Attentional capture and inhibition (of return): the effect on perceptual sensitivity

Different gain modulations of selective attention at short and long cue-target delays

Previous studies have tested attentional gain patterns, for example, within the normalization model of attention (NMoA), by altering the relative sizes of the attention field and stimuli. Existing studies have not investigated whether the gain patterns of altering the relative exogenous cue size as compared with the target stimuli matches the prediction of NMoA and whether these gain patterns exist in the late stage of attentional processing. To resolve these questions, the present study maintained the target grating size and changed the exogenous cue size in both short and long cue-target onset asynchronies (CTOAs) conditions. The results revealed response gain for small cue/large target size conditions and contrast gain for large cue/small target size conditions, which was consistent with the NMoA. However, we observed the decrease in the contrast gain factor only with long CTOAs, regardless of whether the cue size was relatively small or large. This indicated that NMoA-related effects based on the relative attentional field dominated in the early stage and that the contrast gain dominated in the late stage.

Statistical distractor learning modulates perceptual sensitivity

The present study used perceptual sensitivity (d′) to determine the spatial distribution of attention in displays in which participants have learned to suppress a location that is most likely to contain a distractor. Participants had to indicate whether a horizontal or a vertical line, which was shown only briefly before it was masked, was present within a target shape. Critically, the target shape could be accompanied by a singleton distractor color, which when present appeared with a high probability at one display location. The results show that perceptual sensitivity was reduced for locations likely to contain a distractor, as d′ was lower for this location than for all other locations in the display. We also found that the presence of an irrelevant color singleton reduced the gain for input at the target location, particularly when the irrelevant singleton was close to the target singleton. We conclude that, through the repeated encounter with a distractor at a particular location, the weights within the attentional priority map are changed such that the perceptual sensitivity for objects presented at that location is reduced relative to all other locations. This reduction of perceptual sensitivity signifies that this location competes less for attention than all other locations.

Numerosity adaptation partly depends on the allocation of implicit numerosity-contingent visuo-spatial attention

Like other perceptual attributes, numerosity is susceptible to adaptation. Nevertheless, it has never been fully investigated whether adaptation to numerosity is fully perceptual in nature or if it stems from the mixed influence of perception and attention. In the present work, we addressed this point throughout three separate experiments aiming at investigating the potential role played by visuo-spatial attentional mechanisms in shaping numerosity perception and adaptation. In Experiments 1 and 2, we showed that the magnitude of numerosity adaptation can be strongly influenced by the distribution of numerosity-contingent visuo-spatial attentional resources during the adaptation period. Results from Experiment 1 revealed a robust reduction of adaptation magnitude whenever a second numerical stimulus was presented in a diametrically opposite location from that of the adaptor, despite this second adapter being neutral as matched in numerosity with the following stimulus displayed in that location. In Experiment 2, we showed that this reduction in adaptation did not occur in cases where the second stimulus was not numerical, suggesting that attentional resources specifically related to numerosity information accounts for the results of Experiment 1. Finally, in Experiment 3, we showed that uninformative visuo-spatial cues shape numerosity discrimination judgments both at baseline and during adaptation. Taken together, our results seem to indicate that visuo-spatial attention plays a relevant role in numerosity perception and that adaptation to numerosity is actively influenced by this cognitive process.

Reduction of emotional distraction during target processing by attentional manipulations

Previous research has demonstrated that fully irrelevant distractors - i.e., not sharing any feature with the target - capture our attention and modulate our responses. In the present study, we explored this interference by irrelevant distractors in a series of three experiments wherein the emotional valence of distractors (negative vs. neutral valence) was manipulated along with endogenous and exogenous attention. We aimed at jointly investigating - within the same paradigm - the possible modulations over the interference effect by these three critical variables in a systematic way. Although we replicated the interference effect by distractors previously reported in Martín-Arévalo et al. (2015), results showed no attentional and only weak emotional valence modulations over the interference effect. We discuss the possible boundary conditions underlying the absence (or weakness) of modulations over the interference effect by distractors observed in our experiments.

Mindfulness and Attention: Current State-of-Affairs and Future Considerations

This review examines longitudinal studies of changes in components of attention following mindfulness training. A total of 57 retreat studies, non-randomized trials, and randomized controlled trials were identified. Employing the classical taxonomy proposed by Posner and Petersen (1990), outcome measures were broadly categorized based on whether they involved maintenance of an aroused state (alerting), selective prioritization of attention to target items (orienting), or assessed conflict monitoring (executive attention). Although many non-randomized and retreat studies provide promising evidence of gains in both alerting and conflict monitoring following mindfulness training, evidence from randomized controlled trials, especially those involving active control comparison groups, is more mixed. This review calls attention to the urgent need in our field of contemplative sciences to adopt the methodological rigor necessary for establishing mindfulness meditation as an effective cognitive rehabilitation tool. Although studies including wait-listed control comparisons were fruitful in providing initial feasibility data and pre-post effect sizes, there is a pressing need to employ standards that have been heavily advocated for in the broader cognitive and physical training literatures. Critically, inclusion of active comparison groups and explicit attention to the reduction of demand characteristics are needed to disentangle the effects of placebo from treatment. Further, detailed protocols for mindfulness and control groups and examination of theoretically guided outcome variables with established metrics for reliability and validity are key ingredients in the systematic study of mindfulness meditation. Adoption of such methodological rigor will allow for causal claims supporting mindfulness training as an efficacious treatment modality for cognitive rehabilitation and enhancement.

Automatic and controlled attentional capture by threatening stimuli

The rapid orienting of attention to potential threats would seem to proceed outside of top-down control. However, there is no convincing empirical finding that threatening stimuli only capture attention in a bottom-up way. The present study was designed to investigate the role of top-down and bottom-up processes in attentional bias to threats. We report a dot-probe experiment examining spatial cuing (valid and invalid) using threatening (spiders or snakes) or neutral (clownfish) stimuli in two conditions (predictable and unpredictable task). Forty-two students between the ages of 20 and 35 years participated in the study. They performed the probe detection task. Results suggested that threatening stimuli can capture attention, but this attentional effect cannot be regarded as totally bottom-up or automatic. We argue that attentional capture by threatening stimuli could be the result of a mechanism of attention shifting between bottom-up and top-down systems.

Visual Selection: Usually Fast and Automatic; Seldom Slow and Volitional

Recently it was argued that in addition to top-down and bottom-up processes, lingering biases of selection history play a major role in visual selection (Awh, Belopolsky & Theeuwes, 2012). Since its publication there has been a growing controversy about the terms top-down, bottom-up and selection-history in relation to visual selection. In the current paper we define these terms, discuss some controversies about these terms and explain what kind of effects should be considered to be the result of lingering biases of selection history, i.e., priming, reward/fear, and statistical learning. We discuss the properties of top-down selection (slow, effortful, and controlled) versus the properties of lingering biases of selection history (fast, effortless, and automatic). We adhere the position that the experience with selecting a particular feature or the location of a feature, may boost and sharpen its representation within the priority selection map above and beyond its physical salience. It is as if the experience may render a feature or location subjectively more salient. Our message of the current review is that true top-down control of visual selection occurs far less often than what is typically assumed. Most of the time, selection is based on experience and history. It is fast, automatic and occurs without much, if any, effort.

Feature singletons attract spatial attention independently of feature priming

People perform better in visual search when the target feature repeats across trials (intertrial feature priming [IFP]). Here, we investigated whether repetition of a feature singleton's color modulates stimulus-driven shifts of spatial attention by presenting a probe stimulus immediately after each singleton display. The task alternated every two trials between a probe discrimination task and a singleton search task. We measured both stimulus-driven spatial attention (via the distance between the probe and singleton) and IFP (via repetition of the singleton's color). Color repetition facilitated search performance (IFP effect) when the set size was small. When the probe appeared at the singleton's location, performance was better than at the opposite location (stimulus-driven attention effect). The magnitude of this attention effect increased with the singleton's set size (which increases its saliency) but did not depend on whether the singleton's color repeated across trials, even when the previous singleton had been attended as a search target. Thus, our findings show that repetition of a salient singleton's color affects performance when the singleton is task relevant and voluntarily attended (as in search trials). However, color repetition does not affect performance when the singleton becomes irrelevant to the current task, even though the singleton does capture attention (as in probe trials). Therefore, color repetition per se does not make a singleton more salient for stimulus-driven attention. Rather, we suggest that IFP requires voluntary selection of color singletons in each consecutive trial.

Mixed signals: The effect of conflicting reward- and goal-driven biases on selective attention

Attentional selection depends on the interaction between exogenous (stimulus-driven), endogenous (goal-driven), and selection history (experience-driven) factors. While endogenous and exogenous biases have been widely investigated, less is known about their interplay with value-driven attention. The present study investigated the interaction between reward-history and goal-driven biases on perceptual sensitivity (d') and response time (RT) in a modified cueing paradigm presenting two coloured cues, followed by sinusoidal gratings. Participants responded to the orientation of one of these gratings. In Experiment 1, one cue signalled reward availability but was otherwise task irrelevant. In Experiment 2, the same cue signalled reward, and indicated the target's most likely location at the opposite side of the display. This design introduced a conflict between reward-driven biases attracting attention and goal-driven biases directing it away. Attentional effects were examined comparing trials in which cue and target appeared at the same versus opposite locations. Two interstimulus interval (ISI) levels were used to probe the time course of attentional effects. Experiment 1 showed performance benefits at the location of the reward-signalling cue and costs at the opposite for both ISIs, indicating value-driven capture. Experiment 2 showed performance benefits only for the long ISI when the target was at the opposite to the reward-associated cue. At the short ISI, only performance costs were observed. These results reveal the time course of these biases, indicating that reward-driven effects influence attention early but can be overcome later by goal-driven control. This suggests that reward-driven biases are integrated as attentional priorities, just as exogenous and endogenous factors.

Inhibition of return shortens perceived duration of a brief visual event

We investigated the influence of attentional inhibition on the perceived duration of a brief visual event. Although attentional capture by an exogenous cue is known to prolong the perceived duration of an attended visual event, it remains unclear whether time perception is also affected by subsequent attentional inhibition at the location previously cued by an exogenous cue, an attentional phenomenon known as inhibition of return. In this study, we combined spatial cuing and duration judgment. After one second from the appearance of an uninformative peripheral cue either to the left or to the right, a target appeared at a cued side in one-third of the trials, which indeed yielded inhibition of return, and at the opposite side in another one-third of the trials. In the remaining trials, a cue appeared at a central box and one second later, a target appeared at either the left or right side. The target at the previously cued location was perceived to last shorter than the target presented at the opposite location, and shorter than the target presented after the central cue presentation. Therefore, attentional inhibition produced by a classical paradigm of inhibition of return decreased the perceived duration of a brief visual event.

Impact of Mindfulness Training on Physiological Measures of Stress and Objective Measures of Attention Control in a Military Helicopter Unit

Objective: This study sought to determine if mindfulness training (MT) has a measurable impact on stress and attentional control as measured by objective physiological and psychological means.

Background: Periods of persistent, intensive work demands are known to compromise recovery and attentional capacity. The effects of 4-month MT on salivary cortisol and performance on 2 computer-based cognitive tasks were tested on a military helicopter unit exposed to a prolonged period of high workload.

Methods: MT participants were compared to a wait list control group on levels of saliva cortisol and performance on a go–no go test and a test of stimulus-driven attentional capture. Participants also reported mental demands on the go–no go test, time of wakeup, sleep duration, quality of sleep, outcome expectancies, physical activity level, self-perceived mindfulness, and symptoms of depression and anxiety.

Results: The results from a mixed between–within analysis revealed that the MT participants compared to the control group had a larger pre to post increase in high- and low-cortisol slopes, and decrease in perceived mental demand imposed by the go–no go test.

Conclusion: MT alleviates some of the physiological stress response and the subjective mental demands of challenging tasks in a military helicopter unit during a period of high workload.

Stimulus-driven attentional capture by subliminal onset cues

In two experiments, we tested whether subliminal abrupt onset cues capture attention in a stimulus-driven way. An onset cue was presented 16 ms prior to the stimulus display that consisted of clearly visible color targets. The onset cue was presented either at the same side as the target (the valid cue condition) or on the opposite side of the target (the invalid cue condition). Because the onset cue was presented 16 ms before other placeholders were presented, the cue was subliminal to the participant. To ensure that this subliminal cue captured attention in a stimulus-driven way, the cue's features did not match the top-down attentional control settings of the participants: (1) The color of the cue was always different than the color of the non-singleton targets ensuring that a top-down set for a specific color or for a singleton would not match the cue, and (2) colored targets and distractors had the same objective luminance (measured by the colorimeter) and subjective lightness (measured by flicker photometry), preventing a match between the top-down set for target and cue contrast. Even though a match between the cues and top-down settings was prevented, in both experiments, the cues captured attention, with faster response times in valid than invalid cue conditions (Experiments 1 and 2) and faster response times in valid than the neutral conditions (Experiment 2). The results support the conclusion that subliminal cues capture attention in a stimulus-driven way.

Stimulus-driven capture and contingent capture

Whether or not certain physical events can capture attention has been one of the most debated issues in the study of attention. This discussion is concerned with how goal-directed and stimulus-driven processes interact in perception and cognition. On one extreme of the spectrum is the idea that attention capture is primarily stimulus driven and automatic. On the other end is the notion that attention capture is always contingent on the goals of the observer, and thus under top-down control. This review discusses the empirical evidence for each of these viewpoints and the theoretical consequences. In addition, there is a discussion of the issues that remain controversial within the debate between the two viewpoints. It is concluded that visual selection depends on the interaction between bottom-up and top-down processes with a special role for spatial attention as the top-down gatekeeper for attention capture. WIREs Cogn Sci 2010 1 872-881 For further resources related to this article, please visit the WIREs website.

The effect of reward on orienting and reorienting in exogenous cuing

It is thought that reward-induced motivation influences perceptual, attentional, and cognitive control processes to facilitate behavioral performance. In this study, we investigated the effect of reward-induced motivation on exogenous attention orienting and inhibition of return (IOR). Attention was captured by peripheral onset cues that were nonpredictive for the target location. Participants performed a target discrimination task at short (170 ms) and long (960 ms) cue–target stimulus onset asynchronies. Reward-induced motivation was manipulated by exposing participants to low- and high-reward blocks. Typical cue facilitation effects on initial orienting were observed for both the low- and high-reward conditions. However, IOR was found only for the high-reward condition. This indicates that reward-induced motivation has a clear effect on reorienting and inhibitory processes following the initial capture of attention, but not on initial exogenous orienting that is considered to be exclusively automatic and stimulus-driven. We suggest that initial orienting is completely data-driven, not affected by top-down motivational processes, while reorienting and the accompanying IOR effect involve motivational top-down processes. To support this, we showed that reward-induced motivational processes and top-down control processes co-act in order to improve behavioral performance: High-reward-induced motivation caused an increase in top-down cognitive control, as signified by posterror slowing. Moreover, we show that personality trait propensity to reward-driven behavior (BAS-Drive scale) was related to reward-triggered behavioral changes in top-down reorienting, but not to changes in automatic orienting.

Rejection positivity predicts trial-to-trial reaction times in an auditory selective attention task: a computational analysis of inhibitory control

A series of computer simulations using variants of a formal model of attention (Melara and Algom, 2003) probed the role of rejection positivity (RP), a slow-wave electroencephalographic (EEG) component, in the inhibitory control of distraction. Behavioral and EEG data were recorded as participants performed auditory selective attention tasks. Simulations that modulated processes of distractor inhibition accounted well for reaction-time (RT) performance, whereas those that modulated target excitation did not. A model that incorporated RP from actual EEG recordings in estimating distractor inhibition was superior in predicting changes in RT as a function of distractor salience across conditions. A model that additionally incorporated momentary fluctuations in EEG as the source of trial-to-trial variation in performance precisely predicted individual RTs within each condition. The results lend support to the linking proposition that RP controls the speed of responding to targets through the inhibitory control of distractors.

Inhibition of Return Affects Contrast Sensitivity

Inhibition of return (IOR)—a slow response to targets at recently attended locations, is believed to play an important role in guiding behaviour. In the attention literature it has been shown that attentional capture by an exogenous cue affects contrast sensitivity so that it alters the appearance of low-contrast stimuli. Despite a significant amount of work over the last quarter century on IOR, it is not yet clear whether IOR operates in the same way. In the current study we examined the effect of IOR on contrast sensitivity—a very early, low-level perceptual process. We found in both a detection task and an orientation discrimination task that lower contrast was needed to detect the stimulus (Experiment 1) and determine its orientation (Experiment 2) at the cued location than at the uncued location, at short cue–target delays, while higher contrast was needed at long delays—reflecting IOR. These results clearly demonstrate that IOR affects contrast sensitivity in a similar way as attentional capture does and suggest that IOR increases perceived contrast of an object in the uncued location.

Attentional capture and inhibition of saccades after irrelevant and relevant cues

Attentional capture is usually stronger for task-relevant than irrelevant stimuli, whereas irrelevant stimuli can trigger equal or even stronger amounts of inhibition than relevant stimuli. Capture and inhibition, however, are typically assessed in separate trials, leaving it open whether or not inhibition of irrelevant stimuli is a consequence of preceding attentional capture by the same stimuli or whether inhibition is the only response to these stimuli. Here, we tested the relationship between capture and inhibition in a setup allowing for estimates of the capture and inhibition based on the very same trials. We recorded saccadic inhibition after relevant and irrelevant stimuli. At the same time, we recorded the N2pc, an event-related potential, reflecting initial capture of attention. We found attentional capture not only for, relevant but importantly also for irrelevant stimuli, although the N2pc was stronger for relevant than irrelevant stimuli. In addition, inhibition of saccades was the same for relevant and irrelevant stimuli. We conclude with a discussion of the mechanisms that are responsible for these effects.

The attentional effects of single cues and color singletons on visual sensitivity

Sudden changes in the visual periphery can automatically draw attention to their locations. For example, the brief flash of a single object (a "cue") rapidly enhances contrast sensitivity for subsequent stimuli in its vicinity. Feature singletons (e.g., a red circle among green circles) can also capture attention in a variety of tasks. Here, we evaluate whether a peripheral cue that enhances contrast sensitivity when it appears alone has a similar effect when it appears as a color singleton, with the same stimuli and task. In four experiments we asked observers to report the orientation of a target Gabor stimulus, which was preceded by an uninformative cue array consisting either of a single disk or of 16 disks containing a color or luminance singleton. Accuracy was higher and contrast thresholds lower when the single cue appeared at or near the target's location, compared with farther away. The color singleton also modulated performance but to a lesser degree and only when it appeared exactly at the target's location. Thus, this is the first study to demonstrate that cueing by color singletons, like single cues, can enhance sensory signals at an early stage of processing.

Automatic control of visual selection

This paper seeks out to reduce the role of the homunculus, the 'little man in the head' that is still prominent in most psychological theories regarding the control our behaviour. We argue that once engaged in a task (which is a volitional act), visual selection run off more or less in an automatic fashion. We argue that the salience map that drives automatic selection is not only determined by raw physical salience of the objects in the environment but also by the way these objects appear to the person. We provide evidence that priming (feature priming, priming by working memory and reward priming) sharpens the cortical representation of these objects such that these objects appear to be more salient above and beyond their physical salience. We demonstrate that this type of priming is not under volitional control: it occurs even if observers try to volitionally prepare for something else. In other words, looking at red prepares our brain for things that are red even if we volitionally try to prepare for green.

Targeting cognitive-affective risk mechanisms in stress-precipitated alcohol dependence: an integrated, biopsychosocial model of automaticity, allostasis, and addiction

This paper proposes a novel hypothetical model integrating formerly discrete theories of stress appraisal, neurobiological allostasis, automatic cognitive processing, and addictive behavior to elucidate how alcohol misuse and dependence are maintained and re-activated by stress. We outline a risk chain in which psychosocial stress initiates physiological arousal, perseverative cognition, and negative affect that, in turn, triggers automatized schema to compel alcohol consumption. This implicit cognitive process then leads to attentional biases toward alcohol, subjective experiences of craving, paradoxical increases in arousal and alcohol-related cognitions due to urge suppression, and palliative coping through drinking. When palliative coping relieves distress, it results in negative reinforcement conditioning that perpetuates the cycle by further sensitizing the system to future stressful encounters. This model has implications for development and implementation of innovative behavioral interventions (such as mindfulness training) that disrupt cognitive-affective mechanisms underpinning stress-precipitated dependence on alcohol.

Trait Mindfulness Predicts Attentional and Autonomic Regulation of Alcohol Cue-Reactivity

BACKGROUND

The trait of mindfulness varies among meditation-naïve individuals and is associated with attentional and autonomic regulation, two neurocognitive functions that become impaired in addiction. It was hypothesized that alcohol dependent inpatients with comparatively high levels of trait mindfulness would exhibit significant autonomic recovery from stress-primed alcohol cues mediated by greater attentional disengagement from such cues.

METHODS

58 alcohol dependent inpatients participated in affect-modulated psychophysiological cue-reactivity protocol and a spatial cueing task designed to assess alcohol attentional bias (AB). Associations between trait mindfulness, alcohol AB, and an index of autonomic activity, high-frequency heart rate variability (HFHRV), were examined via multivariate path analysis.

RESULTS

Higher trait mindfulness was significantly associated with less difficulty resisting the urge to drink and greater HFHRV recovery from stress-primed alcohol cues. After statistically controlling for the correlation of mindfulness and perceived difficulty resisting drinking urges, the association between mindfulness and HFHRV recovery was partially mediated by attentional disengagement from alcohol cues (model R² = .30).

DISCUSSION

Alcohol dependent inpatients higher in mindfulness are better able to disengage attention from alcohol cues, which in turn predicts the degree of HFHRV recovery from such cues. Trait mindfulness may index cognitive control over appetitive responses reflected in superior attentional and autonomic regulation of stress-primed alcohol cue-reactivity.

Top-down and bottom-up control of visual selection

The present paper argues for the notion that when attention is spread across the visual field in the first sweep of information through the brain visual selection is completely stimulus-driven. Only later in time, through recurrent feedback processing, volitional control based on expectancy and goal set will bias visual selection in a top-down manner. Here we review behavioral evidence as well as evidence from ERP, fMRI, TMS and single cell recording consistent with stimulus-driven selection. Alternative viewpoints that assume a large role for top-down processing are discussed. It is argued that in most cases evidence supporting top-down control on visual selection in fact demonstrates top-down control on processes occurring later in time, following initial selection. We conclude that top-down knowledge regarding non-spatial features of the objects cannot alter the initial selection priority. Only by adjusting the size of the attentional window, the initial sweep of information through the brain may be altered in a top-down way.

Texture segmentation: do the processing units on the saliency map increase with eccentricity?

The saliency map is a computational model and has been constructed for simulating human saliency processing, e.g. pop-out target detection (e.g. Itti & Koch, 2000). In this study the spatial structure on the saliency map was investigated. It is proposed that the saliency map is structured into processing units whose size is increasing with retinal eccentricity. In two experiments the distance between a target in the stimulus and an irrelevant structure in the mask was varied systematically. Our findings had two main points. Firstly, in texture segmentation tasks the saliency signals from two texture irregularities interfere, when these irregularities appear within a critical spatial distance. Second, the critical distances increase with target eccentricity. The eccentricity-dependent critical distances can be interpreted as crowding effects. It is assumed that additionally to the target eccentricity, also the strength of a saliency signal can determine the spatial area of its impairing influence.

Neural dynamics of attending and ignoring in human auditory cortex

Studies in all sensory modalities have demonstrated amplification of early brain responses to attended signals, but less is known about the processes by which listeners selectively ignore stimuli. Here we use MEG and a new paradigm to dissociate the effects of selectively attending, and ignoring in time. Two different tasks were performed successively on the same acoustic stimuli: triplets of tones (A, B, C) with noise-bursts interspersed between the triplets. In the COMPARE task subjects were instructed to respond when tones A and C were of same frequency. In the PASSIVE task they were instructed to respond as fast as possible to noise-bursts. COMPARE requires attending to A and C and actively ignoring tone B, but PASSIVE involves neither attending to nor ignoring the tones. The data were analyzed separately for frontal and auditory-cortical channels to independently address attentional effects on low-level sensory versus putative control processing. We observe the earliest attend/ignore effects as early as 100 ms post-stimulus onset in auditory cortex. These appear to be generated by modulation of exogenous (stimulus-driven) sensory evoked activity. Specifically related to ignoring, we demonstrate that active-ignoring-induced input inhibition involves early selection. We identified a sequence of early (<200 ms post-onset) auditory cortical effects, comprised of onset response attenuation and the emergence of an inhibitory response, and provide new, direct evidence that listeners actively ignoring a sound can reduce their stimulus related activity in auditory cortex by 100 ms after onset when this is required to execute specific behavioral objectives.

Brain structures involved in visual search in the presence and absence of color singletons

It is still debated to what degree top-down and bottom-up driven attentional control processes are subserved by shared or by separate mechanisms. Interactions between these attentional control forms were investigated using a rapid event-related fMRI design, using an attentional search task. Following a prestimulus mask, target stimuli (consisting of a letter C or a mirror image of the C, enclosed in a diamond outline) were presented either at one unique location among three nontarget items (consisting of a random letter, enclosed in a circle outline; 50% probability), or at all four possible target locations (also 50% probability). On half the trials, irrelevant color singletons were presented, consisting of a color change of one of the four prestimulus masks, just prior to target appearance. Participants were required to search for a target letter inside the diamond and report its orientation. Results indicate that, in addition to a common network of parietal areas, medial frontal cortex is uniquely involved in top-down orienting, whereas bottom-up control is mainly subserved by a network of occipital and parietal areas. Additionally, we found that participants who were better able to suppress orienting to the color singleton showed middle frontal gyrus activation, and that the degree of top-down control correlated with insular activity. We conclude that, in addition to a common set of parietal areas, separate brain areas are involved in top-down and bottom-up driven attentional control, and that frontal areas play a role in the suppression of attentional capture by an irrelevant color singleton.

Displaywide visual features associated with a search display’s appearance can mediate attentional capture

Whether or not the capture of visual attention is driven solely by the salience of an attention-capturing stimulus or mediated by top-down control has been a point of contention since Folk, Remington, and Johnston (1992) introduced their contingent involuntary orienting hypothesis, which states that the capture of attention by a salient stimulus depends on its relevance to a feature distinguishing the target from nontargets. Gibson and Kelsey (1998) extended Folk et al.'s (1992) hypothesis by demonstrating that features associated with the appearance of the target display also mediate capture. Although similar to Folk et al. (1992), Gibson and Kelsey's displaywide contingent orienting hypothesis makes it difficult to demonstrate stimulus-driven capture, because an observer must always use some perceptible feature as a signal of the target display's appearance; hence, such features could always be mediating capture. The present article reviews and applies the logic of Gibson and Kelsey's and Folk et al.'s (1992) hypotheses to experiments from the attentional capture literature, and assesses whether previously reported capture effects were mediated by top-down attentional control. It concludes that these capture effects were not stimulus-driven.