatial judgments to the left for small digits and rightward for larger digits. Participants encoded one or more digits and then made spatial judgments in either spatial hearing or dichotic listening tasks. Results across five experiments supported the predicted spatial biases. Digits had to be deliberately encoded, and at least two were needed to be memorized before a small number left-right bias in dichotic listening was evident. In dichotic listening, smaller numbers in memory also promoted more intrusions, and a mix of small and large numbers enhanced the right ear advantage. Results suggest that long-term knowledge about number magnitude imparts a top-down bias on auditory spatial perception. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Short-term Focused Attention Meditation Restricts the Retrieval of Stimulus-Response Bindings to Relevant Information

ObjectivesGoal-direct actions require integrating processing of stimuli and responses, which is why close stimulus-response bindings have to be created. However, the strength of these bindings can be modified. The metacontrol state model (MSM) hypothesizes that this can be achieved through mindfulness meditation. Yet, the cognitive processes underlying possible effects of meditation on S-R bindings remain unexplored.MethodsWe examined the effects of a brief bout of focused attention (FA) meditation on S-R bindings using a standard event file task measuring S-R bindings. This was done in a within-subject (crossover) design, where each participant (novice to meditation) was examined at two separate appointments (with and without meditation before the task).ResultsWe found that 15 min of a single bout of FA meditation was enough to restrict the retrieval of S-R bindings to relevant information as indexed by decreased partial overlap costs.ConclusionThese findings support the MSM framework suggesting that FA meditation induces a top-down biasing of processes toward cognitive persistence. Importantly, however, the effects of FA meditation were only evident when there was prior experience with the task. This shows close similarities to effects in pharmacological and brain stimulation studies and suggests that FA meditation modulates gain control principles in information processing. Moreover, effects of FA meditation were restricted in its duration since FA meditation modulated the retrieval of S-R bindings only in the early phases of the event file task. In novices, effects of short-term FA meditation are thus relatively fragile and only induce some finer adjustments in processing strategy.

Complementary interactions between classical and top-down driven inhibitory mechanisms of attention

Selective attention informs decision-making by biasing perceptual processing towards task-relevant stimuli. In experimental and computational literature, this is most often implemented through top-down excitation of selected stimuli. However, physiological and anatomical evidence shows that in certain situations, top-down signals could instead be inhibitory. In this study, we investigated how such an inhibitory mechanism of top-down attention compares with an excitatory one. We did so in a neurorobotics context where the agent was controlled using an established hierarchical architecture. We augmented the architecture with an attentional system that implemented top-down attention biasing as connection gains. We tested four models of top-down attention on the simulated agent performing a foraging task: without top-down biasing, with only excitatory top-down gain, with only inhibitory top-down gain, and with both excitatory and inhibitory top-down gain. We manipulated the reward-distractor ratio that was presented and assessed the agent's performance using accumulated rewards and the latency of the selection. Using these measures, we provide evidence that excitatory and inhibitory mechanisms of attention complement each other.

The attentional blink: A relational accountof attentional engagement.

Visual attention allows selecting relevant information from cluttered visual scenes and is largely determined by our ability to tune or bias visual attention to goal-relevant objects. Originally, it was believed that this top-down bias operates on the specific feature values of objects (e.g., tuning attention to orange). However, subsequent studies showed that attention is tuned to in a context-dependent manner to the relative feature of a sought-after object (e.g., the reddest or yellowest item), which drives covert attention and eye movements in visual search. However, the evidence for the corresponding relational account is still limited to the orienting of spatial attention. The present study tested whether the relational account can be extended to explain attentional engagement and specifically, the attentional blink (AB) in a rapid serial visual presentation (RSVP) task. In two blocked conditions, observers had to identify an orange target letter that could be either redder or yellower than the other letters in the stream. In line with previous work, a target-matching (orange) distractor presented prior to the target produced a robust AB. Extending on prior work, we found an equally large AB in response to relatively matching distractors that matched only the relative color of the target (i.e., red or yellow; depending on whether the target was redder or yellower). Unrelated distractors mostly failed to produce a significant AB. These results closely match previous findings assessing spatial attention and show that the relational account can be extended to attentional engagement and selection of continuously attended objects in time.

The role of the left dorsolateral prefrontal cortex in attentional bias

The DLPFC is thought to be critically involved in maintaining attention away from behaviourally irrelevant information, and in the establishment of attentional control settings. These play an important role in the phenomenon of top-down bias to features in the visual field – also known as attentional bias. This paper probes the involvement of the left DLPFC in attentional bias by manipulating its cortical excitability via tDCS and then analysing these effects following an induced attentional bias towards the colour green. Although both anodal and cathodal tDCS over the left DLPFC decrease distractibility caused by biased but irrelevant objects, further interrogation of our data reveals theoretically differential mechanisms for each type of stimulation. Anodal tDCS appears to increase cognitive control over attentional bias-related items that are behaviourally irrelevant, allowing for their efficient disregard. In contrast, cathodal tDCS appears to lessen the overall effect of the induced attentional bias, potentially by reducing the influence of top-down modulated attentional control settings thus preventing the implementation of the control setting favouring green items. These results suggest a potential causal role of the left DLPFC in the cognitive mechanism underlying attentional bias.

Plasticity in brain activity dynamics after task-shifting training in older adults

Cognitive control is supported by a dynamic interplay of transient (i.e., trial-related) brain activation across fronto-parietal networks and sustained (i.e., block-related) activation across fronto-striatal networks. Older adults show disturbances in this dynamic functional recruitment. There is evidence suggesting that cognitive-control training may enable older adults to redistribute their brain activation across cortical and subcortical networks, which in turn can limit behavioral impairments. However, previous studies have only focused on spatial rather than on temporal aspects of changes in brain activation. In the present study, we examined training-related functional plasticity in old age by applying a hybrid fMRI design that sensitively tracks the spatio-temporal interactions underlying brain-activation changes. Fifty healthy seniors were assigned to a task-shifting training or an active-control group and their pretest/posttest activation-change maps were compared against 25 untrained younger adults. After training, older adults showed the same performance as untrained young adults. Compared to the control group, task-shifting training promoted proactive (i.e., early, cue-related) changes in transient mechanisms supporting the maintenance and top-down biasing of task-set representations in a specific prefrontal circuitry; reactive (i.e., late, probe-related) changes in transient mechanisms supporting response-selection processes in dissociable fronto-parietal networks; overall reductions of sustained activation in striatal circuits. Results highlight the importance of spatio-temporal interactions in training-induced neural changes in age.

Rhythmic Temporal Expectation Boosts Neural Activity by Increasing Neural Gain.

Temporal orienting improves sensory processing, akin to other top-down biases. However, it is unknown whether these improvements reflect increased neural gain to any stimuli presented at expected time points, or specific tuning to task-relevant stimulus aspects. Furthermore, while other top-down biases are selective, the extent of trade-offs across time is less well characterized. Here, we tested whether gain and/or tuning of auditory frequency processing in humans is modulated by rhythmic temporal expectations, and whether these modulations are specific to time points relevant for task performance. Healthy participants (N = 23) of either sex performed an auditory discrimination task while their brain activity was measured using magnetoencephalography/electroencephalography (M/EEG). Acoustic stimulation consisted of sequences of brief distractors interspersed with targets, presented in a rhythmic or jittered way. Target rhythmicity not only improved behavioral discrimination accuracy and M/EEG-based decoding of targets, but also of irrelevant distractors preceding these targets. To explain this finding in terms of increased sensitivity and/or sharpened tuning to auditory frequency, we estimated tuning curves based on M/EEG decoding results, with separate parameters describing gain and sharpness. The effect of rhythmic expectation on distractor decoding was linked to gain increase only, suggesting increased neural sensitivity to any stimuli presented at relevant time points.SIGNIFICANCE STATEMENT Being able to predict when an event may happen can improve perception and action related to this event, likely due to the alignment of neural activity to the temporal structure of stimulus streams. However, it is unclear whether rhythmic increases in neural sensitivity are specific to task-relevant targets, and whether they competitively impair stimulus processing at unexpected time points. By combining magnetoencephalography and encephalographic recordings, neural decoding of auditory stimulus features, and modeling, we found that rhythmic expectation improved neural decoding of both relevant targets and irrelevant distractors presented and expected time points, but did not competitively impair stimulus processing at unexpected time points. Using a quantitative model, these results were linked to nonspecific neural gain increases due to rhythmic expectation.

Dynamics of auditory spatial attention gradients

Auditory spatial attention faces the conflicting demands of focusing on the current task while also rapidly shifting location to unexpected stimuli. We examined the interplay of sustained focus and intermittent shifts in an auditory spatial attention task. Most trials required a choice response from a standard location in virtual space (L-R: −90°, 0°, +90°), but occasionally the location shifted between 45°-180°. Reaction time curves for angular shifts had a quadratic shape, with slowing for small shifts but faster reaction times for larger shifts. The reaction time curves were maintained at faster stimulus rates and usually scaled to fit the range of stimulus locations. However, focus on the right had an attenuated curve, and did not scale to the range of locations. The findings suggest two mechanisms: a top-down bias centered on standard locations that decreases with distance, and a bottom-up bias that under these conditions increases with distance from the standard location.

Analysis of Biased Competition and Cooperation for Attention in the Cerebral Cortex.

A new approach to understanding the interaction between cortical areas is provided by a mathematical analysis of biased competition, which describes many interactions between cortical areas, including those involved in top-down attention. The analysis helps to elucidate the principles of operation of such cortical systems, and in particular the parameter values within which biased competition operates. The analytic results are supported by simulations that illustrate the operation of the system with parameters selected from the analysis. The findings provide a detailed mathematical analysis of the operation of these neural systems with nodes connected by feedforward (bottom-up) and feedback (top-down) connections. The analysis provides the critical value of the top-down attentional bias that enables biased competition to operate for a range of input values to the network, and derives this as a function of all the parameters in the model. The critical value of the top-down bias depends linearly on the value of the other inputs, but the coefficients in the function reveal non-linear relations between the remaining parameters. The results provide reasons why the backprojections should not be very much weaker than the forward connections between two cortical areas. The major advantage of the analytical approach is that it discloses relations between all the parameters of the model.

Learning What Is Irrelevant or Relevant: Expectations Facilitate Distractor Inhibition and Target Facilitation through Distinct Neural Mechanisms.

It is well known that attention can facilitate performance by top-down biasing processing of task-relevant information in advance. Recent findings from behavioral studies suggest that distractor inhibition is not under similar direct control but strongly dependent on expectations derived from previous experience. Yet, how expectations about distracting information influence distractor inhibition at the neural level remains unclear. The current study addressed this outstanding question in three experiments in which search displays with repeating distractor or target locations across trials allowed human observers (male and female) to learn which location to selectively suppress or boost. Behavioral findings demonstrated that both distractor and target location learning resulted in more efficient search, as indexed by faster response times. Crucially, distractor learning benefits were observed without target location foreknowledge, unaffected by the number of possible target locations, and could not be explained by priming alone. To determine how distractor location expectations facilitated performance, we applied a spatial encoding model to EEG data to reconstruct activity in neural populations tuned to distractor or target locations. Target location learning increased neural tuning to target locations in advance, indicative of preparatory biasing. This sensitivity increased after target presentation. By contrast, distractor expectations did not change preparatory spatial tuning. Instead, distractor expectations reduced distractor-specific processing, as reflected in the disappearance of the Pd event-related potential component, a neural marker of distractor inhibition, and decreased decoding accuracy. These findings suggest that the brain may no longer process expected distractors as distractors, once it has learned they can safely be ignored.SIGNIFICANCE STATEMENT We constantly try hard to ignore conspicuous events that distract us from our current goals. Surprisingly, and in contrast to dominant attention theories, ignoring distracting, but irrelevant, events does not seem to be as flexible as is focusing our attention on those same aspects. Instead, distractor suppression appears to strongly rely on learned, context-dependent expectations. Here, we investigated how learning about upcoming distractors changes distractor processing and directly contrasted the underlying neural dynamics to target learning. We show that, while target learning enhanced anticipatory sensory tuning, distractor learning only modulated reactive suppressive processing. These results suggest that expected distractors may no longer be considered distractors by the brain once it has learned that they can safely be ignored.

Error-preceding brain activity links neural markers of task preparation to cognitive stability and flexibility

Balancing stability and flexibility is required to facilitate successful task selection in situations with competing stimuli. Research suggests a set of counteracting control processes that maintains this balance. In the present study, we investigate how two neural correlates of task preparation in event-related potentials (ERPs), the mixing positivity and the switch positivity, can be linked to stability and flexibility in task selection. In a cued task switching paradigm, we analyzed deviations of these ERPs when task confusions occurred, that is, when participants erroneously executed the currently irrelevant task. We found a reduced mixing positivity to be a main source of task confusions in a task environment that required ongoing switches between competing tasks, whereas the switch positivity was uninvolved here. However, an overabundance of this latter component was a source of task confusions in a task environment that required the repetitive execution of the same task, although task switches were not required at all in this condition. These results not only highlight the distinct functional significance of the two preparatory ERPs and show that control processes can be maladaptive in certain contexts. They can also be utilized to locate the mixing positivity and the switch positivity on the stability-flexibility spectrum. Our results are in line with accounts that suggest that a balance between stability and flexibility is facilitated by the concurrent involvement of two control processes. One that manages the top-down bias of the relevant task set and one that increases or decreases competition between alternatively available stimuli.