Mandatory processing of irrelevant fearful face features in visual search

Faces expressing fear may attract attention in an automatic bottom-up fashion. Here we address this issue with magneto-encephalographic (MEG) recordings in subjects performing a demanding visual search combined with the presentation of irrelevant neutral or fearful faces. The impact of the faces 'emotional expression on attentional selection was assessed by analyzing the N2pc component-a modulation of the event-related magnetic field response known to reflect attentional focusing in visual search. We observed that lateralized fearful faces elicited an N2pc approximately between 240 and 400 msec in ventral extrastriate cortex that was independent of the N2pc reflecting target selection in visual search. Despite their clear influence on neural processing, fearful faces did not significantly influence behavioral performance. To clarify this discrepancy, we further performed an MEG experiment in which the demands of the search task were reduced. Under those conditions, lateralized fearful faces elicited an N2pc response that was again independent of the N2pc response to the search target. Behavioral performance was, however, influenced in a significant manner, suggesting that for behavioral effects to appear, sufficient attentional resources need to be left unoccupied by the search task-a notion put forward by the perceptual load theory. Our observations are taken to indicate that irrelevant fearful faces influence attentional processing in extrastriate visual cortex in an automatic fashion and independent of other task-relevant attentional operations. However, this may not necessarily be echoed at the behavioral level as long as task-relevant selection operations exhaust attentional resources

The role of stimulus salience and attentional capture across the neural hierarchy in a stop-signal task

Inhibitory motor control is a core function of cognitive control. Evidence from diverse experimental approaches has linked this function to a mostly right-lateralized network of cortical and subcortical areas, wherein a signal from the frontal cortex to the basal ganglia is believed to trigger motor-response cancellation. Recently, however, it has been recognized that in the context of typical motor-control paradigms those processes related to actual response inhibition and those related to the attentional processing of the relevant stimuli are highly interrelated and thus difficult to distinguish. Here, we used fMRI and a modified Stop-signal task to specifically examine the role of perceptual and attentional processes triggered by the different stimuli in such tasks, thus seeking to further distinguish other cognitive processes that may precede or otherwise accompany the implementation of response inhibition. In order to establish which brain areas respond to sensory stimulation differences by rare Stop-stimuli, as well as to the associated attentional capture that these may trigger irrespective of their task-relevance, we compared brain activity evoked by Stop-trials to that evoked by Go-trials in task blocks where Stop-stimuli were to be ignored. In addition, region-of-interest analyses comparing the responses to these task-irrelevant Stop-trials, with those to typical relevant Stop-trials, identified separable activity profiles as a function of the task-relevance of the Stop-signal. While occipital areas were mostly blind to the task-relevance of Stop-stimuli, activity in temporo-parietal areas dissociated between task-irrelevant and task-relevant ones. Activity profiles in frontal areas, in turn, were activated mainly by task-relevant Stop-trials, presumably reflecting a combination of triggered top-down attentional influences and inhibitory motor-control processes

The Role of Stimulus Salience and Attentional Capture Across the Neural Hierarchy in a Stop-Signal Task

Inhibitory motor control is a core function of cognitive control. Evidence from diverse experimental approaches has linked this function to a mostly right-lateralized network of cortical and subcortical areas, wherein a signal from the frontal cortex to the basal ganglia is believed to trigger motor-response cancellation. Recently, however, it has been recognized that in the context of typical motor-control paradigms those processes related to actual response inhibition and those related to the attentional processing of the relevant stimuli are highly interrelated and thus difficult to distinguish. Here, we used fMRI and a modified Stop-signal task to specifically examine the role of perceptual and attentional processes triggered by the different stimuli in such tasks, thus seeking to further distinguish other cognitive processes that may precede or otherwise accompany the implementation of response inhibition. In order to establish which brain areas respond to sensory stimulation differences by rare Stop-stimuli, as well as to the associated attentional capture that these may trigger irrespective of their task-relevance, we compared brain activity evoked by Stop-trials to that evoked by Go-trials in task blocks where Stop-stimuli were to be ignored. In addition, region-of-interest analyses comparing the responses to these task-irrelevant Stop-trials, with those to typical relevant Stop-trials, identified separable activity profiles as a function of the task-relevance of the Stop-signal. While occipital areas were mostly blind to the task-relevance of Stop-stimuli, activity in temporo-parietal areas dissociated between task-irrelevant and task-relevant ones. Activity profiles in frontal areas, in turn, were activated mainly by task-relevant Stop-trials, presumably reflecting a combination of triggered top-down attentional influences and inhibitory motor-control processes

The color red attracts attention in an emotional context : an ERP study

The color red is known to influence psychological functioning, having both negative (e.g., blood, fire, danger), and positive (e.g., sex, food) connotations. The aim of our study was to assess the attentional capture by red-colored images, and to explore the modulatory role of the emotional valence in this process, as postulated by Elliot and Maier (2012) color-in-context theory. Participants completed a dot-probe task with each cue comprising two images of equal valence and arousal, one containing a prominent red object and the other an object of different coloration. Reaction times were measured, as well as the event-related lateralizations of the EEG. Modulation of the lateralized components revealed that the color red captured and later held the attention in both positive and negative conditions, but not in a neutral condition. An overt motor response to the target stimulus was affected mainly by attention lingering over the visual field where the red cue had been flashed. However, a weak influence of the valence could still be detected in reaction times. Therefore, red seems to guide attention, specifically in emotionally-valenced circumstances, indicating that an emotional context can alter color’s impact both on attention and motor behavior

Processing Facial Attractiveness Without Central Attention: Evidence from Electrophysiological Measures

Jung, Ruthruff, Tybur, Gaspelin, and Miller (2012) reported behavioral evidence that the perception of facial attractiveness requires central attentional resources. We evaluated this conclusion using more sensitive electrophysiological measures. Participants first made an attractiveness rating on faces to validate the assigned level of attractiveness (low vs. high). They then performed a dual-task experiment. The purpose of Task 1, a tone/noise discrimination, was to use up central attentional resources. For Task 2, one attractive face and one less-attractive face were presented side-by-side, and participants indicated the location of the more attractive face. The stimulus onset asynchrony (SOA) between the two tasks was 50, 200, or 1,000 ms. The N2pc elicited by Task-2 attractive face was used to track the allocation of spatial attention over time. Although we observed the usual postponement of behavioral responses at short SOAs, we did not observe any postponement of the N2pc elicited by the more attractive face. We thus conclude, contrary to previous behavioral studies, that attractiveness can be judged automatically, even while central attentional resources are still allocated to Task 1. Key Words: Facial Attractiveness, Central Attention, N2pc, Even-Related Potentials, PR

Attentional bias modification in social anxiety: Effects on the N2pc component

Several meta-analyses to date have confirmed the efficacy of attentional bias modification (ABM) in shifting reaction times away from threatening stimuli, reducing anxiety symptoms, and buffering against stressor vulnerability. The reliability of reaction time differences, however, has been found to show unacceptable psychometric properties. In this study, we tested the impact of an extensive Dot-Probe ABM procedure, consisting of close to 7000 trials, concurrently with behavioral and electrophysiological measures within a large sample of over 100 highly socially anxious participants. Results indicated that the N2pc component demonstrates superior internal consistency and more statistical power in detecting attentional biases and their modification than reaction time (RT) differences. RTs were neither indicative of an attentional bias before ABM nor of a modification over time. In contrast, the N2pc indexed both an initial attentional preference for threatening stimuli and an alteration of this relationship after training. Outcomes were not specific for attentional training away from threat but also occurred in the no-contingency control procedure, casting doubt on the theoretic underpinnings of ABM. Electrophysiological measures are an important complement to the ABM literature and should be further utilized to assess attentional biases with excellent reliability

Capture by Fear Revisited: An Electrophysiological Investigation

The present study, using a cuing paradigm, reexamined the claim of an attentional bias toward fearful faces. In Experiment 1, participants searched a target display for a letter in a specific color. This target display was preceded by a non-informative cue display, which contained colored boxes (one in the target color and one in the distractor color) or emotional faces (one fearful face and one neutral face). Each cue could appear in the same location as the target (validly cued) or different (invalidly cued). To determine whether the cues captured attention, we used an electrophysiological measure of spatial attention known as the N2pc effect. The target color cue produced a substantial N2pc effect and a robust cue validity effect on behavioral data, indicating capture by stimuli that match what participants are looking for. However, neither effect was present for the task-irrelevant fearful face cue. These findings suggest that negative stimuli (such as fearful facial expressions) do not generally have the inherent power to capture spatial attention against our will. Experiment 2 showed that these same fearful faces could capture attention when fearful expressions became task-relevant. Thus, the critical determinant of capture appears to be task-relevance, rather than perceived threat.Keywords: Attention Capture, N2pc, Visual Attention, Emotion Perceptio

Target and distractor processing and the influence of load on the allocation of attention to task-irrelevant threat

This study investigated the characteristics of two distinct mechanisms of attention – stimulus enhancement and stimulus suppression – using an event-related potential (ERP) approach. Across three experiments, participants viewed sparse visual search arrays containing one target and one distractor. The main results of Experiments 1 and 2 revealed that whereas neural signals for stimuli that are not inherently salient could be directly suppressed without prior attentional enhancement, this was not the case for stimuli with motivational relevance (human faces). Experiment 3 showed that as task difficulty increased, so did the need for suppression of distractor stimuli. It also showed the preferential attentional enhancement of angry over neutral distractor faces, but only under conditions of high task difficulty, suggesting that the effects of distractor valence on attention are greatest when there are fewer available resources for distractor processing. The implications of these findings are considered in relation to contemporary theories of attention

An electrophysiological study of emotional perception in a dual-task paradigm

The present study examined whether emotion perception requires central attentional resources. A dual-task paradigm was used to examine whether people can direct their attention to a face expressing a target emotion, even while they are still selecting a response to another task. Task-1 required an auditory discrimination while for Task-2, one happy face and one angry face were presented adjacent to each other. Participants were asked to find the face with a pre-specified emotion and indicate its gender (Experiment 1), location (Experiment 2), or identify whether the faces were the same gender or different gender without emotional goal settings (Experiment 3). The stimulus onset asynchrony (SOA) between the two tasks was varied. To determine where people were attending, an electrophysiological measure of attention known as the N2pc component of the event-related brain potential was used. The face expressing the target emotion elicited an N2pc effect, indicating attention capture, even when participants were already pre-occupied with processing Task-1 (i.e., short SOAs). Thus, it appears that emotion perception can occur even when central attentional resources are unavailable. In addition, angry faces elicited a much larger N2pc effect than happy faces, indicating an attentional bias toward negative emotions

Attention Capture by Angry Faces Depends on the Distribution of Attention

The threat-capture hypothesis posits a threat-detection system that automatically directs visual attention to threat-related stimuli (e.g., angry facial expressions) in the environment. Importantly, this system is theorised to operate preattentively, processing all input across the visual field in parallel, prior to the operation of selective attention. The threat-capture hypothesis generates two predictions. First, because the threat-detection system directs attention to threat automatically, threat stimuli should capture attention when they are task-irrelevant and the observer has no intention to attend to them. Second, because the threat-detection system operates preattentively, threat stimuli should capture attention even when it is engaged elsewhere. This thesis tested these predictions using behavioural measures of attention capture in conjunction with the N2pc, an event-related potential (ERP) index of attention selection. Experiment 1 tested the first prediction of the threat-capture hypothesis – that threat stimuli capture attention when they are task-irrelevant. Participants performed a dot-probe task in which pairs of face cues – one angry and one neutral – preceded a lateral target. On some trials, the faces were Fourier phase-scrambled to control for low-level visual properties. Consistent with the threat-capture hypothesis, an N2pc was observed for angry faces, suggesting they captured attention despite being completely task-irrelevant. Interestingly, this effect remained when faces were Fourier phase-scrambled, suggesting it is low-level visual properties that drive attention capture by angry faces. Experiments 2A and 2B tested the second prediction of the threat capture hypothesis – that threat stimuli capture attention when it is engaged elsewhere. Participants performed a primary task in which they searched a column of letters at fixation for a target letter. The perceptual load of this task was manipulated to ensure that attentional resources were consumed by this task. Thus there were high and low perceptual load conditions in these experiments. Task-irrelevant angry faces interfered with task performance when the perceptual load of the task was high but not when it was low (Experiment 2A). Similarly, angry faces elicited an N2pc, indicating that they captured attention, but only when perceptual load was high and when faces were phase-scrambled (Experiment 2B). These experiments further suggest that low-level visual factors are important in attention capture by angry faces. These results appear to be inconsistent with the threat-capture hypothesis, and suggest that angry faces do not necessarily capture attention when it is engaged elsewhere