Detection of emotional faces: The role of spatial frequencies and local features.

Models of emotion processing suggest that threat-related stimuli such as fearful faces can be detected based on the rapid extraction of low spatial frequencies. However, this remains debated as other models argue that the decoding of facial expressions occurs with a more flexible use of spatial frequencies. The purpose of this study was to clarify the role of spatial frequencies and differences in luminance contrast between spatial frequencies, on the detection of facial emotions. We used a saccadic choice task in which emotional-neutral face pairs were presented and participants were asked to make a saccade toward the neutral or the emotional (happy or fearful) face. Faces were displayed either in low, high, or broad spatial frequencies. Results showed that participants were better to saccade toward the emotional face. They were also better for high or broad than low spatial frequencies, and the accuracy was higher with a happy target. An analysis of the eye and mouth saliency ofour stimuli revealed that the mouth saliency of the target correlates with participants' performance. Overall, this study underlines the importance of local more than global information, and of the saliency of the mouth region in the detection of emotional and neutral faces.

Does alcohol automatically capture drinkers' attention? Exploration through an eye-tracking saccadic choice task.

RATIONALE: Dominant theoretical models postulate the presence of an automatic attentional bias (AB) towards alcohol-related stimuli in alcohol use disorder, such AB constituting a core feature of this disorder. An early alcohol AB has been documented in subclinical populations such as binge drinking (i.e., a drinking pattern prevalent in youth and characterized by repeated alternation between alcohol intoxications and withdrawals, generating cerebral consequences). However, the automatic nature of AB remains to be established. OBJECTIVES: We investigated the automatic nature of AB in binge drinkers through the saccadic choice task. This eye-tracking paradigm consistently highlights the extremely fast and involuntary saccadic responses elicited by faces in humans, relative to other object categories. Through an alcohol-related adaptation of the saccadic choice task, we tested whether the early and automatic capture of attentional resources elicited by faces can also be found for alcohol-related stimuli in binge drinkers, as predicted by theoretical models. METHODS: Forty-three binge drinkers and 44 control participants performed two versions of the saccadic choice task. In the original version, two images (a face, a vehicle) were displayed on the left and right side of the screen respectively. Participants had to perform a saccade as fast as possible towards the target stimulus (either face or vehicle). In the alcohol-related version, the task was identical, but the images were an alcoholic beverage and a non-alcoholic stimulus. RESULTS: We replicated the automatic attraction towards faces in both groups, as faces generated higher saccadic accuracy, speed, and amplitude than vehicles, as well as higher corrective saccade proportion. Concerning the alcohol-related adaptation of the task, groups did not differ for the accuracy, speed, and amplitude of the first saccade towards alcohol. However, binge drinkers differed from controls regarding the proportion of corrective saccade towards non-alcoholic stimuli after an error saccade towards alcohol, suggesting the presence of an alcohol disengagement bias specific to binge drinkers. CONCLUSIONS: Alcohol-related AB in binge drinkers is not characterized by an early and automatic hijacking of attention towards alcohol. This AB rather relies on later and more controlled processing stages, namely a difficulty to disengage attentional resources from alcohol-related stimuli.

Spatio-temporal attention toward emotional scenes across adulthood.

Research on emotion suggests that the attentional preference observed toward the negative stimuli in young adults tends to disappear in normal aging and, sometimes, to shift toward a preference for positive stimuli. The current eye-tracking study investigated visual exploration of paired natural scenes of different valence (Negative-Neutral, Positive-Neutral, and Negative-Positive pairs) in three age groups (young, middle-aged, and older adults). Two arousal levels of stimuli (high and low arousal) were also considered given role of this factor in age-related effects on emotion. Results showed the automatic attentional orienting toward the negative stimuli was relatively preserved in our three age groups although reduced in the elderly, in both arousal conditions. A similar negativity bias was also observed in initial attention focusing but shifted toward a positivity bias over time in the three age groups. Moreover, it appeared the spatial exploration of emotional scenes evolved over time differently for older adults compared with other age groups. No difference between young adults and middle-aged adults in ocular behavior was observed. This study confirms the interest of studying both spatial and temporal characteristics of oculomotor behaviors to better understand the age-related effects on emotion. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Synchronization of acquisition devices in neuroimaging: An application using co-registration of eye movements and electroencephalography.

Interest in applications for the simultaneous acquisition of data from different devices is growing. In neuroscience for example, co-registration complements and overcomes some of the shortcomings of individual methods. However, precise synchronization of the different data streams involved is required before joint data analysis. Our article presents and evaluates a synchronization method which maximizes the alignment of information across time. Synchronization through common triggers is widely used in all existing methods, because it is very simple and effective. However, this solution has been found to fail in certain practical situations, namely for the spurious detection of triggers and/or when the timestamps of triggers sampled by each acquisition device are not jointly distributed linearly for the entire duration of an experiment. We propose two additional mechanisms, the "Longest Common Subsequence" algorithm and a piecewise linear regression, in order to overcome the limitations of the classical method of synchronizing common triggers. The proposed synchronization method was evaluated using both real and artificial data. Co-registrations of electroencephalographic signals (EEG) and eye movements were used for real data. We compared the effectiveness of our method to another open source method implemented using EYE-EEG toolbox. Overall, we show that our method, implemented in C++ as a DOS application, is very fast, robust and fully automatic.

The Role of Emotional Content and Perceptual Saliency During the Programming of Saccades Toward Faces.

Previous studies have shown that the human visual system can detect a face and elicit a saccadic eye movement toward it very efficiently compared to other categories of visual stimuli. In the first experiment, we tested the influence of facial expressions on fast face detection using a saccadic choice task. Face-vehicle pairs were simultaneously presented and participants were asked to saccade toward the target (the face or the vehicle). We observed that saccades toward faces were initiated faster, and more often in the correct direction, than saccades toward vehicles, regardless of the facial expressions (happy, fearful, or neutral). We also observed that saccade endpoints on face images were lower when the face was happy and higher when it was neutral. In the second experiment, we explicitly tested the detection of facial expressions. We used a saccadic choice task with emotional-neutral pairs of faces and participants were asked to saccade toward the emotional (happy or fearful) or the neutral face. Participants were faster when they were asked to saccade toward the emotional face. They also made fewer errors, especially when the emotional face was happy. Using computational modeling, we showed that this happy face advantage can, at least partly, be explained by perceptual factors. Also, saccade endpoints were lower when the target was happy than when it was fearful. Overall, we suggest that there is no automatic prioritization of emotional faces, at least for saccades with short latencies, but that salient local face features can automatically attract attention.

Isolated face features are sufficient to elicit ultra-rapid and involuntary orienting responses toward faces.

Previous studies have shown that face stimuli influence the programming of eye movements by eliciting involuntary and extremely fast saccades toward them. The present study examined whether holistic processing of faces mediates these effects. We used a saccadic choice task in which participants were presented simultaneously with two images and had to perform a saccade toward the one containing a target stimulus (e.g., a face). Across three experiments, stimuli were altered via upside-down inversion (Experiment 1) or scrambling of thumbnails within the images (Experiments 2 and 3) in order to disrupt holistic processing. We found that disruption of holistic processing only had a limited impact on the latency of saccades toward face targets, which remained extremely short (minimum saccadic reaction times of only ∼120-130 ms), and did not affect the proportion of error saccades toward face distractors that captured attention more than other distractor categories. It, however, resulted in increasing error rate of saccades toward face targets. These results suggest that the processing of isolated face features is sufficient to elicit extremely fast and involuntary saccadic responses toward them. Holistic representations of faces may, however, be used as a search template to accurately detect faces.

Influence of peripheral vision on object categorization in central vision.

Predictive models of visual recognition state that predictions based on the rapid processing of low spatial frequencies (LSF) may guide the subsequent processing of high spatial frequencies (HSF). While the HSF signal necessarily comes from central vision, most of the LSF signal comes from peripheral vision. The present study aimed at understanding how LSF in peripheral vision may be used to generate predictive signals that guide visual processes in central vision. In two experiments, participants performed an object categorization task in central vision while a semantically congruent or incongruent scene background was displayed in peripheral vision. In Experiment 1, results showed a congruence effect when the peripheral scene was displayed before the object onset. In Experiment 2, results showed a congruence effect only when the peripheral scene was intact, thus carrying a semantic meaning, but not when it was phase-scrambled, thus carrying only low-level information. The study suggests that the low resolution of peripheral vision facilitates the processing of foveated objects in the visual scene, in line with predictive models of visual recognition.

Twice-daily neuronavigated intermittent theta burst stimulation for bipolar depression: A Randomized Sham-Controlled Pilot Study.

The safety and efficacy of neuronavigated intermittent theta burst stimulation (iTBS) in patients with bipolar depression has not yet been investigated. We hypothesized the superiority of active iTBS over sham. Twenty-six patients were randomly allocated to receive either active (n=12) or sham (n=14) iTBS. Response and remission rates according to changes in depression MADRS score were high following active iTBS (72% and 42% for response and remission rates, respectively), but no significant difference was found after sham stimulation (42%and 25%). No adverse events were observed. This study revealed the safety and tolerability of twice daily iTBS in patients with bipolar depression. Larger controlled studies are warranted to prove iTBS superiority in treatment-resistant bipolar depression.

Color improves edge classification in human vision.

Despite the complexity of the visual world, humans rarely confuse variations in illumination, for example shadows, from variations in material properties, such as paint or stain. This ability to distinguish illumination from material edges is crucial for determining the spatial layout of objects and surfaces in natural scenes. In this study, we explore the role that color (chromatic) cues play in edge classification. We conducted a psychophysical experiment that required subjects to classify edges into illumination and material, in patches taken from images of natural scenes that either contained or did not contain color information. The edge images were of various sizes and were pre-classified into illumination and material, based on inspection of the edge in the context of the whole image from which the edge was extracted. Edge classification performance was found to be superior for the color compared to grayscale images, in keeping with color acting as a cue for edge classification. We defined machine observers sensitive to simple image properties and found that they too classified the edges better with color information, although they failed to capture the effect of image size observed in the psychophysical experiment. Our findings are consistent with previous work suggesting that color information facilitates the identification of material properties, transparency, shadows and the perception of shape-from-shading.

Face perception influences the programming of eye movements.

Previous studies have shown that face stimuli elicit extremely fast and involuntary saccadic responses toward them, relative to other categories of visual stimuli. In the present study, we further investigated to what extent face stimuli influence the programming and execution of saccades examining their amplitude. We performed two experiments using a saccadic choice task: two images (one with a face, one with a vehicle) were simultaneously displayed in the left and right visual fields of participants who had to initiate a saccade toward the image (Experiment 1) or toward a cross in the image (Experiment 2) containing a target stimulus (a face or a vehicle). Results revealed shorter saccades toward vehicle than face targets, even if participants were explicitly asked to perform their saccades toward a specific location (Experiment 2). Furthermore, error saccades had smaller amplitude than correct saccades. Further analyses showed that error saccades were interrupted in mid-flight to initiate a concurrently-programmed corrective saccade. Overall, these data suggest that the content of visual stimuli can influence the programming of saccade amplitude, and that efficient online correction of saccades can be performed during the saccadic choice task.

The importance of recurrent top-down synaptic connections for the anticipation of dynamic emotions.

Different studies have shown the efficiency of a feed-forward neural network in categorizing basic emotional facial expressions. However, recent findings in psychology and cognitive neuroscience suggest that visual recognition is not a pure bottom-up process but likely involves top-down recurrent connectivity. In the present computational study, we compared the performances of a pure bottom-up neural network (a standard multi-layer perceptron, MLP) with a neural network involving recurrent top-down connections (a simple recurrent network, SRN) in the anticipation of emotional expressions. In two complementary simulations, results revealed that the SRN outperformed the MLP for ambiguous intensities in the temporal sequence, when the emotions were not fully depicted but when sufficient contextual information (related to previous time frames) was provided. Taken together, these results suggest that, despite the cost of recurrent connections in terms of energy and processing time for biological organisms, they can provide a substantial advantage for the fast recognition of uncertain visual signals.

Early Emotional Attention is Impacted in Alzheimer's Disease: An Eye-Tracking Study.

Emotional deficits have been repetitively reported in Alzheimer's disease (AD) without clearly identifying how emotional processing is impaired in this pathology. This paper describes an investigation of early emotional processing, as measured by the effects of emotional visual stimuli on a saccadic task involving both pro (PS) and anti (AS) saccades. Sixteen patients with AD and 25 age-matched healthy controls were eye-tracked while they had to quickly move their gaze toward a positive, negative, or neutral image presented on a computer screen (in the PS condition) or away from the image (in the AS condition). The age-matched controls made more AS mistakes for negative stimuli than for other stimuli, and triggered PSs toward negative stimuli more quickly than toward other stimuli. In contrast, patients with AD showed no difference with regard to the emotional category in any of the tasks. The present study is the first to highlight a lack of early emotional attention in patients with AD. These results should be taken into account in the care provided to patients with AD, since this early impairment might seriously degrade their overall emotional functioning.

Scene and human face recognition in the central vision of patients with glaucoma.

Primary open-angle glaucoma (POAG) firstly mainly affects peripheral vision. Current behavioral studies support the idea that visual defects of patients with POAG extend into parts of the central visual field classified as normal by static automated perimetry analysis. This is particularly true for visual tasks involving processes of a higher level than mere detection. The purpose of this study was to assess visual abilities of POAG patients in central vision. Patients were assigned to two groups following a visual field examination (Humphrey 24-2 SITA-Standard test). Patients with both peripheral and central defects and patients with peripheral but no central defect, as well as age-matched controls, participated in the experiment. All participants had to perform two visual tasks where low-contrast stimuli were presented in the central 6° of the visual field. A categorization task of scene images and human face images assessed high-level visual recognition abilities. In contrast, a detection task using the same stimuli assessed low-level visual function. The difference in performance between detection and categorization revealed the cost of high-level visual processing. Compared to controls, patients with a central visual defect showed a deficit in both detection and categorization of all low-contrast images. This is consistent with the abnormal retinal sensitivity as assessed by perimetry. However, the deficit was greater for categorization than detection. Patients without a central defect showed similar performances to the controls concerning the detection and categorization of faces. However, while the detection of scene images was well-maintained, these patients showed a deficit in their categorization. This suggests that the simple loss of peripheral vision could be detrimental to scene recognition, even when the information is displayed in central vision. This study revealed subtle defects in the central visual field of POAG patients that cannot be predicted by static automated perimetry assessment using Humphrey 24-2 SITA-Standard test.

Do low spatial frequencies explain the extremely fast saccades towards human faces?

The visual perception of human faces by man is fast and efficient compared to that of other categories of objects. Using a saccadic choice task, recent studies showed that participants were able to initiate fast reliable saccades in just 100-110ms toward an image of a human face, when this was presented alongside another image without a face. This extremely fast saccadic reaction time is barely predicted using classical models of visual perception. Thus, the present research investigates whether this result might be explained by the low spatial frequency content of images. Using the same paradigm, with two images simultaneously presented to the left or right visual fields, participants were asked to make a saccade towards a target image. The target was defined as an image belonging to one category: human face, animal or vehicle. The other image corresponded to the distractor and belongs to the other categories. We compared performance to saccade toward one category of target. The two images were displayed either in color, gray-level, low-pass filtered or high-pass filtered. As previous studies, we found that the shortest SRT was observed for saccades towards faces rather than towards animals or vehicles. Analysis of saccadic reaction time distributions showed that, in 130-140ms, participants were able to make more correct than incorrect saccades towards faces for unfiltered (color and gray-level) and low-pass filtered images whereas they needed more time for high-pass filtered images. In contrast, the minimum time participants needed to correctly saccade towards animals and vehicles was longer for low-pass and high-pass filtered than for unfiltered images. The analysis of the image statistics in the Fourier domain revealed that the amplitude spectrum of faces was mainly contained in the low spatial frequencies. Consistent with a coarse-to-fine processing of visual information, our results suggest that extremely fast saccades towards faces could be initiated by low spatial frequencies.

How a distractor influences fixations during the exploration of natural scenes.

The distractor effect is a well-established means of studying different aspects of fixation programming during the exploration of visual scenes. In this study, we present a taskirrelevant distractor to participants during the free exploration of natural scenes. We investigate the control and programming of fixations by analyzing fixation durations and locations, and the link between the two. We also propose a simple mixture model evaluated using the Expectation-Maximization algorithm to test the distractor effect on fixation locations, including fixations which did not land on the distractor. The model allows us to quantify the influence of a visual distractor on fixation location relative to scene saliency for all fixations, at distractor onset and during all subsequent exploration. The distractor effect is not just limited to the current fixation, it continues to influence fixations during subsequent exploration. An abrupt change in the stimulus not only increases the duration of the current fixation, it also influences the location of the fixation which occurs immediately afterwards and to some extent, in function of the length of the change, the duration and location of any subsequent fixations. Overall, results from the eye movement analysis and the statistical model suggest that fixation durations and locations are both controlled by direct and indirect mechanisms.

An eye fixation-related potentials analysis of the P300 potential for fixations onto a target object when exploring natural scenes.

The P300 event-related potential has been extensively studied in electroencephalography with classical paradigms that force observers to not move their eyes. This potential is classically used to infer whether a target or a task-relevant stimulus was presented. Few researches have studied this potential through more ecological paradigms where observers were able to move their eyes. In this study, we examined with an ecological paradigm and an adapted methodology the P300 potential using a visual search task that involves eye movements to actively explore natural scenes and during which eye movements and electroencephalographic activity were coregistered. Averaging the electroencephalography signal time-locked to fixation onsets, a P300 potential was observed for fixations onto the target object but not for other fixations recorded for the same visual search or for fixations recorded during the free viewing without any task. Our approach consists of using control experimental conditions with similar eye movements to ensure that the P300 potential was attributable to the fact that the observer gazed at the target rather than to other factors such as eye movement pattern (the size of the previous saccade) or the "overlap issue" between the potentials elicited by two successive fixations. We also proposed to model the time overlap issue of the potentials elicited by consecutive fixations with various durations. Our results show that the P300 potential can be studied in ecological situations without any constraint on the type of visual exploration, with some precautions in the interpretation of results due to the overlap issue.

Dose intensity and toxicity associated with Taxotere formulation: a retrospective study in a population of breast cancer patients treated with docetaxel as an adjuvant or neoadjuvant chemotherapy.

Docetaxel is an antineoplastic drug from the taxane family that inhibits tubulin polymerization. Its brand name is Taxotere. In mid-2010, the formulation of Taxotere changed from a two-vial preparation needing a predilution (T2V) to a one-vial ready-to-use preparation (T1V). The aim of this study was to compare the toxicity profile of these two formulations. This retrospective observational and monocentric study included all patients who received Taxotere-based chemotherapy (100 mg/m) as an adjuvant or a neoadjuvant treatment for localized breast cancer, following initial treatment with anthracycline-based chemotherapy. Patients received either T2V or T1V Taxotere depending on the period of treatment. The main endpoint was the ratio of the dose of Taxotere received to that scheduled (R=docetaxel dose received/docetaxel dose scheduled). The secondary endpoint was tolerance. A total of 97 patients were included: 39 in the T2V group and 58 in the T1V group. The ratio of docetaxel received/docetaxel scheduled was significantly lower in the T1V than in the T2V group (0.83 vs. 0.95, respectively; P=0.028). A higher proportion of patients did not receive the totality of the scheduled dose in the T1V than in the T2V group (28 vs. 8%, respectively; P=0.03). Furthermore, the proportion of patients experiencing cutaneous toxicity was significantly higher in the T1V than in the T2V group (50 vs. 15%, respectively; P<0.001) as well as for neurological toxicity (31 vs. 15%, respectively; P=0.03). The frequency of grade 3 toxicities was higher in the T1V than in the T2V group (50 vs. 8%, P=0.016). The frequency of idiosyncratic toxicities was not affected by the change of formulation (4.7 vs. 5.4%, P=0.98). This study shows that patients treated with the T1V formulation received a significantly smaller dose of Taxotere than patients treated with T2V. In this small retrospective study, no conclusions can be drawn as to why a change in formulation would be associated with differences in dose tolerance. However, it does encourage caution and need for clinical data analysis when adopting even minor changes in the formulation of well-known anticancer drugs.

The Neural Bases of the Semantic Interference of Spatial Frequency-based Information in Scenes.

Current models of visual perception suggest that during scene categorization, low spatial frequencies (LSF) are processed rapidly and activate plausible interpretations of visual input. This coarse analysis would then be used to guide subsequent processing of high spatial frequencies (HSF). The present fMRI study examined how processing of LSF may influence that of HSF by investigating the neural bases of the semantic interference effect. We used hybrid scenes as stimuli by combining LSF and HSF from two different scenes, and participants had to categorize the HSF scene. Categorization was impaired when LSF and HSF scenes were semantically dissimilar, suggesting that the LSF scene was processed automatically and interfered with categorization of the HSF scene. fMRI results revealed that this semantic interference effect was associated with increased activation in the inferior frontal gyrus, the superior parietal lobules, and the fusiform and parahippocampal gyri. Furthermore, a connectivity analysis (psychophysiological interaction) revealed that the semantic interference effect resulted in increasing connectivity between the right fusiform and the right inferior frontal gyri. Results support influential models suggesting that, during scene categorization, LSF information is processed rapidly in the pFC and activates plausible interpretations of the scene category. These coarse predictions would then initiate top-down influences on recognition-related areas of the inferotemporal cortex, and these could interfere with the categorization of HSF information in case of semantic dissimilarity to LSF.

Spatial frequency processing in scene-selective cortical regions.

Visual analysis begins with the parallel extraction of different attributes at different spatial frequencies. Low spatial frequencies (LSF) convey coarse information and are characterized by high luminance contrast, while high spatial frequencies (HSF) convey fine details and are characterized by low luminance contrast. In the present fMRI study, we examined how scene-selective regions-the parahippocampal place area (PPA), the retrosplenial cortex (RSC) and the occipital place area (OPA)-responded to spatial frequencies when contrast was either equalized or not equalized across spatial frequencies. Participants performed a categorization task on LSF, HSF and non-filtered scenes belonging to two different categories (indoors and outdoors). We either left contrast across scenes untouched, or equalized it using a root-mean-square contrast normalization. We found that when contrast remained unmodified, LSF and NF scenes elicited greater activation than HSF scenes in the PPA. However, when contrast was equalized across spatial frequencies, the PPA was selective to HFS. This suggests that PPA activity relies on an interaction between spatial frequency and contrast in scenes. In the RSC, LSF and NF elicited greater response than HSF scenes when contrast was not modified, while no effect of spatial frequencies appeared when contrast was equalized across filtered scenes, suggesting that the RSC is sensitive to high-contrast information. Finally, we observed selective activation of the OPA in response to HSF, irrespective of contrast manipulation. These results provide new insights into how scene-selective areas operate during scene processing.

Rapid scene categorization: role of spatial frequency order, accumulation mode and luminance contrast.

Visual analysis follows a default, predominantly coarse-to-fine processing sequence. Low spatial frequencies (LSF) are processed more rapidly than high spatial frequencies (HSF), allowing an initial coarse parsing of visual input, prior to analysis of finer information. Our study investigated the influence of spatial frequency processing order, accumulation mode (i.e. how spatial frequency information is received as an input by the visual system, throughout processing), and differences in luminance contrast between spatial frequencies on rapid scene categorization. In Experiment 1, we used sequences composed of six filtered scenes, assembled from LSF to HSF (coarse-to-fine) or from HSF to LSF (fine-to-coarse) to test the effects of spatial frequency order. Spatial frequencies were either successive or additive within sequences to test the effects of spatial frequency accumulation mode. Results showed that participants categorized coarse-to-fine sequences more rapidly than fine-to-coarse sequences, irrespective of spatial frequency accumulation in the sequences. In Experiment 2, we investigated the extent to which differences in luminance contrast rather than in spatial frequency account for the advantage of coarse-to-fine over fine-to-coarse processing. Results showed that both spatial frequencies and luminance contrast account for a predominant coarse-to-fine processing, but that the coarse-to-fine advantage stems mainly from differences in spatial frequencies. Our study cautions against the use of contrast normalization in studies investigating spatial frequency processing. We argue that this type of experimental manipulation can impair the intrinsic properties of a visual stimulus. As the visual system relies on these to enable recognition, bias may be induced in strategies of visual analysis.