Emotional primes modulate the responses to others’ pain: an ERP study

Previous event-related potential (ERP) and brain imaging studies have suggested observer responses to others’ pain are modulated by various bottom-up and top-down factors, including emotional primes. However, the temporal dynamics underlying the impact of emotional primes on responses to others’ pain remains poorly understood. In the present study, we explored effects of negative, neutral, and positive emotional priming stimuli on behavioral and cortical responses to visual depictions of others in pain. ERPs were recorded from 20 healthy adults, who were presented with painful and non-painful target pictures following observation of negative, neutral, and positive emotional priming pictures. ERP analyses revealed that relative to non-painful pictures, differential P3 amplitudes for painful pictures were larger followed by negative primes than either neutral or positive primes. There were no significant differential P3 amplitudes for painful pictures relative to non-painful pictures were found followed neutral and positive emotional primes. These results suggest that negative emotional primes strengthen observers’ attention toward others’ pain. These results support the threat value of pain hypothesis.     

Event-related beta oscillations are affected by emotional eliciting stimuli

According to previous results, negative emotional facial expressions elicit oscillatory beta responses. The present study analyzes event-related beta oscillations upon presentation of International Affective Picture System (IAPS) and aims to show whether behavior of beta in response to negative IAPS pictures also have similar dynamics. IAPS pictures (unpleasant, pleasant, and neutral) were presented as a block and random passive viewing to 14 healthy subjects (8 male). Only with pictures with similar luminance level were selected as stimuli. Event-Related Potentials (ERPs) were recorded from 30 different scalp locations, and adaptive digital filtering was used for analysis in different frequency windows. The maximum peak-to-peak amplitudes were measured for each subject's averaged beta responses (15–30 Hz) in the 0 and 300 ms time window. Beta responses were significantly higher for unpleasant pictures than for pleasant and neutral pictures (average 50%). Beta responses were significantly higher for unpleasant than for pleasant pictures over frontal, central and parietal electrode sides (p < 0.05). Furthermore, beta responses were significantly higher for unpleasant than for neutral pictures over parietal and occipital electrodes (p < 0.04). In addition, the pleasant pictures elicited higher beta responses than neutral pictures over occipital electrode sites (p < 0.04). The results of the present study indicate that negative emotions are related to increased beta responses in humans, independent of stimulus types (facial expression or IAPS pictures). Accordingly, beta responses to negative emotions are possibly a common phenomenon. The standardization of luminance in pictures may reduce divergences between results from different laboratories.     

Affective modulation of brain potentials to painful and nonpainful stimuli

In accordance with the emotional priming hypothesis, emotions seem to modulate pain perception and pain tolerance thresholds. To further evaluate this association, event-related brain potentials (ERPs) elicited by painful and nonpainful electrical stimuli during processing of positive, neutral, and negative valenced pictures were recorded from 30 healthy volunteers. Valence of pictures affected pain ratings and the N150 elicited by painful stimuli, with lowest amplitudes for positive pictures and highest amplitudes for negative pictures. The P260 elicited by painful and nonpainful stimuli was modulated by arousal with reduced amplitudes with arousing (positive or negative) compared to neutral pictures. N150 amplitudes varying with picture valence seem to reflect an affective modulation of pain perception whereas P260 amplitudes varying with picture arousal rather reflect non-pain-specific attentional processes.     

Negative expectations influence behavioral and ERP responses in the subsequent recognition of expectancy-incongruent neutral events

Previous studies have shown that expectancy incongruence in emotional stimuli influences the encoding (i.e., the first stage of memory processing) of the stimuli. However, it is unknown about whether expectancy incongruence influences later stages of memory processing, such as recognition. To this end, expectancy cues were presented prior to emotional pictures. Most often, the cues accurately indicated the emotional consequences of the pictures, but in some cases the consequence was incongruent with the expectations, and a picture from another emotional category was presented. Afterward, participants completed an unexpected recognition task in which old and novel pictures were not preceded by expectancy cues. The results showed that, in the encoding phase, expectancy incongruence reduced response accuracy when categorizing pictorial emotions, and the effect was smaller for neutral pictures than for negative pictures. ERP results showed stronger and weaker responses to expectancy incongruent pictures compared to congruent pictures in time ranges related to the encoding-related early and middle late positive potential (LPP), respectively. In the subsequent recognition phase, d′ scores were higher for incongruent neutral pictures than for congruent ones. Expectancy incongruence enlarged the P2 response but reduced the recognition-related early LPP response for neutral pictures. However, effects of expectancy incongruence were not seen for negative pictures. Therefore, the findings in the present study indicate that negative expectations influence the later recognition of expectancy incongruent neutral events, whereas negative events are more resistant to the effects of expectation incongruence.     

Appraisal frames of pleasant and unpleasant pictures alter emotional responses as reflected in self-report and facial electromyographic activity

Emotional pictures elicit responses across experiential, behavioral and physiological systems. The magnitude of these responses can be modulated by altering one's interpretation of emotional stimuli. Previous studies have indicated that appraisal frames affect subsequent interpretations of upcoming stimuli so as to alter self-reported emotions, ERP activity and autonomic responses. No studies to date have examined the effect of appraisal frames on expressive behaviors as measured by facial EMG. This study aims to test the hypothesis that appraisal frames can alter both emotional experience and facial expression and attempts to examine their effect on the temporal unfolding of facial expressions. Participants (N=20) were exposed to 125 pairs of appraisal frames (neutral or negative/positive) followed by neutral, unpleasant, or pleasant pictures reflecting five conditions: unpleasant-negative, unpleasant-neutral, pleasant-positive, pleasant-neutral and neutral-neutral. Results indicate that the unpleasant-negative compared to the unpleasant-neutral condition led to greater self-reported unpleasantness and arousal, as well as greater corrugator activity, and the pleasant-positive compared to the pleasant-neutral condition led to greater self-reported pleasantness and zygomaticus activity; modulation of facial responses became evident 0.5-1.0s after stimulus onset. These results suggest that appraisal frames effectively alter both emotional experience and facial expressions.     

Event-related brain potentials and affective responses to threat in spider/snake-phobic and non-phobic subjects.

We investigated cortical responses and valence/arousal ratings of spider phobic, snake phobic, and healthy subjects while they were processing feared, fear-relevant, emotional neutral, and pleasant stimuli. Results revealed significantly larger amplitudes of late ERP components (P3 and late positive complex, LPC) but not of early components (N1, P2, N2) in phobics when subjects were processing feared stimuli. This fear-associated increase of amplitudes of late ERP components in phobic subjects was maximal at centro-parietal and occipital brain sites. Furthermore, phobics but not controls rated feared stimuli to be more negative and arousing than fear-relevant, emotional neutral, and pleasant stimuli. Since late ERP components and valence/arousal ratings were only significantly increased when phobic subjects but not when healthy controls were processing feared stimuli, the present data suggest that P3 and LPC amplitudes represent useful neural correlates of the emotional significance and meaning of stimuli.     

Subnormal short-latency facial mimicry responses to dynamic emotional facial expressions in male adolescents with disruptive behavior disorders and callous-unemotional traits

Using still pictures of emotional facial expressions as experimental stimuli, reduced amygdala responses or impaired recognition of basic emotions were repeatedly found in people with psychopathic traits. The amygdala also plays an important role in short-latency facial mimicry responses. Since dynamic emotional facial expressions may have higher ecological validity than still pictures, we compared short-latency facial mimicry responses to dynamic and static emotional expressions between adolescents with psychopathic traits and normal controls. Facial EMG responses to videos or still pictures of emotional expressions (happiness, anger, sadness, fear) were measured. Responses to 500-ms dynamic expressions in videos, as well as the subsequent 1500-ms phase of maximal (i.e., static) expression, were compared between male adolescents with disruptive behavior disorders and high (n = 14) or low (n = 17) callous-unemotional (CU) traits, and normal control subjects (n = 32). Responses to still pictures were also compared between groups. EMG responses to dynamic expressions were generally significantly smaller in the high-CU group than in the other two groups, which generally did not differ. These group differences gradually emerged during the 500-ms stimulus presentation period but in general they were already seen a few hundred milliseconds after stimulus onset. Group differences were absent during the 1500-ms phase of maximal expression and during exposure to still pictures. Subnormal short-latency mimicry responses to dynamic emotional facial expressions in the high-CU group might have negative consequences for understanding emotional facial expressions of others during daily life when human facial interactions are primarily dynamic.     

Elevated response of human amygdala to neutral stimuli in mild post traumatic stress disorder: neural correlates of generalized emotional response

Previous evidence from functional magnetic resonance imaging (fMRI) studies has shown that amygdala responses to emotionally neutral pictures are exaggerated at a group level in patients with severe post-traumatic stress disorder (PTSD) [Hendler T, Rotshtein P, Yeshurun Y, Weizmann T, Kahn I, Ben-Bashat D, Malach R, Bleich A (2003) Neuroimage 19(3):587–600]. The present fMRI study tested the hypothesis that amygdala responses are elevated not only in response to negative pictures but also to neutral pictures as a function of disease severity in patients with mild symptoms and in subjects who did not develop symptoms. To this end, fMRI scans were performed in 10 patients with mild PTSD and 10 healthy controls (both victims of a bank robbery), during the execution of a visuo-attentional task in which they were asked to observe emotionally negative or neutral pictures. Control subjects showed enhanced amygdala responses to emotionally negative stimuli compared to neutral stimuli. On the contrary, PTSD patients were characterized by high amygdala responses to both neutral and emotional pictures, with no statistically significant difference between the two classes of stimuli. In the entire group, we found correlations among the severity of the PTSD symptoms, task performance, and amygdala activation during the processing of neutral stimuli. Results of this study suggest that amygdala responses and the selectivity of the emotional response to neutral stimuli are elevated as a function of disease severity in PTSD patients with mild symptoms.     

The cognitive consequences of emotion regulation: an ERP investigation

Increasing evidence suggests that emotion regulation (ER) strategies modulate encoding of information presented during regulation; however, no studies have assessed the impact of cognitive reappraisal ER strategies on the processing of stimuli presented after the ER period. Participants in the present study regulated emotions to unpleasant pictures and then judged whether a word was negative or neutral. Electromyographic measures (corrugator supercilli) confirmed that individuals increased and decreased negative affect according to ER condition. Event-related potential analyses revealed smallest N400 amplitudes to negative and neutral words presented after decreasing unpleasant emotions and smallest P300 amplitudes to words presented after increasing unpleasant emotions whereas reaction time data failed to show ER modulations. Results are discussed in the context of the developing ER literature, as well as theories of emotional incongruity (N400) and resource allocation (P300).     

Psychophysiology of spider phobia in 8- to 12-year-old girls

The present investigation focused on late event-related potentials (ERPs) and facial electromyographic (EMG) activity in response to symptom provocation in 8- to 12-year-old spider phobic girls and compared results to those in non-fearful controls. Fourteen patients and 14 controls were presented with phobia-relevant, generally fear-inducing, disgust-inducing and affectively neutral pictures in an EEG/EMG session. ERPs were extracted in the time-windows 340-500 ms (P300) and 550-770 ms (late positive potential, LPP). Relative to controls, phobics showed enhanced amplitudes of P300 and LPP in response to spider pictures. This result is interpreted to reflect motivated attention to emotionally salient stimuli. Moreover, phobics showed enhanced average facial EMG activity of the levator labii and the corrugator supercilii in response to spider pictures, reflecting the negative valence and disgust relevance of spiders. Additionally, spider phobic girls relative to controls showed higher overall disgust proneness and heightened average facial EMG activity in both muscle regions in response to disgust stimuli, possibly revealing a disgust-based origin of spider phobia in children. These aspects should be considered in psychotherapeutic treatment of childhood spider phobia.     

Incidental emotions influence risk preference and outcome evaluation

Incidental emotions, which are irrelevant to the current decision, play a significant role in the decision‐making process. In this study, to investigate the influence of incidental emotions on behavioral, psychological, and electrophysiological responses in the process of decision making, participants were required to perform a monetary gambling task. During the selection stage, an emotional picture, which was chosen from the Chinese Affective Picture System and fell into one of three categories: negative, neutral, and positive, was presented between two alternatives (small/large amount of bet). The pictures were provided to induce incidental emotions. ERPs and self‐rating emotional experiences to outcome feedback were recorded during the task. Behavioral results showed that positive incidental emotions elicited risk preference, but emotional experiences to outcome feedback were not influenced by incidental emotions. The feedback‐related negativity amplitudes were larger in the positive emotion condition than in the negative and neutral emotion conditions for small outcomes (including wins and losses), whereas there was no difference between the three conditions for large outcomes. In addition, the amplitudes of P3 were reduced overall in the negative emotion condition. We suggest that incidental emotions have modulated both the option assessment stage (manifested in behavioral choices) and the outcome evaluation stage (manifested in ERP amplitudes) of decision making unconsciously (indicated by unchanged subjective emotional experiences). The current findings have expanded our understanding of the role of incidental emotion in decision making.     

Do emojis influence social interactions? Neural and behavioral responses to affective emojis in bargaining situations

Emojis are nowadays a common substitute for real facial expressions to integrate emotions in social interaction. In certain contexts, emojis possibly could also transport information beyond emotions, reflecting interindividual differences or social aspects. In this study, we investigated the influence of emojis as socioemotional feedback stimuli on behavior and neural responses in a social decision game. We modified the Ultimatum Game by including emotional feedback provided by the proposer as response to the decision of the participant as receiver. Therefore, we generated identities that differed in their feedback behavior to identify differences in the processing of emotional feedback in a positive (acceptance) versus negative (rejection) frame. Regarding offer sizes, we replicated the valence effect of feedback‐related negativity for small offer sizes evoking more negative brain potentials compared to larger ones. Further, we found an effect of affective emojis on distinct ERPs: A face‐detecting neural component (N170) was examined to be a part of the processing of emojis, which resulted in significantly more negative amplitudes in response to a sad‐looking emoji compared to smiling and neutral ones. Furthermore, P3 amplitudes indicate transmission effects from the feedback emoticons to the neural processing of different offer sizes. In contrast to previous findings, P3 responses of our subjects did not depend on the offer size, but rather by which kind of partner they were made. Since some evaluative processes did not reveal any effects, emojis seem to be less effective than real facial expressions, which convey more information that is socially meaningful.     

Respiratory sinus arrhythmia responses to induced emotional states: effects of RSA indices, emotion induction method, age, and sex

The literature shows large inconsistencies in respiratory sinus arrhythmia (RSA) responses to induced emotional states. This may be caused by differences in emotion induction methods, RSA quantification, and non-emotional demands of the situation. In 83 healthy subjects, we studied RSA responses to pictures and film fragments eliciting six different discrete emotions relative to neutral baseline stimuli. RSA responses were quantified in the time and frequency domain and were additionally corrected for differences in mean heart rate and respiration rate, resulting in eight different RSA response measures. Subjective ratings of emotional stimuli and facial electromyographic responses indicated that pictures and film fragments elicited the intended emotions. Although RSA measures showed various emotional effects, responses were quite heterogeneous and frequently nonsignificant. They were substantially influenced by methodological factors, in particular time vs. frequency domain response measures, correction for changes in respiration rate, use of pictures vs. film fragments, and sex of participants.     

The effect of cognitive reappraisal on physiological reactivity and emotional memory

We investigated the effect of cognitive reappraisal on emotional arousal, facial expressivity and subsequent memory. Men and women viewed emotionally negative pictures while they attempted to either increase or decrease negative emotions elicited by the pictures, or to simply view the pictures. Neutral pictures were also presented with instructions to simply view the pictures. Concurrent changes in emotional arousal and valence were assessed with skin conductance responses (SCRs) and facial corrugator electromyographic responses (EMG), respectively. Picture memory was assessed with an immediate recall test and a delayed recognition test. Relative to simply viewing pictures, voluntary reappraisal to increase negative emotion generated greater facial corrugator EMG and SCR responses, and reappraisal to decrease negative emotion generated decreased corrugator EMG responses. Men showed enhanced recognition for pictures presented during the increase and decrease conditions, whereas women showed comparable recognition performance across all regulation conditions. The modulation of subsequent recognition memory associated with decreasing emotion was inversely associated with changes in physiological responses. Our results suggest that sex is an important factor to consider in determining how reappraisal-induced physiological changes are associated with subsequent changes in memory. These findings contribute to our understanding of how reappraising emotion exerts both immediate and enduring influences on physiological responses and subsequent memory.     

Influence of trait-anxiety on inhibition function: Evidence from ERPs study

Patients suffering from anxiety disorder may experience a few problems in the inhibition function. Using event-related potentials, the current study investigated the differences between subjects with high versus low trait-anxiety when they tried to inhibit disturbances in novel emotional pictures in an oddball task. The results showed that P3 amplitudes evoked by negative pictures relative to neutral pictures were decreased in subjects with high as well as low anxiety. In the high-anxious group, P3 amplitudes were also decreased in the positive condition relative to the neutral condition, whereas in the low anxious group, P3 amplitudes showed no significant differences between the positive and neutral stimuli. This implies that people with high anxiety may exhibit some degree of over-inhibition in emotional processing as compared to people with low anxiety. These people tend to indiscriminately inhibit all types of disturbing emotional information.     

Common and specific brain responses to scenic emotional stimuli

Processing of emotions has been an enduring topic of interest in neuroimaging research, but studies have mostly used facial emotional stimuli. The aim of this study was to determine neural networks involved in emotion processing using scenic emotional visual stimuli. One hundred and twenty photographs from the International Affective Picture System (IAPS), including ecological scenes of disgust, fear, happiness, and sadness, were presented to 40 healthy participants while they underwent functional magnetic imaging resonance (fMRI). Afterwards they evaluated the emotional content of the pictures in an offline task. The occipito-temporal cortex and the amygdala–hippocampal complex showed a non-specific emotion-related activation, which was more marked in response to negative emotions than to happiness. The temporo-parietal cortex and the ventral anterior cingulate gyrus showed deactivation, with the former being marked for all emotions except fear and the latter being most marked for disgust. The fusiform gyrus showed activation in response to disgust and deactivation in response to happiness or sadness. Brain regions involved in processing of scenic emotion therefore resemble those reported for facial expressions of emotion in that they respond to a range of different emotions, although there appears to be specificity in the intensity and direction of the response.     

Event-related potentials (ERPs) to hemifield presentations of emotional stimuli: differences between depressed patients and healthy adults in P3 amplitude and asymmetry.

Depression may involve dysfunction of right parietotemporal cortex, a region activated during perception of affective stimuli. To further test this hypothesis, event-related brain potentials (ERPs) were measured in a paradigm previously shown to produce ERP asymmetries to affective stimuli over parietal sites in healthy adults. Pictures of patients with dermatological diseases showing disordered or healed facial areas before (negative) or after (neutral) surgical treatment were briefly exposed for 250 ms to either the left or right hemifield. ERPs of 30 unmedicated, unipolar depressed patients and 16 healthy adults, all right-handed, were recorded from 30 electrodes. A principal components analysis extracted factors which closely corresponded to distinctive ERP components previously reported for this task (N1, N2, early P3, late P3, slow wave). Significant effects of emotional content, i.e. enhanced amplitudes to negative than neutral stimuli, were found for early and late P3. Control subjects showed significant hemispheric asymmetries of emotional processing for late P3 (peak latency 460 ms), with the largest emotional content effects over the right parietal region. In striking contrast to control subjects, depressed patients did not show an increase in late P3 for negative compared to neutral stimuli over either hemisphere and had smaller late P3 amplitude than control subjects. Patients did, however, show larger early P3 (peak latency 330 ms) to negative than neutral stimuli. Results suggest intact early discrimination but abnormal late appraisal of affective content in depression, which may arise from selective inhibition of right parietal regions integral for perceiving and evaluating emotional stimuli.     

Alexithymic features and automatic amygdala reactivity to facial emotion

Alexithymic individuals have difficulties in identifying and verbalizing their emotions. The amygdala is known to play a central role in processing emotion stimuli and in generating emotional experience. In the present study automatic amygdala reactivity to facial emotion was investigated as a function of alexithymia (as assessed by the 20-Item Toronto Alexithymia Scale). The Beck-Depression Inventory (BDI) and the State-Trait-Anxiety Inventory (STAI) were administered to measure participants' depressivity and trait anxiety. During 3T fMRI scanning, pictures of faces bearing sad, happy, and neutral expressions masked by neutral faces were presented to 21 healthy volunteers. The amygdala was selected as the region of interest (ROI) and voxel values of the ROI were extracted, summarized by mean and tested among the different conditions. A detection task was applied to assess participants' awareness of the masked emotional faces shown in the fMRI experiment. Masked sad and happy facial emotions led to greater right amygdala activation than masked neutral faces. The alexithymia feature difficulties identifying feelings was negatively correlated with the neural response of the right amygdala to masked sad faces, even when controlling for depressivity and anxiety. Reduced automatic amygdala responsivity may contribute to problems in identifying one's emotions in everyday life. Low spontaneous reactivity of the amygdala to sad faces could implicate less engagement in the encoding of negative emotional stimuli.     

Electrophysiological evidence of early processing deficits in alexithymia

Alexithymia describes difficulties to identify and describe one's emotions. Previous research focused on difficulties associated with the later processing stages of appraisal in alexithymia. We tested whether early processing deficits are apparent in alexithymic persons and whether these abnormalities contribute to later processing difficulties. 20 participants were selected and identified as either having high (HDA) or low (LDA) degrees of alexithymia. IAPS pictures were presented while EEG was recorded. For HDA subjects processing of emotional pictures was accompanied by reduced P1 amplitudes most pronounced for pleasant and neutral pictures. In response to unpleasant pictures the P3 amplitudes were reduced. These amplitude modulations were predicted only by one alexithymia facet. P1 amplitudes systematically covaried with P3 amplitudes supporting the assumption that deficits in early emotional processing contribute to later processing deficits.     

Greater impairment in negative emotion evaluation ability in patients with paranoid schizophrenia

To explore whether or not patients with schizophrenia display a more profound impairment of negative emotion processing, we assessed the implicit evaluation of positive and negative emotional stimuli. Twenty patients with schizophrenia (9 paranoid, 11 non-paranoid) and 22 normal controls were instructed to classify emotional pictures according to the intrinsic valence if the pictures were black and white. If the stimuli were color-filtered, participants were instructed to press the positive/negative response key according to the extrinsic valence (assigned valence of color). The error rates of the color-filtered stimuli were used as dependent measures. Normal controls made more errors on trials of the positive pictures when the correct response was the negative response key than when the correct response was the positive response key. The reverse was true on trials of the negative pictures. Patients with schizophrenia, especially paranoid schizophrenia, committed more errors in trials of the positive pictures when the correct response key was the negative response key. However, the reverse was not true on trials of the negative pictures. These findings suggest that patients with paranoid schizophrenia might suffer from an impaired ability to evaluate negative emotions and have a loosening of association within their negative emotional networks.