Attentional bias toward negative stimuli in PTSD: an eye-tracking study.

BACKGROUND: Research on biased processing of aversive stimuli in posttraumatic stress disorder (PTSD) has produced inconsistent results between response time (RT) and eye-tracking studies. Recent RT-based results of dot-probe studies showed no attentional bias (AB) for threat while eye-tracking research suggested heightened sustained attention for this information. Here, we used both RT-based and eye-tracking measures to explore the dynamics of AB to negative stimuli in PTSD. METHODS: Twenty-three individuals diagnosed with PTSD, 23 trauma-exposed healthy controls, and 23 healthy controls performed an emotional dot-probe task with pairs of negative and neutral scenes presented for either 1 or 2 s. Analyses included eye movements during the presentation of the scenes and RT associated with target localization. RESULTS: There was no evidence for an AB toward negative stimuli in PTSD from RT measures. However, the main eye-tracking results revealed that all three groups showed longer dwell times on negative pictures than neutral pictures at 1 s and that this AB was stronger for individuals with PTSD. Moreover, although AB disappeared for the two groups of healthy controls with prolonged exposure, it persisted for individuals with PTSD. CONCLUSION: PTSD is associated with an AB toward negative stimuli, characterized by heightened sustained attention toward negative scenes once detected. This study sheds light on the dynamics of AB to negative stimuli in PTSD and encourages us to consider optimized therapeutic interventions targeting abnormal AB patterns.

The contributions of central and peripheral vision to scene-gist recognition with a 180° visual field.

We investigated the relative contributions of central versus peripheral vision in scene-gist recognition with panoramic 180° scenes. Experiment 1 used the window/scotoma paradigm of Larson and Loschky (2009). We replicated their findings that peripheral vision was more important for rapid scene categorization, while central vision was more efficient, but those effects were greatly magnified. For example, in comparing our critical radius (which produced equivalent performance with mutually exclusive central and peripheral image regions) to that of Larson and Loschky, our critical radius of 10° had a ratio of central to peripheral image area that was 10 times smaller. Importantly, we found different functional relationships between the radius of centrally versus peripherally presented imagery (or the proportion of centrally versus peripherally presented image area) and scene-categorization sensitivity. For central vision, stimulus discriminability was an inverse function of image radius, while for peripheral vision the relationship was essentially linear. In Experiment 2, we tested the photographic-bias hypothesis that the greater efficiency of central vision for rapid scene categorization was due to more diagnostic information in the center of photographs. We factorially compared the effects of the eccentricity from which imagery was sampled versus the eccentricity at which imagery was presented. The presentation eccentricity effect was roughly 3 times greater than the sampling eccentricity effect, showing that the central-vision efficiency advantage was primarily due to the greater sensitivity of central vision. We discuss our results in terms of the eccentricity-dependent neurophysiology of vision and discuss implications for computationally modeling rapid scene categorization.

What Is the Nature of the Reach and Grasp Deficit in Wet Age-related Macular Degeneration?

SIGNIFICANCE: Vision is paramount for motor actions directed toward objects. Vision allows not only the identification of objects and their shape and spatial location, but also the adaptation of our movement when it arrives on the object. These findings show that vision deficits, as in age-related macular degeneration (AMD), can lead to reaching and grasping deficits. PURPOSE: Few studies have investigated reaching and grasping in patients with AMD. They showed a deficit in the execution of motor actions in people with AMD, even though these people do not mention difficulties in their daily lives. The purpose of this study was to understand the nature of impairments in motor actions in patients. METHODS: We compared performance in two reach-and-grasp tasks determined by whether the participants (16 people with wet AMD and 17 age-matched control subjects) had time to look at the object before reaching and grasping it. RESULTS: The results show that the kinematic parameters of reach-and-grasp movements do not differ between groups when participants are provided time to look at the object before the movement. In contrast, performance in terms of movement duration, acceleration time, time to reach the maximum grip aperture, and the maximum velocity differ between patients and control subjects when the object is displayed immediately before the movement. CONCLUSIONS: The motor perturbations observed in people with AMD in previous studies seem to result from difficulties in target identification rather than from visuomotor deficits.

Finding faces, animals, and vehicles in far peripheral vision.

Neuroimaging studies have shown that faces exhibit a central visual field bias, as compared to buildings and scenes. With a saccadic choice task, Crouzet, Kirchner, and Thorpe (2010) demonstrated a speed advantage for the detection of faces with stimuli located 8° from fixation. We used the same paradigm to examine whether the face advantage, relative to other categories (animals and vehicles), extends across the whole visual field (from 10° to 80° eccentricity) or whether it is limited to the central visual field. Pairs of photographs of natural scenes (a target and a distractor) were displayed simultaneously left and right of central fixation for 1s on a panoramic screen. Participants were asked to saccade to a target stimulus (faces, animals, or vehicles). The distractors were images corresponding to the two other categories. Eye movements were recorded with a head-mounted eye tracker. Only the first saccade was measured. Experiment 1 showed that (a) in terms of speed of categorization, faces maintain their advantage over animals and vehicles across the whole visual field, up to 80° and (b) even in crowded conditions (an object embedded in a scene), performance was above chance for the three categories of stimuli at 80° eccentricity. Experiment 2 showed that, when compared to another category with a high degree of within category structural similarity (cars), faces keep their advantage at all eccentricities. These results suggest that the bias for faces is not limited to the central visual field, at least in a categorization task.

Categorization Task over a Touch Screen in Age-Related Macular Degeneration.

PURPOSE: In our modern society, many touch screen applications require hand-eye coordination to associate an icon with its specific contextual unit on phones, on computers, or in public transport. We assessed the ability of patients with age-related macular degeneration (AMD) to explore scenes and to associate a target (animal or object) with a unique congruent scene (e.g., to match a fish with the sea) presented between three other distractors on a touch screen computer. METHODS: Twenty-four patients with AMD (64 to 90 years) with best-corrected visual acuity between 20/40 and 20/400 as well as 17 age-matched (60 to 94 years) and 15 young (22 to 34 years) participants with normal visual acuity had to match a target with a congruent scene by moving their index finger on a 22-in touch screen. RESULTS: Patients were as accurate (98.7% correct responses) as the age-matched control (98.9% correct responses) and young participants (99.3% correct responses) at performing the task. The duration of exploration was significantly longer for the AMD patients (mean, 4.13 seconds) compared with the age-matched group (mean, 2.96 seconds). The young participants were also significantly faster than the old group (mean, 0.93 seconds). The movement parameters of the older participants (patients and old control subjects) were affected compared with the young; the peak speed decreased (-8 cm/s) and the movement duration increased (+0.9 seconds) with age compared with the young group. CONCLUSIONS: People with AMD are able to perform a contextual association task on a touch screen with high accuracy. The AMD patients were specifically affected in the "exploration" phase; their accuracy and movement parameters did not differ from the old control group. Our study suggests that the decline associated with AMD is more focused on the duration of exploration than on movement parameters in touch screen use.

Conspiracy beliefs and perceptual inference in times of political uncertainty.

Sociopolitical crises causing uncertainty have accumulated in recent years, providing fertile ground for the emergence of conspiracy ideations. Computational models constitute valuable tools for understanding the mechanisms at play in the formation and rigidification of these unshakeable beliefs. Here, the Circular Inference model was used to capture associations between changes in perceptual inference and the dynamics of conspiracy ideations in times of uncertainty. A bistable perception task and conspiracy belief assessment focused on major sociopolitical events were administered to large populations from three polarized countries. We show that when uncertainty peaks, an overweighting of sensory information is associated with conspiracy ideations. Progressively, this exploration strategy gives way to an exploitation strategy in which increased adherence to conspiracy theories is associated with the amplification of prior information. Overall, the Circular Inference model sheds new light on the possible mechanisms underlying the progressive strengthening of conspiracy theories when individuals face highly uncertain situations.

A pilot study investigating affective forecasting biases with a novel virtual reality-based paradigm.

A body of research indicates that people are prone to overestimate the affective impact of future events. Here, we developed a novel experimental paradigm to study these affective forecasting biases under laboratory conditions using subjective (arousal and valence) and autonomic measures (skin conductance responses, SCRs, and heart rate). Thirty participants predicted their emotional responses to 15 unpleasant, 15 neutral, and 15 pleasant scenarios (affective forecasting phase) to which they were then exposed in virtual reality (emotional experience phase). Results showed that participants anticipated more extreme arousal and valence scores than they actually experienced for unpleasant and pleasant scenarios. The emotional experience phase was characterized by classic autonomic patterns, i.e., higher SCRs for emotionally arousing scenarios and greater peak cardiac acceleration for pleasant scenarios. During the affective forecasting phase, we found only a moderate association between arousal scores and SCRs and no valence-dependent modulation of cardiac activity. This paradigm opens up new perspectives for investigating affective forecasting abilities under lab-controlled conditions, notably in psychiatric disorders with anxious anticipations.

Spatial frequency processing and its modulation by emotional content in severe alcohol use disorder.

RATIONALE: Visuo-perceptive deficits in severe alcohol use disorder (SAUD) remain little understood, notably regarding the respective involvement of the two main human visual streams, i.e., magnocellular (MC) and parvocellular (PC) pathways, in these deficits. Besides, in healthy populations, low-level visual perception can adapt depending on the nature of visual cues, among which emotional features, but this MC and PC pathway adaptation to emotional content is unexplored in SAUD. OBJECTIVES: To assess MC and PC functioning as well as their emotional modulations in SAUD. METHODS: We used sensitivity indices (d') and repeated-measures analyses of variance to compare orientation judgments of Gabor patches sampled at various MC- and PC-related spatial frequencies in 35 individuals with SAUD and 38 matched healthy controls. We then explored how emotional content modulated performances by introducing neutral or fearful face cues immediately before the Gabor patches and added the type of cue in the analyses. RESULTS: SAUD patients showed a general reduction in sensitivity across all spatial frequencies, indicating impoverished processing of both coarse and fine-scale visual content. However, we observed selective impairments depending on facial cues: individuals with SAUD processed intermediate spatial frequencies less efficiently than healthy controls following neutral faces, whereas group differences emerged for the highest spatial frequencies following fearful faces. Altogether, SAUD was associated with mixed MC and PC deficits that may vary according to emotional content, in line with a flexible but suboptimal use of low-level visual content. Such subtle alterations could have implications for everyday life's complex visual judgments.

Decoding Activity in Broca's Area Predicts the Occurrence of Auditory Hallucinations Across Subjects.

BACKGROUND: Functional magnetic resonance imaging (fMRI) capture aims at detecting auditory-verbal hallucinations (AVHs) from continuously recorded brain activity. Establishing efficient capture methods with low computational cost that easily generalize between patients remains a key objective in precision psychiatry. To address this issue, we developed a novel automatized fMRI-capture procedure for AVHs in patients with schizophrenia (SCZ). METHODS: We used a previously validated but labor-intensive personalized fMRI-capture method to train a linear classifier using machine learning techniques. We benchmarked the performances of this classifier on 2320 AVH periods versus resting-state periods obtained from SCZ patients with frequent symptoms (n = 23). We characterized patterns of blood oxygen level-dependent activity that were predictive of AVH both within and between subjects. Generalizability was assessed with a second independent sample gathering 2000 AVH labels (n = 34 patients with SCZ), while specificity was tested with a nonclinical control sample performing an auditory imagery task (840 labels, n = 20). RESULTS: Our between-subject classifier achieved high decoding accuracy (area under the curve = 0.85) and discriminated AVH from rest and verbal imagery. Optimizing the parameters on the first schizophrenia dataset and testing its performance on the second dataset led to an out-of-sample area under the curve of 0.85 (0.88 for the converse test). We showed that AVH detection critically depends on local blood oxygen level-dependent activity patterns within Broca's area. CONCLUSIONS: Our results demonstrate that it is possible to reliably detect AVH states from fMRI blood oxygen level-dependent signals in patients with SCZ using a multivariate decoder without performing complex preprocessing steps. These findings constitute a crucial step toward brain-based treatments for severe drug-resistant hallucinations.

Visual abilities in Severe Alcohol Use Disorder: Preserved spatial but impaired temporal resolution.

Visuospatial impairments have long been reported in Severe Alcohol Use Disorder but remain poorly understood, notably regarding the involvement of magnocellular (MC) and parvocellular (PC) pathways. This empirical gap hampers the understanding of the implications of these visual changes, especially since the MC and PC pathways are thought to sustain central bottom-up and top-down processes during cognitive processing. They thus influence our ability to efficiently monitor our environment and make the most effective decisions. To overcome this limitation, we measured PC-inferred spatial and MC-inferred temporal resolution in 35 individuals with SAUD and 30 healthy controls. We used Landolt circles displaying small apertures outside the sensitivity range of MC cells or flickering at a temporal frequency exceeding PC sensitivity. We found evidence of preserved PC spatial resolution combined with impaired MC temporal resolution in SAUD. We also measured how spatial and temporal sensitivity is influenced by the prior presentation of fearful faces - as emotional content could favor MC processing over PC one - but found no evidence of emotional modulation in either group. This spatio-temporal dissociation implies that individuals with SAUD may process visual details efficiently but perceive rapidly updating visual information at a slower pace. This deficit has implications for the tracking of rapidly changing stimuli in experimental tasks, but also for the decoding of crucial everyday visual incentives such as faces, whose micro-expressions vary continuously. Future studies should further specify the visual profile of individuals with SAUD to incorporate disparate findings within a theoretically grounded model of vision.

Intrusive experiences in posttraumatic stress disorder: Treatment response induces changes in the directed functional connectivity of the anterior insula.

BACKGROUND: One of the core features of posttraumatic stress disorder (PTSD) is re-experiencing trauma. The anterior insula (AI) has been proposed to play a crucial role in these intrusive experiences. However, the dynamic function of the AI in re-experiencing trauma and its putative modulation by effective therapy need to be specified. METHODS: Thirty PTSD patients were enrolled and exposed to traumatic memory reactivation therapy. Resting-state functional magnetic resonance imaging (fMRI) scans were acquired before and after treatment. To explore AI-directed influences over the rest of the brain, we referred to a mixed model using pre-/posttreatment Granger causality analysis seeded on the AI as a within-subject factor and treatment response as a between-subject factor. To further identify correlates of re-experiencing trauma, we investigated how intrusive severity affected (i) causality maps and (ii) the spatial stability of other intrinsic brain networks. RESULTS: We observed changes in AI-directed functional connectivity patterns in PTSD patients. Many within- and between-network causal paths were found to be less influenced by the AI after effective therapy. Insular influences were found to be positively correlated with re-experiencing symptoms, while they were linked with a stronger default mode network (DMN) and more unstable central executive network (CEN) connectivity. CONCLUSION: We showed that directed changes in AI signaling to the DMN and CEN at rest may underlie the degree of re-experiencing symptoms in PTSD. A positive response to treatment further induced changes in network-to-network anticorrelated patterns. Such findings may guide targeted neuromodulation strategies in PTSD patients not suitably improved by conventional treatment.

Attentional bias towards negative stimuli in healthy individuals and the effects of trait anxiety.

This study aimed to investigate the time course of attentional bias for negative information in healthy individuals and to assess the associated influence of trait anxiety. Thirty-eight healthy volunteers performed an emotional dot-probe task with pairs of negative and neutral scenes, presented for either 1 or 2 s and followed by a target placed at the previous location of either negative or neutral stimulus. Analyses included eye movements during the presentation of the scenes and response times associated with target localization. In a second step, analyses focused on the influence of trait anxiety. While there was no significant difference at the behavioral level, the eye-tracking data revealed that negative information held longer attention than neutral stimuli once fixated. This initial maintenance bias towards negative pictures then increased with increasing trait anxiety. However, at later processing stages, only individuals with the highest trait anxiety appeared to fixate longer on negative pictures than neutral pictures, individuals with low trait anxiety showing the opposite pattern. This study provides novel evidence that healthy individuals display an attentional maintenance bias towards negative stimuli, which is associated with trait anxiety.

Attentional capture by incongruent object/background scenes in patients with Alzheimer disease.

AIM: Object/background association is critical to understand the context of visual scenes but also in daily life tasks like object search. Patients with Alzheimer disease (AD) exhibit impairment in scene processing at different levels: perception, recognition, memory and spatial navigation. We explored whether patients with AD make use of contextual information in congruent and incongruent target/background conditions in three different saccadic choice tasks. EXPERIMENT: We recruited 36 participants (12 young, 12 patients with AD at a moderate stage and 12 age-matched controls). Pairs of scenes (one congruent and one incongruent object/background) were displayed. In a free viewing task we recorded whether the participants spontaneously direct their gaze (eye tracker recordings) toward the congruent or the incongruent scene. In a task referred as "implicit", the participants had to saccade toward a pre-defined target (animal or piece of furniture) in a scene (congruent or not with the target). In a task, called "explicit", participants had to saccade towards the congruent scene. RESULTS: In contrast with both young and older controls patients with AD showed difficulties to refrain a first saccade toward incongruent scenes in the free viewing and the implicit tasks. They were at chance level in the explicit task. When given time to explore the two scenes, in a manual response condition, they were able to accomplish the implicit and explicit tasks with good accuracy. CONCLUSION: In contrast to healthy controls patients with AD exhibited a strong, significant, bias towards incongruent object/background scenes, even in the free viewing task, suggesting that unfamiliar or deviant stimuli attract their attention spontaneously. This result is in line with studies showing impairments in filtering out irrelevant distractors in visual search tasks and with studies suggesting inefficient top-down control to select relevant information at early stage of the disease.

Impact of age-related macular degeneration on object searches in realistic panoramic scenes.

BACKGROUND: This study investigated whether realistic immersive conditions with dynamic indoor scenes presented on a large, hemispheric panoramic screen covering 180° of the visual field improved the visual search abilities of participants with age-related macular degeneration (AMD). METHOD: Twenty-one participants with AMD, 16 age-matched controls and 16 young observers were included. Realistic indoor scenes were presented on a panoramic five metre diameter screen. Twelve different objects were used as targets. The participants were asked to search for a target object, shown on paper before each trial, within a room composed of various objects. A joystick was used for navigation within the scene views. A target object was present in 24 trials and absent in 24 trials. The percentage of correct detection of the target, the percentage of false alarms (that is, the detection of the target when it was absent), the number of scene views explored and the search time were measured. RESULTS: The search time was slower for participants with AMD than for the age-matched controls, who in turn were slower than the young participants. The participants with AMD were able to accomplish the task with a performance of 75 per cent correct detections. This was slightly lower than older controls (79.2 per cent) while young controls were at ceiling (91.7 per cent). Errors were mainly due to false alarms resulting from confusion between the target object and another object present in the scene in the target-absent trials. CONCLUSION: The outcomes of the present study indicate that, under realistic conditions, although slower than age-matched, normally sighted controls, participants with AMD were able to accomplish visual searches of objects with high accuracy.

Glaucoma Affects Viewing Distance for Recognition of Sex and Facial Expression.

Purpose: To measure the distance for sex and facial expression recognition in patients with glaucoma. Methods: Sixteen patients with open-angle glaucoma, 16 age-matched controls, and 12 young controls participated. During each trial, a face covering 0.36° × 0.5°, simulating the angular size of a face viewed at 20 m, was presented centrally. The angular size increased automatically by steps of 5 cm, simulating the face moving progressively closer. The participants were asked to stop the progression with a keypress, first, when they were able to recognize the sex, and second, when they were able to recognize the facial expression (angry, happy, neutral). We measured the threshold equivalent viewing distance to recognize the sex and the facial expression. Results: Participants with glaucoma, both those with and without reduced central acuity, required a shorter viewing distance (i.e., a larger face) than did controls to recognize both the sex (by 2.59 m, F1,30 = 8.7, P < 0.006) and the facial expression (by 3.64 m, F1,30 = 14, P < 0.001). No significant difference was found between younger and older controls. Conclusions: Face perception is a skill that is reliant on central vision. Our behavioral results are consistent with the hypothesis of reduced central sensitivity in glaucoma. We suggest that the necessity to view larger faces in patients might result from a higher sensitivity to crowding that increases the difficulty to perceive the relevant features for recognition of both sex and facial expressions, akin to normal peripheral vision.

Functional Synergy Between Postural and Visual Behaviors When Performing a Difficult Precise Visual Task in Upright Stance.

Previous works usually report greater postural stability in precise visual tasks (e.g., gaze-shift tasks) than in stationary-gaze tasks. However, existing cognitive models do not fully support these results as they assume that performing an attention-demanding task while standing would alter postural stability because of the competition of attention between the tasks. Contrary to these cognitive models, attentional resources may increase to create a synergy between visual and postural brain processes to perform precise oculomotor behaviors. To test this hypothesis, we investigated a difficult searching task and a control free-viewing task. The precise visual task required the 16 young participants to find a target in densely furnished images. The free-viewing task consisted of looking at similar images without searching anything. As expected, the participants exhibited significantly lower body displacements (linear, angular) and a significantly higher cognitive workload in the precise visual task than in the free-viewing task. Most important, our exploration showed functional synergies between visual and postural processes in the searching task, that is, significant negative relationships showing lower head and neck displacements to reach more expended zones of fixation. These functional synergies seemed to involve a greater attentional demand because they were not significant anymore when the cognitive workload was controlled (partial correlations). In the free-viewing task, only significant positive relationships were found and they did not involve any change in cognitive workload. An alternative cognitive model and its potential subtended neuroscientific circuit are proposed to explain the supposedly cognitively grounded functional nature of vision-posture synergies in precise visual tasks.

The Stationary-Gaze Task Should Not Be Systematically Used as the Control Task in Studies of Postural Control.

In studies of postural control, a control task is often used to understand significant effects obtained with experimental manipulations. This task should be the easiest task and (therefore) engage the lowest behavioral variability and cognitive workload. Since 1983, the stationary-gaze task is considered as the most relevant control task. Instead, the authors expected that free looking at small targets (white paper or images; visual angle: 12°) could be an easier task. To verify this assumption, 16 young individuals performed stationary-gaze, white-panel, and free-viewing 12° tasks in steady and relaxed stances. The stationary-gaze task led to significantly higher cognitive workload (mean score in the National Aeronotics and Space Administration Task Load Index questionnaire), higher interindividual body (head, neck, and lower back) linear variability, and higher interindividual body angular variability-not systematically yet-than both other tasks. There was more cognitive workload in steady than relaxed stances. The authors also tested if a free-viewing 24° task could lead to greater angular displacement, and hence greater body sway, than could the other tasks in relaxed stance. Unexpectedly, the participants mostly moved their eyes and not their body in this task. In the discussion, the authors explain why the stationary-gaze task may not be an ideal control task and how to choose this neutral task.

Levodopa has primarily negative influences on postural control in patients with Parkinson's disease.

Patients with Parkinson's disease have better functional status and motor performance under on-drug conditions. However, the administration of levodopa leads to greater postural sway. The present study's primary objective was to determine whether this on-drug problem may be related to a lack of adjustment in postural control mechanisms and body segment rotations. Fourteen patients with Parkinson's disease and 14 controls performed two gaze-shift tasks (40° to the left and 40° to the right, at 0.125 and 0.25Hz) and a stationary gaze task in two sessions (an off-drug session and an on-drug session for the patients, and two off-drug sessions for the controls). At baseline, the "on-drug" patients indeed swayed significantly more than the controls during the gaze-shift tasks. As expected, acute L-dopa administration did not increase eye, head, neck and lower back rotation of the patients during the gaze-shift tasks. Unexpectedly, levodopa appeared to enable the patients to significantly increase the contribution of their postural control mechanisms (relative to controls) during the gaze-shift tasks. However, and as expected, this adjustment was not great enough to enable the patients to maintain their postural sway as well as the controls did. Overall, the administration of levodopa seemed to destabilize the patients - especially with regard to the lower back region. In addition, the patients used hypermetric eye rotations during the gaze-shift tasks under both off- and on-drug conditions. If they had not used these compensatory eye rotations, their unsafe behavior at the hip level might have been even more pronounced. Future research should focus on this lower back weakness.

Explicit and implicit emotional processing in peripheral vision: A saccadic choice paradigm.

We investigated explicit and implicit emotional processing in peripheral vision using saccadic choice tasks. Emotional-neutral pairs of scenes were presented peripherally either at 10, 30 or 60° away from fixation. The participants had to make a saccadic eye movement to the target scene: emotional vs neutral in the explicit task, and oval vs rectangular in the implicit task. In the explicit task, pleasant scenes were reliably categorized as emotional up to 60° while performance for unpleasant scenes decreased between 10° and 30° and did not differ from chance at 60°. Categorization of neutral scenes did not differ from chance. Performance in the implicit task was significantly better for emotional targets than for neutral targets at 10° and this beneficial effect of emotion persisted only for pleasant scenes at 30°. Thus, these findings show that explicit and implicit emotional processing in peripheral vision depends on eccentricity and valence of stimuli.