Can the processing of task-irrelevant threatening stimuli be inhibited? - The role of shape and valence in the saliency of threatening objects

Numerous studies have demonstrated that attention is quickly oriented towards threatening stimuli, and that this attentional bias is difficult to inhibit. The root cause(s) of this bias may be attributable to the affective (e.g., valence) or visual features (e.g., shape) of threats. In two experiments (behavioral, eye-tracking), we tested which features play a bigger role in the salience of threats. In both experiments, participants looked for a neutral target (butterfly, lock) among other neutral objects. In half of the trials a threatening (snake, gun) or nonthreatening (but visually similar; worm, hairdryer) task-irrelevant distractor was also present at a near or far distance from the target. Behavioral results indicate that both distractor types interfered with task performance. Rejecting nonthreatening distractors as nontargets was easier when they were presented further from the target but distance had no effect when the distractor was threatening. Eye-tracking results showed that participants fixated less often (and for less time) on threatening compared to nonthreatening distractors. They also viewed targets for less time when a threatening distractor was present (compared to nonthreatening). Results suggest that visual features of threats are easier to suppress than affective features, and the latter may have a stronger role in eliciting attentional biases.

Early neural potentiation to centrally and peripherally presented fear-conditioned faces

For humans, it is vitally important to rapidly detect and process threatening signals regardless of whether stimuli occur at fixation or in the periphery. However, it is unknown whether eccentricity affects early neuronal electrophysiological responses to fear-conditioned stimuli. We examined early event-related potentials (ERPs) of the electroencephalogram (EEG) to fear-conditioned faces to address this question. Participants (N = 80) were presented with faces, either paired with an aversive (CS+) or neutral sound (CS-), at central or peripheral positions. We ensured constant central fixation using online eye-tracking but directed attention to either centrally or peripherally presented faces. Manipulation checks showed successful fear-conditioning (i.e., on average lower ratings in valence and higher ratings in arousal and perceived threat) and successful shifts of visuospatial attention indexed by high task performance and pre-stimulus alpha lateralization of the EEG spectra. We observed a generally increased P1 to fear-conditioned faces regardless of presentation location. An N170 difference between fear-conditioned and neutral stimuli was found but was restricted to the central location and depended on the effectivity of fear-conditioning. A similar effect was observed for the early posterior negativity (EPN). Trait anxiety was not related to differential ERP responses to CS+ versus CS- faces for any ERP component. These findings suggest that the P1 indexes early responses to centrally and peripherally presented fear-conditioned faces. Subsequent stages are modulated by the spatial location of the stimuli. This suggests different stages of neural processing of fear-conditioned faces depending on their spatial location. Finally, our results question the hypothesis that trait anxiety in healthy participants is related to altered visual processing of fear-conditioned faces.

A generative adversarial model of intrusive imagery in the human brain

The mechanisms underlying the subjective experiences of mental disorders remain poorly understood. This is partly due to long-standing over-emphasis on behavioral and physiological symptoms and a de-emphasis of the patient's subjective experiences when searching for treatments. Here, we provide a new perspective on the subjective experience of mental disorders based on findings in neuroscience and artificial intelligence (AI). Specifically, we propose the subjective experience that occurs in visual imagination depends on mechanisms similar to generative adversarial networks that have recently been developed in AI. The basic idea is that a generator network fabricates a prediction of the world, and a discriminator network determines whether it is likely real or not. Given that similar adversarial interactions occur in the two major visual pathways of perception in people, we explored whether we could leverage this AI-inspired approach to better understand the intrusive imagery experiences of patients suffering from mental illnesses such as post-traumatic stress disorder (PTSD) and acute stress disorder. In our model, a nonconscious visual pathway generates predictions of the environment that influence the parallel but interacting conscious pathway. We propose that in some patients, an imbalance in these adversarial interactions leads to an overrepresentation of disturbing content relative to current reality, and results in debilitating flashbacks. By situating the subjective experience of intrusive visual imagery in the adversarial interaction of these visual pathways, we propose testable hypotheses on novel mechanisms and clinical applications for controlling and possibly preventing symptoms resulting from intrusive imagery.

Exogenous Attention to Emotional Stimuli Presenting Realistic (3D) Looming Motion

Previous research shows that dynamic stimuli, on the one hand, and emotional stimuli, on the other, capture exogenous attention due to their biological relevance. Through neural (ERPs) and behavioral measures (reaction times and errors), the present study explored the combined effect of looming motion and emotional content on attentional capture. To this end, 3D-recreated static and dynamic animals assessed as emotional (positive or negative) or neutral were presented as distractors while 71 volunteers performed a line orientation task. We observed a two-phase effect: firstly (before 300 ms), early components of ERPs (P1p and N2po) showed enhanced exogenous attentional capture by looming positive distractors and static threatening animals. Thereafter, dynamic and static threatening distractors received enhanced endogenous attention as revealed by both late ERP activity (LPC) and behavioral (errors) responses. These effects are likely explained by both the emotional valence and the distance of the stimulus at each moment.

The effects of task-irrelevant threatening stimuli on orienting- and executive attentional processes under cognitive load

Human visual attention is biased to rapidly detect threats in the environment so that our nervous system can initiate quick reactions. The processes underlying threat detection (and how they operate under cognitive load), however, are still poorly understood. Thus, we sought to test the impact of task-irrelevant threatening stimuli on the salience network and executive control of attention during low and high cognitive load. Participants were exposed to neutral or threatening pictures (with moderate and high arousal levels) as task-irrelevant distractors in near (parafoveal) and far (peripheral) positions while searching for numbers in ascending order in a matrix array. We measured reaction times and recorded eye-movements. Our results showed that task-irrelevant distractors primarily influenced behavioural measures during high cognitive load. The distracting effect of threatening images with moderate arousal level slowed reaction times for finding the first number. However, this slowing was offset by high arousal threatening stimuli, leading to overall shorter search times. Eye-tracking measures showed that participants fixated threatening pictures more later and for shorter durations compared to neutral images. Together, our results indicate a complex relationship between threats and attention that results not in a unitary bias but in a sequence of effects that unfold over time.

Suppression of alpha-band power underlies exogenous attention to emotional distractors

Alpha-band oscillations (8-14 Hz) are essential for attention and perception processes by facilitating the selection of relevant information. Directing visuospatial endogenous (voluntary) attention to a given location consistently results in a power suppression of alpha activity over occipito-parietal areas contralateral to the attended visual field. In contrast, the neural oscillatory dynamics underlying the involuntary capture of attention, or exogenous attention, are currently under debate. By exploiting the inherent capacity of emotionally salient visual stimuli to capture attention, we aimed to investigate whether exogenous attention is characterized by either a reduction or an increase in alpha-band activity. Electroencephalographic activity was recorded while participants completed a Posner visuospatial cueing task, in which a lateralized image with either positive, negative, or neutral emotional content competed with a target stimulus presented in the opposite hemifield. Compared with trials with no distractors, alpha power was reduced over occipital regions contralateral to distracting images. This reduction of alpha activity turned out to be functionally relevant, as it correlated with impaired behavioral performance on the ongoing task and was enhanced for distractors with negative valence. Taken together, our results demonstrate that visuospatial exogenous attention is characterized by a suppression of alpha-band activity contralateral to distractor location, similar to the oscillatory underpinnings of endogenous attention. Further, these results highlight the key role of exogenous attention as an adaptive mechanism for the efficient detection of biologically salient stimuli.

Exploration of Exogenous Attention to Disgust and Fear Pictures with Different Spatial Frequencies Through Event-related Potentials

The study of the effects of fear and disgust on the capture of automatic attention is gaining interest. Most findings reveal a more efficient capture of exogenous attention by disgust than by fear stimuli, although the underlying mechanisms are not completely understood. The manipulation of their spatial frequency may provide new insight that may contribute to clarify this issue. The present study aimed to explore differential processing of disgust and fear scenes containing only low spatial frequencies (LSF) or all spatial frequencies (intact) presented as distractors in an exogenous attention task. Event-related potentials (ERPs) and behavioral responses were recorded as dependent variables from forty participants (29 women). The results showed that disgust and fear distractors captured exogenous attention equally early, as indicated by the augmented amplitude of the N2p, and later disgust distractors are the ones eliciting the highest amplitude of the LPP component. While in an initial stage, both stimuli seem to have similar preferential access to further processing allowing fast responding in both cases, disgust is more deeply processed at a later stage probably facilitating its examination. These findings suggest that exploring the temporal course of processing is relevant for the understanding of the differential capture of exogenous attention by disgust and fear distractors.

Early ERP functions are indexed by lateralized effects to peripherally presented emotional faces and scrambles

A large body of research suggests that early event-related potentials (ERPs), such as the P1 and N1, are potentiated by attention and represent stimulus amplification. However, recent accounts suggest that the P1 is associated with inhibiting the irrelevant visual field evidenced by a pronounced ipsilateral P1 during sustained attention to peripherally presented stimuli. The current EEG study further investigated this issue to reveal how lateralized ERP findings are modulated by face and emotional information. Therefore, participants were asked to fixate the center of the screen and pay sustained attention either to the right or left visual field, where angry or neutral faces or their Fourier phase-scrambled versions were presented. We found a bilateral P1 to all stimuli with relatively increased, but delayed, ipsilateral P1 amplitudes to faces but not to scrambles. Explorative independent component analyses dissociated an earlier lateralized larger contralateral P1 from a later bilateral P1. By contrast, the N170 showed a contralateral enhancement to all stimuli, which was most pronounced for neutral faces attended in the left hemifield. Finally, increased contralateral alpha power was found for both attended hemifields but was not significantly related to poststimulus ERPs. These results provide evidence against a general inhibitory role of the P1 but suggest stimulus-specific relative enhancements of the ipsilateral P1 for the irrelevant visual hemifield. The lateralized N170, however, is associated with stimulus amplification as a function of facial features.

Photographs of Actions: What Makes Them Special Cues to Social Perception

I have reviewed studies on neural responses to pictured actions in the action observation network (AON) and the cognitive functions of these responses. Based on this review, I have analyzed the specific representational characteristics of action photographs. There has been consensus that AON responses provide viewers with knowledge of observed or pictured actions, but there has been controversy about the properties of this knowledge. Is this knowledge causally provided by AON activities or is it dependent on conceptual processing? What elements of actions does it refer to, and how generalized or specific is it? The answers to these questions have come from studies that used transcranial magnetic stimulation (TMS) to stimulate motor or somatosensory cortices. In conjunction with electromyography (EMG), TMS allows researchers to examine changes of the excitability in the corticospinal tract and muscles of people viewing pictured actions. The timing of these changes and muscle specificity enable inferences to be drawn about the cognitive products of processing pictured actions in the AON. Based on a review of studies using TMS and other neuroscience methods, I have proposed a novel hypothetical account that describes the characteristics of action photographs that make them effective cues to social perception. This account includes predictions that can be tested experimentally.

Organization of directed functional connectivity among nodes of ventral attention network reveals the common network mechanisms underlying saliency processing across distinct spatial and spatio-temporal scales

Previous neuroimaging studies have extensively evaluated the structural and functional connectivity of the Ventral Attention Network (VAN) and its role in reorienting attention in the presence of a salient (pop-out) stimulus. However, a detailed understanding of the "directed" functional connectivity within the VAN during the process of reorientation remains elusive. Functional magnetic resonance imaging (fMRI) studies have not adequately addressed this issue due to a lack of appropriate temporal resolution required to capture this dynamic process. The present study investigates the neural changes associated with processing salient distractors operating at a slow and a fast time scale using custom-designed experiment involving visual search on static images and dynamic motion tracking, respectively. We recorded high-density scalp electroencephalography (EEG) from healthy human volunteers, obtained saliency-specific behavioral and spectral changes during the tasks, localized the sources underlying the spectral power modulations with individual-specific structural MRI scans, reconstructed the waveforms of the sources and finally, investigated the causal relationships between the sources using spectral Granger-Geweke Causality (GGC). We found that salient stimuli processing, across tasks with varying spatio-temporal complexities, involves a characteristic modulation in the alpha frequency band which is executed primarily by the nodes of the VAN constituting the temporo-parietal junction (TPJ), the insula and the lateral prefrontal cortex (lPFC). The directed functional connectivity results further revealed the presence of bidirectional interactions among prominent nodes of right-lateralized VAN, corresponding only to the trials with saliency. Thus, our study elucidates the invariant network mechanisms for processing saliency in visual attention tasks across diverse time-scales.

Understanding the capture of exogenous attention by disgusting and fearful stimuli: The role of interoceptive accuracy

The aim of the study was to explore the role of interoceptive accuracy (IA) on exogenous attention to disgusting and fearful distractors of a main concurrent task. Participants were thirty university students previously identified as high (N = 16) or normal IA according their performance in a heartbeat detection task. Event-related potentials and behavioural responses were recorded. The results showed that disgusting stimuli capture exogenous attention in a first stage as reflected by the augmented amplitude of the P100 component of the ERPs in high IA participants. Fearful distractors may capture attention in a later moment in all participants as revealed by a marginally significant effect on the amplitude of N200. At behavioural level, disgusting distractors provoked a higher number of errors than neutral in normal IA participants. The time course of the effect of disgust and fearful eliciting distractors on exogenous attention appeared to depend on the individual characteristic of participants.

Retinotopy of emotion: Perception of negatively valenced stimuli presented at different spatial locations as revealed by event-related potentials

Scarce previous data on how the location where an emotional stimulus appears in the visual scene modulates its perception suggest that, for functional reasons, a perceptual advantage may exist, vertically, for stimuli presented at the lower visual field (LoVF) and, horizontally, for stimuli presented at the left visual field (LeVF). However, this issue has been explored through a limited number of spatial locations, usually in a single spatial dimension (e.g., horizontal) and invariant eccentricities. Event-related potentials (ERPs) were recorded from 39 participants perceiving brief neutral (wheels) and emotional stimuli (spiders) presented at 17 different locations, one foveal and 16 at different peripheral coordinates. As a secondary scope, we explored the role of the magnocellular (M) and the parvocellular (P) visual pathways by presenting an isoluminant/heterochromatic (P-biased) and a heteroluminant/isochromatic version (M-biased) of each stimulus. Emo > Neu effects were observed in PN1 (120 ms) for stimuli located at fovea, and in PN2 (215 ms) for stimuli located both at fovea and diverse peripheral regions. A factorial approach to these effects further revealed that: (a) emotional stimuli presented in the periphery are efficiently perceived, without evident decrease from para- to perifovea; (b) peripheral Emo > Neu effects are reflected 95 ms later than foveal Emo > Neu effects in ERPs; (c) LoVF is more involved than UVF in these effects; (d) our data fail to support the LeVF advantage previously reported, and (e) Emo > Neu effects were significant for both M and P stimuli.

Magnocellular and parvocellular pathway contributions to facial threat cue processing

Human faces evolved to signal emotions, with their meaning contextualized by eye gaze. For instance, a fearful expression paired with averted gaze clearly signals both presence of threat and its probable location. Conversely, direct gaze paired with facial fear leaves the source of the fear-evoking threat ambiguous. Given that visual perception occurs in parallel streams with different processing emphases, our goal was to test a recently developed hypothesis that clear and ambiguous threat cues would differentially engage the magnocellular (M) and parvocellular (P) pathways, respectively. We employed two-tone face images to characterize the neurodynamics evoked by stimuli that were biased toward M or P pathways. Human observers (N = 57) had to identify the expression of fearful or neutral faces with direct or averted gaze while their magnetoencephalogram was recorded. Phase locking between the amygdaloid complex, orbitofrontal cortex (OFC) and fusiform gyrus increased early (0–300 ms) for M-biased clear threat cues (averted-gaze fear) in the β-band (13–30 Hz) while P-biased ambiguous threat cues (direct-gaze fear) evoked increased θ (4–8 Hz) phase locking in connections with OFC of the right hemisphere. We show that M and P pathways are relatively more sensitive toward clear and ambiguous threat processing, respectively, and characterize the neurodynamics underlying emotional face processing in the M and P pathways.

Does Threat Have an Advantage After All? - Proposing a Novel Experimental Design to Investigate the Advantages of Threat-Relevant Cues in Visual Processing

The automatic visual attentional procession of threatening stimuli over non-threatening cues has long been a question. The so-called classical visual search task (VST) has quickly become the go-to paradigm to investigate this. However, the latest results showed that the confounding results could originate from the shortcomings of the VST. Thus, here we propose a novel approach to the behavioral testing of the threat superiority effect. We conducted two experiments using evolutionary relevant and modern real-life scenes (e.g., forest or street, respectively) as a background to improve ecological validity. Participants had to find different targets in different spatial positions (close to fovea or periphery) using a touch-screen monitor. In Experiment 1 participants had to find the two most often used exemplar of the evolutionary and modern threatening categories (snake and gun, respectively), or neutral objects of the same category. In Experiment 2 we used more exemplars of each category. All images used were controlled for possible confounding low-level visual features such as contrast, frequency, brightness, and image complexity. In Experiment 1, threatening targets were found faster compared to neutral cues irrespective of the evolutionary relevance. However, in Experiment 2, we did not find an advantage for threatening targets over neutral ones. In contrast, the type of background, and spatial position of the target only affected the detection of neutral targets. Our results might indicate that some stimuli indeed have an advantage in visual processing, however, they are not highlighted based on evolutionary relevance of negative valence alone, but rather through different associational mechanisms.

Towards a Dynamic Exploration of Vision, Cognition and Emotion in Alcohol-Use Disorders

Abstract: Visuoperceptive impairments are among the most frequently reported deficits in alcohol-use disorders, but only very few studies have investigated their origin and interactions with other categories of dysfunctions. Besides, these deficits have generally been interpreted in a linear bottom-up perspective, which appears very restrictive with respect to the new models of vision developed in healthy populations. Indeed, new theories highlight the predictive nature of the visual system and demonstrate that it interacts with higher-level cognitive functions to generate top-down predictions. These models nota-bly posit that a fast but coarse visual analysis involving magnocellular pathways helps to compute heuristic guesses regard-ing the identity and affective value of inputs, which are used to facilitate conscious visual recognition. Building on these new proposals, the present review stresses the need to reconsider visual deficits in alcohol-use disorders as they might have cru-cial significance for core features of the pathology, such as attentional bias, loss of inhibitory control and emotion decoding impairments. Centrally, we suggest that individuals with severe alcohol-use disorders could present with magnocellular dam-age and we defend a dynamic explanation of the deficits. Rather than being restricted to high-level processes, deficits could start at early visual stages and then extend and potentially intensify during following steps due to reduced cerebral connec-tivity and dysfunctional cognitive/emotional regions. A new research agenda is specifically provided to test these hypotheses.