His or mine? The time course of self-other discrimination in emotion processing

This electroencephalography (EEG) study investigated at which temporal processing stages self-other discrimination in emotion processing occurs. EEG was recorded in 23 healthy participants during silent reading of unpleasant, pleasant, and neutral pronoun-noun and article--noun expressions that were related to the participants themselves, related to an unknown third person, or had no self-other reference at all. Self- and other-related pronoun--noun pairs elicited larger cortical negativity relative to the processing of article--noun pairs at left posterior electrodes as early as 200 ms after stimulus onset. In the same time windows (from 200 ms to 300 ms and 300 ms to 400 ms) the emotionality of the words enhanced event-related brain potential (ERP) amplitudes at parieto-occipital electrodes. From 350 ms onwards, processing of self-related unpleasant words elicited larger frontal negativity compared to unpleasant words that were related to the other or that had no reference at all. In addition, processing of pleasant words vs. neutral or unpleasant words elicited larger positive amplitudes over parietal electrodes from 450 ms after stimulus onset, in particular when words were self-related. Our findings demonstrate that for verbal emotional stimuli, self--other discrimination first occurs at higher-order, cortical processing stages. This is consistent with the view that categorization of information according to certain stimulus aspects (self--other reference, emotionality) occurs before its meaning is integrated.     

His or mine? The time course of self–other discrimination in emotion processing

This electroencephalography (EEG) study investigated at which temporal processing stages self–other discrimination in emotion processing occurs. EEG was recorded in 23 healthy participants during silent reading of unpleasant, pleasant, and neutral pronoun–noun and article–noun expressions that were related to the participants themselves, related to an unknown third person, or had no self–other reference at all. Self- and other-related pronoun–noun pairs elicited larger cortical negativity relative to the processing of article–noun pairs at left posterior electrodes as early as 200 ms after stimulus onset. In the same time windows (from 200 ms to 300 ms and 300 ms to 400 ms) the emotionality of the words enhanced event-related brain potential (ERP) amplitudes at parieto-occipital electrodes. From 350 ms onwards, processing of self-related unpleasant words elicited larger frontal negativity compared to unpleasant words that were related to the other or that had no reference at all. In addition, processing of pleasant words vs. neutral or unpleasant words elicited larger positive amplitudes over parietal electrodes from 450 ms after stimulus onset, in particular when words were self-related. Our findings demonstrate that for verbal emotional stimuli, self–other discrimination first occurs at higher-order, cortical processing stages. This is consistent with the view that categorization of information according to certain stimulus aspects (self–other reference, emotionality) occurs before its meaning is integrated.     

How ‘love’ and ‘hate’ differ from ‘sleep’: Using combined electro/magnetoencephalographic data to reveal the sources of early cortical responses to emotional words

Emotional words—as symbols for biologically relevant concepts—are preferentially processed in brain regions including the visual cortex, frontal and parietal regions, and a corticolimbic circuit including the amygdala. Some of the brain structures found in functional magnetic resonance imaging are not readily apparent in electro‐ and magnetoencephalographic (EEG; MEG) measures. By means of a combined EEG/MEG source localization procedure to fully exploit the available information, we sought to reduce these discrepancies and gain a better understanding of spatiotemporal brain dynamics underlying emotional‐word processing. Eighteen participants read high‐arousing positive and negative, and low‐arousing neutral nouns, while EEG and MEG were recorded simultaneously. Combined current‐density reconstructions (L2‐minimum norm least squares) for two early emotion‐sensitive time intervals, the P1 (80–120 ms) and the early posterior negativity (EPN, 200–300 ms), were computed using realistic individual head models with a cortical constraint. The P1 time window uncovered an emotion effect peaking in the left middle temporal gyrus. In the EPN time window, processing of emotional words was associated with enhanced activity encompassing parietal and occipital areas, and posterior limbic structures. We suggest that lexical access, being underway within 100 ms, is speeded and/or favored for emotional words, possibly on the basis of an “emotional tagging” of the word form during acquisition. This gives rise to their differential processing in the EPN time window. The EPN, as an index of natural selective attention, appears to reflect an elaborate interplay of distributed structures, related to cognitive functions, such as memory, attention, and evaluation of emotional stimuli. Hum Brain Mapp 35:875–888, 2014. © 2012 Wiley Periodicals, Inc.     

An attention modulated response to disgust in human ventral anterior insula

The human brain is expert in analyzing rapidly and precisely facial features, especially emotional expressions representing a powerful communication vector. The involvement of insula in disgust recognition has been reported in behavioral and functional imaging studies. However, we do not know whether specific insular fields are involved in disgust processing nor what the processing time course is. Using depth electrodes implanted during presurgical evaluation of patients with drug-refractory temporal lobe epilepsy, we recorded intracerebral event-related potentials to human facial emotional expressions, that is, fear, disgust, happiness, surprise, and neutral expression. We studied evoked responses in 13 patients with insular contacts to specify the insular fields involved in disgust processing and assess the timing of their activation. We showed that specific potentials to disgust beginning 300 milliseconds after stimulus onset and lasting 200 milliseconds were evoked in the ventral anterior insula in four patients. The occurrence and latency of event-related potentials to disgust in the ventral anterior insula were affected by selective attention. The analysis of spatial and temporal characteristics of insular responses to disgust facial expression lead us to underline the crucial role of ventral anterior insula in the categorization of facial emotional expressions, particularly the disgust.     

Selective visual attention to emotional words: Early parallel frontal and visual activations followed by interactive effects in visual cortex

Human brains spontaneously differentiate between various emotional and neutral stimuli, including written words whose emotional quality is symbolic. In the electroencephalogram (EEG), emotional–neutral processing differences are typically reflected in the early posterior negativity (EPN, 200–300 ms) and the late positive potential (LPP, 400–700 ms). These components are also enlarged by task‐driven visual attention, supporting the assumption that emotional content naturally drives attention. Still, the spatio‐temporal dynamics of interactions between emotional stimulus content and task‐driven attention remain to be specified. Here, we examine this issue in visual word processing. Participants attended to negative, neutral, or positive nouns while high‐density EEG was recorded. Emotional content and top‐down attention both amplified the EPN component in parallel. On the LPP, by contrast, emotion and attention interacted: Explicit attention to emotional words led to a substantially larger amplitude increase than did explicit attention to neutral words. Source analysis revealed early parallel effects of emotion and attention in bilateral visual cortex and a later interaction of both in right visual cortex. Distinct effects of attention were found in inferior, middle and superior frontal, paracentral, and parietal areas, as well as in the anterior cingulate cortex (ACC). Results specify separate and shared mechanisms of emotion and attention at distinct processing stages. Hum Brain Mapp 37:3575–3587, 2016. © 2016 Wiley Periodicals, Inc .     

Negative content enhances stimulus‐specific cerebral activity during free viewing of pictures,faces, and words

Negative visual stimuli have been found to elicit stronger brain activation than do neutral stimuli. Such emotion effects have been shown for pictures, faces, and words alike, but the literature suggests stimulus‐specific differences regarding locus and lateralization of the activity. In the current functional magnetic resonance imaging study, we directly compared brain responses to passively viewed negative and neutral pictures of complex scenes, faces, and words (nouns) in 43 healthy participants (21 males) varying in age and demographic background. Both negative pictures and faces activated the extrastriate visual cortices of both hemispheres more strongly than neutral ones, but effects were larger and extended more dorsally for pictures, whereas negative faces additionally activated the superior temporal sulci. Negative words differentially activated typical higher‐level language processing areas such as the left inferior frontal and angular gyrus. There were small emotion effects in the amygdala for faces and words, which were both lateralized to the left hemisphere. Although pictures elicited overall the strongest amygdala activity, amygdala response to negative pictures was not significantly stronger than to neutral ones. Across stimulus types, emotion effects converged in the left anterior insula. No gender effects were apparent, but age had a small, stimulus‐specific impact on emotion processing. Our study specifies similarities and differences in effects of negative emotional content on the processing of different types of stimuli, indicating that brain response to negative stimuli is specifically enhanced in areas involved in processing of the respective stimulus type in general and converges across stimuli in the left anterior insula.     

Brain activation during direct and indirect processing of positive and negative words

The effects of task conditions on brain activation to emotional stimuli are poorly understood. In this event-related fMRI study, brain activation to negative and positive words (matched for arousal) and neutral words was investigated under two task conditions. Subjects either had to attend to the emotional meaning (direct task) or to non-emotional features of the words (indirect task). Regardless of task, positive vs. negative words led to increased activation in the ventral medial prefrontal cortex, while negative vs. positive words induced increased activation of the insula. Compared to neutral words, all emotional words were associated with increased activation of the amygdala. Finally, the direct condition, as compared to the indirect condition, led to enhanced activation to emotional vs. neutral words in the dorsomedial prefrontal cortex and the anterior cingulate cortex. These results suggest valence and arousal dependent brain activation patterns that are partially modulated by participants’ processing mode of the emotional stimuli.     

Saying it with feeling: neural responses to emotional vocalizations.

To determine how vocally expressed emotion is processed in the brain, we measured neural activity in healthy volunteers listening to fearful, sad, happy and neutral non-verbal vocalizations. Enhanced responses to emotional vocalizations were seen in the caudate nucleus, as well as anterior insular, temporal and prefrontal cortices. The right amygdala exhibited decreased responses to fearful vocalizations as well as fear-specific inhibitory interactions with left anterior insula. A region of the pons, implicated in acoustic startle responses also showed fear-specific interactions with the amygdala. The data demonstrate: firstly, that processing of vocal emotion involves a bilaterally distributed network of brain regions; and secondly, that processing of fear-related auditory stimuli involves context-specific interactions between the amygdala and other cortical and brainstem regions implicated in fear processing.     

Modulation of early conflict processing: N200 responses to emotional words in a flanker task

Recent evidence shows that emotion can facilitate the processing of conflict. This effect is subserved by a neural network including the ventral and dorsal portions of the anterior cingulate cortex and the amygdala. However, the time course of emotional modulation of conflict processing is unknown. Therefore, we presented emotional and neutral words in a version of the flanker task and recorded event-related brain potentials (ERP). Reaction times replicated accelerated conflict processing in emotional compared to neutral trials. We also observed a conflict-related negativity at 200 ms after stimulus onset. Interestingly, this N200 amplitude difference was enhanced in emotional trials. These data indicate an early influence of emotion on the processing of conflict. Such an adaptive mechanism ensures rapid resolution of conflict in potentially threatening situations.     

Topography of evoked brain activity during mental arithmetic and language tasks: sex differences

We studied visual information processing using two different tasks in a group of 10 female and 10 male healthy, right-handed adults. Subjects solved arithmetic tasks shown sequentially on a computer monitor, and they also compared words presented as anagrams. The experimental design allowed us to compare the effects of reading or actively processing a given stimulus. Task difficulty was varied in three steps ('easy', 'medium', 'hard') after an independent group of 81 young adults had judged the stimulus material according to difficulty by answering questionnaires. Brain activity was recorded from an array of 30 electrodes extending from the inion to 5% anterior of F2. For each subject mean potentials were averaged off-line after screening the EEG for artifacts. Components were determined quantitatively as epochs of stable topography resulting in 10 independent components occurring within 1200 ms after stimulus onset. Significant effects were seen with field strength and scalp topography: simply reading the stimuli yielded significantly smaller amplitudes than when the subjects actively processed the same stimuli. Females had consistently larger global field power than males, and they also displayed different scalp field topography of various components. In addition, processing anagrams was accompanied by larger field strength than mental arithmetic. The scalp field distributions were also affected by sex, task type and difficulty indicating the activation of different neuronal assemblies during visual information processing of males and females. Many effects were seen at short latencies in the order of 70-120 ms indicating very early selective processing of visual stimuli where specific differences were introduced by sex and task parameters.     

Affective resonance in response to others’ emotional faces varies with affective ratings and psychopathic traits in amygdala and anterior insula

Despite extensive research on the neural basis of empathic responses for pain and disgust, there is limited data about the brain regions that underpin affective response to other people’s emotional facial expressions. Here, we addressed this question using event-related functional magnetic resonance imaging to assess neural responses to emotional faces, combined with online ratings of subjective state. When instructed to rate their own affective response to others’ faces, participants recruited anterior insula, dorsal anterior cingulate, inferior frontal gyrus, and amygdala, regions consistently implicated in studies investigating empathy for disgust and pain, as well as emotional saliency. Importantly, responses in anterior insula and amygdala were modulated by trial-by-trial variations in subjective affective responses to the emotional facial stimuli. Furthermore, overall task-elicited activations in these regions were negatively associated with psychopathic personality traits, which are characterized by low affective empathy. Our findings suggest that anterior insula and amygdala play important roles in the generation of affective internal states in response to others’ emotional cues and that attenuated function in these regions may underlie reduced empathy in individuals with high levels of psychopathic traits.     

Amygdala responsiveness to emotional words is modulated by subclinical anxiety and depression

Several neuroimaging studies underlined the importance of the amygdala and prefrontal brain structures (e.g. dorsolateral prefrontal cortex [DLPFC]) for the processing of emotional stimuli and for emotion regulation. Many studies used visual scenes or faces as emotion-inducing material, and there is evidence that negative or positive words activate emotion-processing brain regions in the same way. However, no study so far focused on the influence of subclinical measures of anxiety or depression on the neural processing of emotional words. In this fMRI-study, we therefore investigated brain activation to emotional words in relation to subclinical measures of trait anxiety and depression in a sample of 21 healthy subjects. We also assessed effects of subclinical anxiety and depression on amygdala-prefrontal coupling during negative (versus neutral) word reading. Both negative and positive words activated the amygdala, and negative-word processing revealed a positive correlation between amygdala activity and scores of trait anxiety and subclinical depression. During negative versus neutral word reading, subjects with high trait anxiety also showed a stronger functional coupling between left amygdala and left DLPFC. These results suggest a modulation of negative-word processing by subclinical depression and anxiety, as well as possible prefrontal compensatory processes during unintentional emotion regulation in subjects with higher trait anxiety.     

Visual processing of facial affect

To evaluate the role of the fusiform gyrus in identifying and processing facial emotional expression in humans, MEG data were collected while six healthy subjects judged whether photographs of faces displayed emotion (happiness or disgust) compared to neutral faces and equiluminant scrambled faces. For all six subjects, a magnetic source localizing to right fusiform gyrus was evident approximately 150 ms following presentation of face stimuli, but not following non-face stimuli. MEG source strength for this component was greatest for happy, intermediate for disgust, and lowest for neutral facial expressions, suggesting that activity in fusiform gyrus is sensitive to both face-specific stimuli and to the affective content of the face. These findings are considered in the context of a specialized neural face-dependent information system.     

Disgust and happiness recognition correlate with anteroventral insula and amygdala volume respectively in preclinical Huntington's disease

Patients with Huntington's disease (HD) can show disproportionate impairments in recognizing facial signals of disgust, but the neural basis of this deficit remains unclear. Functional imaging studies have implicated the anterior insula in the ability to recognize disgust, but have identified other structures as well, including the basal ganglia. In view of variable insula and basal ganglia volume changes in HD, we used voxel-based morphometry to map regional variations in gray matter (GM) volume in participants carrying the mutation for HD, and correlated this with their performance on a test of facial emotion recognition for six basic emotions (disgust, fear, anger, happiness, sadness, surprise). The volume of the anteroventral insula was strongly correlated with performance on the disgust recognition task. The amygdala volume (bilaterally) correlated with the ability to recognize happy facial expressions. There was marked specificity of the regional correlations for the emotion involved. Recognition of other emotion expressions, or more general cognitive or motor performance as measured by a standardized rating scale, did not correlate with regional brain volume in this group. Control participants showed no effect for any measure. The strong linear correlations for disgust and happiness recognition imply direct involvement of the anterior insula in disgust appreciation, and a similar role for the amygdala in recognizing happy facial expressions. The absence of a significant correlation with the basal ganglia suggests a less critical role for these structures in disgust recognition than has previously been suggested. The findings also highlight the role of neurodegenerative diseases combined with statistical imaging techniques in elucidating the brain basis of behavior and cognition.     

Neural correlates of alexithymia: A meta-analysis of emotion processing studies

Alexithymia is a personality trait characterized by difficulties in the experience and cognitive processing of emotions. It is considered a risk factor for a range of psychiatric and neurological disorders. Functional neuroimaging studies investigating the neural correlates of alexithymia have reported inconsistent results. To integrate previous findings, we conducted a parametric coordinate-based meta-analysis including fifteen neuroimaging studies on emotion processing in alexithymia. During the processing of negative emotional stimuli, alexithymia was associated with a diminished response of the amygdala, suggesting decreased attention to such stimuli. Negative stimuli additionally elicited decreased activation in supplementary motor and premotor brain areas and in the dorsomedial prefrontal cortex, possibly underlying poor empathic abilities and difficulties in emotion regulation associated with alexithymia. Positive stimuli elicited decreased activation in the right insula and precuneus, suggesting reduced emotional awareness in alexithymia regarding positive affect. Independent of valence, higher (presumably compensatory) activation was found in the dorsal anterior cingulate possibly indicating increased cognitive demand. These results suggest valence-specific as well as valence-independent effects of alexithymia on the neural processing of emotions.     

Face-selective spectral changes in the human fusiform gyrus.

OBJECTIVE: To characterize ventral occipitotemporal and prefrontal EEG during cognitive processing. METHODS: Depth probes were implanted for seizure localization in 16 pharmaco-resistant epileptics. Probes penetrated from middle temporal through fusiform to lingual gyrus, and from inferior frontal to anterior cingulate gyrus. Event-related potentials (ERPs) and event-related spectral power (ERSP) were calculated during delayed recognition for faces or words. RESULTS: Face stimuli evoked a broadband fusiform ERSP increase from 5 to 45 Hz at 150-210 ms after stimulus onset. This ERSP increase was immediately followed by an ERSP decrease in the same region from 300 to 1000 ms. Both the early increased ERSP and the late decreased ERSP, were greater for faces than words. Simultaneous with the late temporal ERSP decrease, the prefrontal depth EEG displayed a low frequency (5-12 Hz) ERSP increase to face and word stimuli. CONCLUSION: Early temporal ERSP increases occur at a time when the fusiform gyrus is thought to contribute to face processing. This increase is also reflected in spectral analysis of the ERP, but the late temporal ERSP decrease and frontal ERSP increase are not. Thus, intracranial recordings in humans demonstrate event-related fluctuations in EEG spectral power with clear anatomical, temporal and cognitive specificity.     

Spatiotemporal dynamics of affective picture processing revealed by intracranial high‐gamma modulations

Our comprehension of the neural mechanisms underlying emotional information processing has largely benefited from noninvasive electrophysiological and functional neuroimaging techniques in recent years. However, the spatiotemporal dynamics of the neural events occurring during emotional processing remain imprecise due to the limited combination of spatial and temporal resolution provided by these techniques. This study examines the modulations of high‐frequency activity of intracranial electroencephalography recordings associated with affective picture valence, in epileptic patients awaiting neurosurgery. Recordings were obtained from subdural grids and depth electrodes in eight patients while they viewed a series of unpleasant, pleasant and neutral pictures from the International Affective Picture System. Broadband high‐gamma (70–150 Hz) power was computed for separate 100‐ms time windows and compared according to ratings of emotional valence. Compared to emotionally neutral or pleasant pictures, unpleasant stimuli were associated with an early and long‐lasting (≈200–1,000 ms) bilateral increase in high‐gamma activity in visual areas of the occipital and temporal lobes, together with a late and transient (≈500–800 ms) decrease found bilaterally in the lateral prefrontal cortex (PFC). Pleasant pictures were associated with increased gamma activity in the occipital cortex, compared to the emotionally neutral stimuli. Consistent with previous studies, our results provide direct evidence of emotion‐related modulations in the visual ventral pathway during picture processing. Results in the lateral PFC also shed light on the neural mechanisms underlying its role in negative emotions processing. This study demonstrates the utility of intracranial high‐gamma modulations to study emotional process with a high spatiotemporal precision. Hum Brain Mapp, 36:16–28, 2015.. © 2014 Wiley Periodicals, Inc.     

Emotional self-reference: brain structures involved in the processing of words describing one's own emotions

The present functional magnetic resonance imaging study investigated the role of emotion-related (e.g., amygdala) and self-related brain structures (MPFC in particular) in the processing of emotional words varying in stimulus reference. Healthy subjects (N = 22) were presented with emotional (pleasant or unpleasant) or neutral words in three different conditions: (1) self (e.g., my fear), (2) other (e.g., his fear) and (3) no reference (e.g., the fear). Processing of unpleasant words was associated with increased amygdala and also insula activation across all conditions. Pleasant stimuli were specifically associated with increased activation of amygdala and insula when related to the self (vs. other and no reference). Activity in the MPFC (vMPFC in particular) and anterior cingulate cortex (ACC) was preferentially increased during processing of self-related emotional words (vs. other and no reference). These results demonstrate that amygdala activation in response to emotional stimuli is modulated by stimulus reference and that brain structures implicated in emotional and self-related processing might be important for the subjective experience of one's own emotions.     

Preferential responses in amygdala and insula during presentation of facial contempt and disgust

Some authors consider contempt to be a basic emotion while others consider it a variant of disgust. The neural correlates of contempt have not so far been specifically contrasted with disgust. Using functional magnetic resonance imaging (fMRI), we investigated the neural networks involved in the processing of facial contempt and disgust in 24 healthy subjects. Facial recognition of contempt was lower than that of disgust and of neutral faces. The imaging data indicated significant activity in the amygdala and in globus pallidus and putamen during processing of contemptuous faces. Bilateral insula and caudate nuclei and left as well as right inferior frontal gyrus were engaged during processing of disgusted faces. Moreover, direct comparisons of contempt vs. disgust yielded significantly different activations in the amygdala. On the other hand, disgusted faces elicited greater activation than contemptuous faces in the right insula and caudate. Our findings suggest preferential involvement of different neural substrates in the processing of facial emotional expressions of contempt and disgust.     

Neural activity of the anterior insula in emotional processing depends on the individuals' emotional susceptibility

Differences in personality factors between individuals may manifest themselves with different patterns of neural activity while individuals process stimuli with emotional content. We attempted to verify this hypothesis by investigating emotional susceptibility (ES), a specific emotional trait of the human personality defined as the tendency to "experience feelings of discomfort, helplessness, inadequacy and vulnerability" after exposure to stimuli with emotional valence. By administering a questionnaire evaluating the individuals' ES, we selected two groups of participants with high and low ES respectively. Then, we used functional magnetic resonance imaging to investigate differences between the groups in the neural activity involved while they were processing emotional stimuli in an explicit (focusing on the content of the stimuli) or an incidental (focusing on spatial features of the stimuli, irrespectively of their content) way. The results showed a selective difference in brain activity between groups only in the explicit processing of the emotional stimuli: bilateral activity of the anterior insula was present in subjects with high ES but not in subjects with low ES. This difference in neural activity within the anterior insula proved to be purely functional since no brain morphological differences were found between groups, as assessed by a voxel-based morphometry analysis. Although the role of the anterior insula in the processing of contexts perceived as emotionally salient is well established, the present study provides the first evidence of a modulation of the insular activity depending on the individuals' ES trait of personality.