Trust at first sight: evidence from ERPs

Independent effects of working memory loads and facial expressions on event-related potential (ERP) responses: Evidence from mass univariate analysis.

Rapid and accurate processing of potential social threats is paramount to social thriving, and provides a clear evolutionary advantage. Though automatic processing of facial expressions has been assumed for some time, some researchers now question the extent to which this is the case. Here, we provide electrophysiological data from a psychological refractory period (PRP) dual-task paradigm in which participants had to decide whether a target face exhibited a neutral or fearful expression, as overlap with a concurrent auditory tone categorization task was experimentally manipulated. Specifically, we focused on four event-related potentials (ERP) linked to emotional face processing, covering distinct processing stages and topography: the early posterior negativity (EPN), early frontal positivity (EFP), late positive potential (LPP), and also the face-sensitive N170. As expected, there was an emotion modulation of each ERP. Most importantly, there was a significant attenuation of this emotional response proportional to the degree of task overlap for each component, except the N170. In fact, when the central overlap was greatest, this emotion-specific amplitude was statistically null for the EFP and LPP, and only marginally different from zero for the EPN. N170 emotion modulation was, on the other hand, unaffected by central overlap. Thus, our results show that emotion-specific ERPs for three out of four processing stages—i.e., perceptual encoding (EPN), emotion detection (EFP), or content evaluation (LPP)—are attenuated and even eliminated by central resource scarcity. Models assuming automatic processing should be revised to account for these results.

Visual tuning for words vs. symbol strings yields complementary increases of fast occipito-temporal activity (N1 or N170) in the event-related potential (ERP), and posterior-anterior gradients of increasing word-specific activity with functional magnetic resonance imaging (fMRI) in the visual word form system (VWFS). However, correlation of these coarse ERP and fMRI tuning responses seems limited to the most anterior part of the VWFS in adult and adolescent readers (Brem et al. [ 2006]: Neuroimage 29:822-837). We thus focused on fMRI tuning gradients of young readers with their more pronounced ERP print tuning, and compared developmental aspects of ERP and fMRI response tuning in the VWFS. Children (10.3 y, n = 19), adolescents (16.2 y, n = 13) and adults (25.2 y, n = 18) were tested with the same implicit reading paradigm using counterbalanced ERP and fMRI imaging. The word-specific occipito-temporal N1 specialization, its corresponding source activity, as well as the integrated source activity (0-700 ms) were most prominent in children and showed a marked decrease with age. The posterior-anterior fMRI gradient of word-specific activity instead which was fully established in children did not develop further, but exhibited a dependence on reading skills independent of age. To conclude, prominent developmental dissociation of the ERP and fMRI tuning patterns emerged despite convergent VWFS localization. The ERP response may selectively reflect fast visual aspects of print specialization, which become less important with age, while the fMRI response seems dominated by integrated task- and reading-related activations in the same regions.

Previous research has suggested that the perception of emotional images may also activate brain regions related to the preparation of motoric plans. However, little research has investigated whether these emotion-movement interactions occur at early or later stages of visual perception. In the current research, event-related potentials (ERPs) were used to examine the time course of the independent – and combined – effects of perceiving emotions and implied movement. Twenty-five participants viewed images from four categories: 1) emotional with implied movement, 2) emotional with no implied movement, 3) neutral with implied movement, and 4) neutral with no implied movement. Both emotional stimuli and movement-related stimuli led to larger N200 (200–300 ms) waveforms. Furthermore, at frontal sites, there was a marginal interaction between emotion and implied movement, such that negative stimuli showed greater N200 amplitudes vs. neutral stimuli, but only for images with implied movement. At posterior sites, a similar effect was observed for images without implied movement. The late positive potential (LPP; 500–1000 ms) was significant for emotion (at frontal sites) and movement (at frontal, central, and posterior sites), as well as for their interaction (at parietal sites), with larger LPPs for negative vs. neutral images with movement only. Together, these results suggest that the perception of emotion and movement interact at later stages of visual perception.

Effects of emotional intensity under perceptual load: An event-related potentials (ERPs) study

We tested the effect of different intensities of acute exercise on hunger, and post-exercise energy intake, and neurophysiological measures of attention towards food- and non-food stimuli in women. In a within-subjects crossover design, forty-two women completed no exercise, moderate-intensity exercise, and vigorous-intensity exercise sessions separated by one week, in a counterbalanced fashion. At each session, participants completed a passive viewing task of food (high- and low-calorie) and non-food pictures while electroencephalogram (EEG) data were recorded. The early posterior negativity (EPN), P3, and late positive potential (LPP) components of the event-related potential (ERP) measured neurophysiological responses. Subjective ratings of hunger were measured before and immediately after each condition using a visual analog scale (VAS) and food intake was measured using an ad libitum snack buffet offered at the end of each condition. Results indicated that hunger levels increased as time passed for all sessions. EPN amplitude was larger to non-food compared to food images; P3 amplitude was larger to food than non-food stimuli. LPP amplitude did not differ by high-calorie, low-calorie, or non-food images. Notably, there were no significant main effects or interactions of any ERP component amplitude as a function of exercise intensity. Food intake also did not differ by rest or moderate or vigorous exercise, although subjective arousal ratings to the images were higher after moderate and vigorous exercise compared to rest. Food images also had higher arousal and valence ratings than non-food images overall. Findings indicate that, in this sample, acute moderate and vigorous exercise compared to rest did not disproportionately affect neurophysiological measures of attention to food or non-food stimuli, caloric intake, or hunger.

Background: The abnormal cognitive processing of drug cues is a core characteristic of drug dependence. Previous research has suggested that the late positive potential (LPP) of heroin users is increased by heroin-related stimuli because of the attention-grabbing nature of such stimuli. Objectives: The present research used a modified emotional Stroop (eStroop) task to examine whether there was an early posterior negativity (EPN) modulation to heroin cues compared with emotional or neutral stimuli in heroin dependent subjects. Methods: Fifteen former heroin users and 15 matched controls performed the eStroop task, which was composed of positive, negative, heroin-related, and neutral pictures with superimposed color squares. Participants responded to the color of the square and not to the picture while behavioral data and event-related potentials were recorded. Results: There were no significant differences of EPN amplitudes to emotional and neutral stimuli between heroin users and controls. However, heroin users displayed increased EPN modulation for heroin cues, whereas this modulation was absent in controls. Conclusions: Drug-related cues acquire motivational salience and automatically capture the attention of heroin users at early processing stages, even when engaged in a non-drug-related task. The EPN to heroin cues could represent a novel electrophysiological index with clinical implications for selecting abstinent drug users who are at increased risk of relapse or to evaluate treatment interventions.

Although food and affective pictures share similar emotional and motivational characteristics, the relationship between the neuronal responses to these stimuli is unclear. Particularly, it is not known whether perceiving and imagining food and affective stimuli elicit similar event-related potential (ERP) patterns. In this study, two ERP correlates, the early posterior negativity (EPN) and the late positive potential (LPP) for perceived and imagined emotional and food photographs were investigated. Thirteen healthy volunteers were exposed to a set of food photos, as well as unpleasant, pleasant, and neutral photos from the International Affective Picture System. In each trial, participants were first asked to view a photo (perception condition), and then to create a visual mental image of it and to rate its vividness (imagery condition). The results showed that during perception, brain regions corresponding to sensorimotor and parietal motivational (defensive and appetitive) systems were activated to different extents, producing a graded pattern of EPN and LPP responses specific to the photo content - more prominent for unpleasant than pleasant and food content. Also, an EPN signature occurred in both conditions for unpleasant content, suggesting that, compared to food or pleasant content, unpleasant content may be attended to more intensely during perception and may be represented more distinctly during imagery. Finally, compared to LLP activation during perception, as well as imagery and perception of all other content, LPP activation was significantly reduced during imagery of unpleasant photos, suggesting inhibition of unwanted memories. Results are framed within a neurocognitive working model of embodied emotions.

ABSTRACTRecently, several event-related potential (ERP) studies investigated the impact of sender attributions on language-based social feedback processing. Results showed very early responses to the social context, while interactions or effects of emotional content started later. However, in these studies, sender attribution was varied across blocks, possibly inducing unspecific, anticipatory effects. Here, who was giving feedback was disclosed simultaneously with the decision itself.Participants’ ERPs differentiated between attributed senders starting with the early posterior negativity. P3 and late positive potential (LPP) amplitudes were also enlarged for the “human sender”. Emotion effects occurred in the P3 and LPP time windows. Further, we found an interaction on the P3: “Human” emotional feedback was selectively amplified. Source analysis localized enhanced processing of “human”-generated feedback in visual areas from around 300 ms after feedback onset and from 400 ms also in temporal regions. Enhancement of “human” emotional feedback resulted from increased activations in the left visual word form area.These findings highlight that decoding who is giving feedback precedes content processing, both in blocked and in randomly alternating situations. Further, in quasi-realistic social contexts, processing of emotional content is selectively amplified. Finally, involvement of semantic language processing structures indicates reintegration of words in a salient context.

The perception of spatial and successive contexts of auditory information develops during human ontogeny. We compared event-related potentials (ERPs) recorded in 5- to 6-year-old children (N = 15) and adults (N = 15) in response to a digital series with omitted digits to explore age differences in the perception of successive auditory information. In addition, ERPs in response to the sound of falling drops delivered binaurally were obtained to examine the spatial context of auditory information. The ERPs obtained from the omitted digits significantly differed in the amplitude and latency of the N200 and P300 components between adults and children, which supports the hypothesis that the perception of a successive auditory structure is less automated in children compared with adults. Although no significant differences were found in adults, the sound of falling drops presented to the left ears of children elicited ERPs with earlier latencies and higher amplitudes of P300 and N400 components in the right temporal area. Stimulation of the right ear caused increasing amplitude of the N100 component in children. Thus, the observed differences in auditory ERPs of children and adults reflect developmental changes in the perception of spatial and successive auditory information.

Social threat detection is important in everyday life. Studies of cortical activity have shown that event-related potentials (ERPs) of motivated attention are modulated during fear conditioning. The time course of motivated attention in learning and extinction of fear is, however, still largely unknown. We aimed to study temporal dynamics of learning processes in classical fear conditioning to social cues (neutral faces) by selecting an experimental setup that produces large effects on well-studied ERP components (early posterior negativity, EPN; late positive potential, LPP; stimulus preceding negativity, SPN) and then exploring small consecutive groups of trials. EPN, LPP, and SPN markedly and quickly increased during the acquisition phase in response to the CS+ but not the CS−. These changes were visible even at high temporal resolution and vanished completely during extinction. Moreover, some evidence was found for component differences in extinction learning, with differences between CS+ and CS− extinguishing faster for late as compared to early ERP components. Results demonstrate that fear learning to social cues is a very fast and highly plastic process and conceptually different ERPs of motivated attention are sensitive to these changes at high temporal resolution, pointing to specific neurocognitive and affective processes of social fear learning.

Event-related potential studies using affective words have indicated that selective attention to valence can increase affective discrimination at early perceptual stages. This effect most likely relies on neural associations between perceptual features of a stimulus and its affective value. Similar to words, emotional expressions in human faces are linked to specific visual elements. Therefore, selectively attending to a given emotion should allow for the preactivation of neural networks coding for the emotion and associated first-order visual elements, leading to enhanced early processing of faces expressing the attended emotion. To investigate this, we employed an expression detection task (N = 65). Fearful, happy, and neutral faces were randomly presented in three blocks while participants were instructed to respond only to one predefined target level of expression in each block. Reaction times were the fastest for happy target faces, which was accompanied by an increased occipital P1 for happy compared with fearful faces. The N170 yielded an arousal effect (emotional > neutral) while both components were not modulated by target status. In contrast, the early posterior negativity (EPN) arousal effect tended to be larger for target compared with nontarget faces. The late positive potential (LPP) revealed large effects of status and expression as well as an interaction driven by an increased LPP specifically for nontarget fearful faces. These findings tentatively indicate that selective attention to facial affect may enhance early emotional processing (EPN) even though further research is needed. Moreover, late controlled processing of facial emotions appears to involve a negativity bias.

ABSTRACTThere is broad evidence that contextual factors influence the processing of emotional facial expressions. Yet temporal-dynamic aspects, inter alia how face processing is influenced by the specific order of neutral and emotional facial expressions, have been largely neglected. To shed light on this topic, we recorded electroencephalogram from 168 healthy participants while they performed a gender-discrimination task with angry and neutral faces. Our event-related potential (ERP) analyses revealed a strong emotional modulation of the N170 component, indicating that the basic visual encoding and emotional analysis of a facial stimulus happen, at least partially, in parallel. While the N170 and the late positive potential (LPP; 400–600 ms) were only modestly affected by the sequence of preceding faces, we observed a strong influence of face sequences on the early posterior negativity (EPN; 200–300 ms). Finally, the differing response patterns of the EPN and LPP indicate that these two ERPs represent distinct processes during face analysis: while the former seems to represent the integration of contextual information in the perception of a current face, the latter appears to represent the net emotional interpretation of a current face.

Investigating the temporal dynamics of natural image processing using event-related potentials (ERPs) has a long tradition in object recognition research. In a classical Go-NoGo task two characteristic effects have been emphasized: an early task independent category effect and a later task-dependent target effect. Here, we set out to use this well-established Go-NoGo paradigm to study the time course of material categorization. Material perception has gained more and more interest over the years as its importance in natural viewing conditions has been ignored for a long time. In addition to analyzing standard ERPs, we conducted a single trial ERP pattern analysis. To validate this procedure, we also measured ERPs in two object categories (people and animals). Our linear classification procedure was able to largely capture the overall pattern of results from the canonical analysis of the ERPs and even extend it. We replicate the known target effect (differential Go-NoGo potential at frontal sites) for the material images. Furthermore, we observe task-independent differential activity between the two material categories as early as 140 ms after stimulus onset. Using our linear classification approach, we show that material categories can be differentiated consistently based on the ERP pattern in single trials around 100 ms after stimulus onset, independent of the target-related status. This strengthens the idea of early differential visual processing of material categories independent of the task, probably due to differences in low-level image properties and suggests pattern classification of ERP topographies as a strong instrument for investigating electrophysiological brain activity.

Cognitive reappraisal of snake and spider pictures: An event-related potentials study