Event-related brain potential correlates of emotional face processing

Results from recent event-related brain potential (ERP) studies investigating brain processes involved in the detection and analysis of emotional facial expression are reviewed. In all experiments, emotional faces were found to trigger an increased ERP positivity relative to neutral faces. The onset of this emotional expression effect was remarkably early, ranging from 120 to 180ms post-stimulus in different experiments where faces were either presented at fixation or laterally, and with or without non-face distractor stimuli. While broadly distributed positive deflections beyond 250ms post-stimulus have been found in previous studies for non-face stimuli, the early frontocentrally distributed phase of this emotional positivity is most likely face-specific. Similar emotional expression effects were found for six basic emotions, suggesting that these effects are not primarily generated within neural structures specialised for the automatic detection of specific emotions. Expression effects were eliminated when attention was directed away from the location of peripherally presented emotional faces, indicating that they are not linked to pre-attentive emotional processing. When foveal faces were unattended, expression effects were attenuated, but not completely eliminated. It is suggested that these ERP correlates of emotional face processing reflect activity within a neocortical system where representations of emotional content are generated in a task-dependent fashion for the adaptive intentional control of behaviour. Given the early onset of the emotion-specific effects reviewed here, it is likely that this system is activated in parallel with the ongoing evaluation of emotional content in the amygdala and related subcortical brain circuits.     

Psychophysiological correlates of face processing in social phobia

Social phobia has been associated with abnormal processing of angry faces, which directly signal disapproval--a situation that social phobics fear. This study investigated the electrophysiological correlates of emotional face processing in socially phobic and non-phobic individuals. Subjects identified either the gender (modified emotional Stroop task) or the expression of angry, happy, or neutral faces. Social phobics showed no deviations from controls in reaction times, heart rates, P1, or P2 amplitudes in response to angry faces, although elevated FSS scores were associated with higher P1 amplitudes in social phobic persons. In addition, social phobic persons showed enhanced right temporo-parietal N170 amplitudes in response to angry faces in the emotion identification task. Furthermore, higher scores on the Social Phobia and Anxiety Inventory (SPAI) were associated as a trend with larger N170 amplitudes in response to angry faces in the emotion identification task. Thus, the present results suggest that social phobics show abnormalities in the early visual processing of angry faces, as reflected by the enhanced right-hemispheric N170 when the emotion of the angry face was the focus of attention, while behavioral responses and heart rates showed no evidence for preferred processing of angry facial expressions.     

Affective processing of loved faces: Contributions from peripheral and central electrophysiology

Research on the neural mechanisms of face identity constitutes a fruitful method to explore the affective contributions to face processing. Here, we investigated central and peripheral electrophysiological indices associated with the perception of loved faces. Subjects viewed black-and-white photographs of faces that belonged to one of five categories: loved ones, famous people, unknown people, babies, and neutral faces from the Eckman and Friesen system. Subcategories of loved faces included romantic partner, parents, siblings, second-degree relatives, and friends. Pictures were presented in two separate blocks, differing in viewing time (0.5 s vs. 4 s), inter-stimulus interval (1.2 s vs. 18 s), and number of face presentations (200 vs. 50). Heart rate, skin conductance, electromyography of the zygomatic muscle, and event-related potentials (ERPs) were obtained while participants passively viewed the pictures. Subjective picture ratings of valence, arousal, and dominance were obtained at the end of the experiment. Both central and peripheral electrophysiological measures differentiated faces of loved ones from all other categories by eliciting higher heart rate, skin conductance, and zygomatic activity, as well as larger amplitudes of the late ERP components P3 and LPP. Loved faces also resulted in higher valence and arousal, but lower dominance ratings. Additional differences were found among subcategories of loved faces. Faces of romantic partners elicited higher physiological (skin conductance and zygomatic activity) and subjective (emotional arousal) responses than parents, siblings, or friends, suggesting that looking at the image of someone we love evokes strong positive affect and emotional/cognitive arousal that go beyond a feeling of familiarity or simple recognition.     

情绪词汇认知加工诱发电位时空模式的脑功能研究

目的应用多通道事件相关电位(event-related potential,ERP)分析技术,探讨正常青年受试者对情绪性词汇认知加工脑神经功能电活动机制。方法应用不同情绪效价的情绪刺激图片对31例健康志愿者进行情绪效价5个水平情绪脑电诱发电位的测试判别,观察受试者对5个情绪效价水平情绪词汇的情绪反应。结果 ERPs统计参数映像图(SPM)结果,对词汇情绪性加工的显著性差异最早可见于刺激后60~200ms;中后期(刺激后420~960ms)极负性和中性情绪反应显著性差异表现为右腹侧记忆-注意整合网络出现刺激负荷效应。极正性和中性情绪反应差异为中期(刺激后320~420ms)的左顶、颞、枕,晚期(刺激后680~1 000ms)见到右额中央负荷效应。极正性和极负性情绪反应差异于刺激后400~1 000ms见于双侧眶额皮层、腹内侧前额皮层、前扣带回皮层和躯体感觉皮层等脑区的广泛记忆-注意整合网络引起更强的激活。结论个体认知行为差异和社会环境背景影响不同情绪效价情绪性词汇的加工,不同情绪效价的情绪性词汇加工过程中存在显著性差异。正负性情绪词汇的加工是双侧半球广泛脑区的记忆-注意整合网络激活效应,并存在脑的偏侧化激活效应。     

Abnormal processing of emotional prosody in Williams syndrome: an event-related potentials study

Williams syndrome (WS), a neurodevelopmental genetic disorder due to a microdeletion in chromosome 7, is described as displaying an intriguing socio-cognitive phenotype. Deficits in prosody production and comprehension have been consistently reported in behavioral studies. It remains, however, to be clarified the neurobiological processes underlying prosody processing in WS.This study aimed at characterizing the electrophysiological response to neutral, happy, and angry prosody in WS, and examining if this response was dependent on the semantic content of the utterance. A group of 12 participants (5 female and 7 male), diagnosed with WS, with age range between 9 and 31 years, was compared with a group of typically developing participants, individually matched for chronological age, gender and laterality. After inspection of EEG artifacts, data from 9 participants with WS and 10 controls were included in ERP analyses.Participants were presented with neutral, positive and negative sentences, in two conditions: (1) with intelligible semantic and syntactic information; (2) with unintelligible semantic and syntactic information (‘pure prosody’ condition). They were asked to decide which emotion was underlying the auditory sentence.Atypical event-related potentials (ERP) components were related with prosodic processing (N100, P200, N300) in WS. In particular, reduced N100 was observed for prosody sentences with semantic content; more positive P200 for sentences with semantic content, in particular for happy and angry intonations; and reduced N300 for both types of sentence conditions.These findings suggest abnormalities in early auditory processing, indicating a bottom-up contribution to the impairment in emotional prosody processing and comprehension. Also, at least for N100 and P200, they suggest the top-down contributions of semantic processes in the sensory processing of speech. This study showed, for the first time, that abnormalities in ERP measures of early auditory processing in WS are also present during the processing of emotional vocal information. This may represent a physiological signature of underlying impaired on-line language and socio-emotional processing.     

An electrocortical investigation of emotional face processing in military-related posttraumatic stress disorder

PTSD is a disorder of emotion dysregulation. Although much work has intended to elucidate the neural underpinnings of the disorder, much remains unknown about the neurobiological substrates of emotion dysregulation in PTSD. In order to assess the relationship between a neural measure of attention to emotion (i.e. the late positive potential; LPP) and PTSD symptoms, EEG was recorded and examined as a potential predictor of military-related PTSD symptoms in a sample of 73 OEF/OIF/OND veterans. Results revealed that higher PTSD symptoms were related to an attenuated LPP response to angry facial expressions. This finding was not observed for happy or fearful faces. The current study provides initial evidence that, in a relatively young, mostly male sample of OEF/OIF/OND veterans, hyporeactivity to angry faces at the neural level may provide phenotypic data to characterize individual differences in PTSD symptom severity. This work may assist in future studies that seek to examine useful psychophysiologic targets for treatment and early interventions.     

Differentiating cortical patterns of cognitive dysfunction in schizophrenia and posttraumatic stress disorder

Comparative studies are needed to determine whether the cognitive impairments found in various psychiatric disorders are specific to those disorders, or are a more universal consequence of mental illness. This study compares the patterns of cognitive dysfunction in two conditions characterized by working memory dysfunction, schizophrenia and posttraumatic stress disorder (PTSD). Three matched groups (Schizophrenia, PTSD, Control) of 16 subjects had event related potentials recorded, using a 27 electrode array, while they performed a working memory auditory target detection task. Both disorders were associated with impaired task performance, with greater impairment in schizophrenia. Reduction in N1 amplitude was found only in schizophrenia, and an increase in target N2 amplitude and latency was found only in PTSD. Both patient groups showed a reduction in the amplitude of the non-target and target P3, but the groups were distinguished by a reduction in non-target parietal P3 amplitude in the schizophrenia group and a reduction in target P3 amplitude over the left posterior parietal region in the PTSD Group. This study demonstrates that there are specific patterns of cognitive dysfunction associated with schizophrenia and with PTSD.     

Rapid extraction of emotional expression: evidence from evoked potential fields during brief presentation of face stimuli

Although the emotional expression of faces is believed to be accessed rapidly, previous ERP studies hardly found correlates of these processes. Here, we report findings from a study that investigated dichoptic binocular interaction using emotional face stimuli. Thirty-one subjects were briefly presented with schematic normal and scrambled faces (of neutral, positive, or negative expression) that occurred simultaneously in the left and right visual fields. Stimuli for both eyes could be congruent (control) or incongruent (dichoptic). Subjects decided which of the superimposed images in both hemi-fields appeared more "face-like" and during this task, the EEG was recorded from 30 channels. VEPs were analysed topographically according to the influence of the different experimental conditions (defined by presentation form, emotional expression, and location). Behavioural responses to the ambiguous dichoptic stimuli demonstrated a functional eye dominance not related to visual acuity and conventional eye preference. Electrophysiological data revealed three components with mean latencies of 85, 160, and 310 ms. Topography of the second component (equivalent to the face-related N170) differed in left-right and anterior-posterior direction compared with simple checkerboard stimuli. Dichoptic presentation caused reduced field strength of all three, and increased latency of the first component. Faces with negative expression yielded largest field strength of the second and third components. Besides that, emotional expression affected topography not only of late, but also the first component. This provides new evidence about the timing of perceptual processes related to facial expression, indicating that already VEP components occurring at 80-90 ms are sensitive to emotional content.     

Memory retrieval processing: neural indices of processes supporting episodic retrieval

Event-related potentials (ERPs) were acquired during separate test phases of a verbal recognition memory exclusion task in order to contribute to current understanding of the functional significance of differences between ERPs elicited by new (unstudied) test words, which are assumed to index processes engaged in pursuit of task-relevant information. Participants were asked to endorse old words from one study task (targets), and to reject new test words as well as those from a second study task (non-targets). The study task designated as the target category varied across test phases. The left-parietal ERP old/new effect - the electrophysiological signature of recollection - was reliable for targets and for non-targets in all test phases, consistent with the view that participants recollected information about both of these classes of test word. The contrast between the ERPs evoked by new test words separated according to target designation revealed no reliable differences. These findings contrast with those in a recent study in which the same tasks were used, but in which the accuracy of task judgments was markedly higher (Dzulkifli, M.A., & Wilding, E. L. (2005). Electrophysiological indices of strategic episodic retrieval processing. Neuropsychologia, 43, 1152-1162). In that study, there were reliable differences between the ERPs evoked by the two classes of new words, but reliable left-parietal ERP old/new effects for targets only. In combination, the findings suggest that differences between ERPs evoked by new test words can reflect processes that are important for controlling what kinds of information will and will not be recollected.     

Neural correlates of performance monitoring in adult patients with attention deficit hyperactivity disorder (ADHD)

Introduction. In this study, the neural correlates of error processing in adult patients with attention deficit hyperactivity disorder (ADHD) are to be investigated for the first time. Recent studies in children with ADHD suggested, with some inconsistencies, deficits in error processing. Based on an analogue study with students, we hypothesized that ADHD patients show reduced amplitudes in the event-related potential (ERP) of the Pe (error positivity) but normal amplitudes of the ERN (error-related negativity) after incorrect responses. Method. In this study we investigated 34 adult ADHD patients and 34 healthy controls with a modified version of the Eriksen flanker task while recording the neural activity with 26 scalp EEG electrodes. Patients discontinued all medication at least 3 days prior to investigation. Age was included as a control variable for the statistical analyses. Results and conclusion. As hypothesized, we found reduced Pe amplitudes, but also reduced ERN values, in ADHD patients. Importantly, theses differences as well as the deficits in behavioural performance were mainly detectable in the younger subsample, but not in the elderly subsample. Our results indicate that adult ADHD patients are characterized by deficits in error processing, which vanish with age.     

The role of trauma-related distractors on neural systems for working memory and emotion processing in posttraumatic stress disorder

The relevance of emotional stimuli to threat and survival confers a privileged role in their processing. In PTSD, the ability of trauma-related information to divert attention is especially pronounced. Information unrelated to the trauma may also be highly distracting when it shares perceptual features with trauma material. Our goal was to study how trauma-related environmental cues modulate working memory networks in PTSD. We examined neural activity in participants performing a visual working memory task while distracted by task-irrelevant trauma and non-trauma material. Recent post-9/11 veterans were divided into a PTSD group (n = 22) and a trauma-exposed control group (n = 20) based on the Davidson trauma scale. Using fMRI, we measured hemodynamic change in response to emotional (trauma-related) and neutral distraction presented during the active maintenance period of a delayed-response working memory task. The goal was to examine differences in functional networks associated with working memory (dorsolateral prefrontal cortex and lateral parietal cortex) and emotion processing (amygdala, ventrolateral prefrontal cortex, and fusiform gyrus). The PTSD group showed markedly different neural activity compared to the trauma-exposed control group in response to task-irrelevant visual distractors. Enhanced activity in ventral emotion processing regions was associated with trauma distractors in the PTSD group, whereas activity in brain regions associated with working memory and attention regions was disrupted by distractor stimuli independent of trauma content. Neural evidence for the impact of distraction on working memory is consistent with PTSD symptoms of hypervigilance and general distractibility during goal-directed cognitive processing.     

军人创伤后应激障碍患者的关联性负变异常变化及临床随访

目的　了解军人创伤后应激障碍 (PTSD)患者关联性负变 (CNV)的特征和治疗缓解后CNV的变化。方法　应用美国NicoletBravo型脑诱发电位仪及光、声两种成对刺激方法 ,对 6 6例发病期PTSD患者 (患者组 )和 5 6名健康军人 (对照组 )进行CNV测定以及症状自评量表 (SCL - 90 )和事件影响量表 (IES)评定 ,并对患者组中的 6 0例进行了临床随访。结果　患者组发病期M1潜伏期延迟 (P <0 0 1) ,M2 波幅增高 (P <0 0 1) ,命令信号后负变化(PINV)出现率增高 (P <0 0 1) ;SCL - 90及IES总分及其部分因子分升高 (P <0 0 1) ;CNV变异指标与SCL - 90及IES总分及其部分因子分显著相关 (P <0 0 1或 0 0 5 )。患者组康复期M1潜伏期、M2 波幅和PINV出现率 ,以及SCL- 90与IES总分及其部分因子分均恢复至正常值内 (与发病期比较P <0 0 1,与对照组比较P >0 0 5 ) ,且治疗前后CNV变异指标差值与精神症状减分率显著相关 (P <0 0 1或 0 0 5 )。结论　PTSD患者的CNV变化可能是状态标志。     

Error and post-error processing in children with attention-deficit/hyperactivity disorder: An electrical neuroimaging study

ObjectiveInaccurate and inconsistent response styles in attention-deficit/hyperactivity disorder (ADHD) have been observed in a wide variety of cognitive tasks, in line with regulatory deficit models of ADHD. Event-related potential (ERP) studies of error processing have provided evidence for these models, but are limited in specificity. We aimed to improve the isolation, localization and identification of error (self-monitoring and adaptive control) and post-error (implementation of cognitive control) processing in ADHD.MethodsERPs were obtained for 46 ADHD and 51 typically developing (TD) children using the stop-signal task. Response-locked error (Ne and Pe) and stimulus-locked post-error (N2) components were compared between groups. Ne/Pe were corrected for preceding stimulus overlap and group differences were localized.ResultsNe was intact, while Pe amplitude was markedly reduced in children with ADHD (ηp² = 0.14). Pe differences were localized in the dorsal posterior/midcingulate (BA31/24) cortex. While the TD group showed increased N2 amplitude in post-error trials (ηp² = 0.24), localized in the left ventrolateral prefrontal cortex (VLPFC) and angular gyrus, the ADHD group did not.ConclusionsSelf-regulation deficits in ADHD are associated with later stages of error processing and subsequent implementation of cognitive control.SignificanceWe contribute to the literature by further specifying error processing deficits in ADHD.     

Electrophysiological correlates of familiarity in recognition memory and exclusion tasks

ERPs were acquired in the test phases of three memory experiments, where three classes of word were presented. These were: (i) words encountered in a prior study phase (studied words), (ii) words presented at test for the first time (new words), and (iii) new words repeated after a lag of 7-9 intervening words (repeated test words). In experiments 1 and 2, participants were asked to respond on one key to studied words and on another to new as well as to repeated test words. In experiment 3, a binary response was again required, but in this case repeated test and studied words were assigned to the same key. In each experiment, the principal focus for analysis was on the differences between the ERPs at mid-frontal electrode locations from 300 to 500 ms post-stimulus that were associated with incorrect responses to studied words (misses) and correct responses to new words. It has been proposed that relatively greater positivity for studied than for new words at this locus reflects the greater familiarity of studied than of unstudied words. ERPs elicited by misses were reliably more positive-going than those elicited by correct rejections in experiments 1 and 2 only. These findings support the link between this modulation of the electrical record and familiarity in so far as the designs of the experiments lead to the prediction that the average level of familiarity associated with misses should be higher in the first two experiments than in the third. In combination with findings in other studies, these data support dual-process accounts of recognition memory.     

Brain functional effects of electroconvulsive therapy during emotional processing in major depressive disorder

BackgroundIn treatment-resistant major depressive disorder (MDD), electroconvulsive therapy (ECT) is a treatment with high efficacy. While knowledge regarding changes in brain structure following ECT is growing, the effects of ECT on brain function during emotional processing are largely unknown.ObjectiveWe investigated the effects of ECT on the activity of the anterior cingulate cortex (ACC) and amygdala during negative emotional stimuli processing and its association with clinical response.MethodsIn this non-randomized longitudinal study, patients with MDD (n = 37) were assessed before and after treatment with ECT. Healthy controls (n = 37) were matched regarding age and gender. Functional magnetic resonance imaging (fMRI) was obtained twice, at baseline and after six weeks using a supraliminal face-matching paradigm. In order to evaluate effects of clinical response, additional post-hoc analyses were performed comparing responders to non-responders.ResultsAfter ECT, patients with MDD showed a statistically significant increase in ACC activity during processing of negative emotional stimuli (p_FWE = .039). This effect was driven by responders (p_FWE = .023), while non-responders showed no increase. Responders also had lower pre-treatment ACC activity compared to non-responders (p_FWE = .025). No significant effects in the amygdala could be observed.ConclusionsECT leads to brain functional changes in the ACC, a relevant region for emotional regulation during processing of negative stimuli. Furthermore, baseline ACC activity might serve as a biomarker for treatment response. Findings are in accordance with recent studies highlighting properties of pre-treatment ACC to be associated with general antidepressive treatment response.     

Social and emotional processing in Prader-Willi syndrome: genetic subtype differences

Background

People with Prader-Willi syndrome (PWS) demonstrate social dysfunction and increased risk of autism spectrum disorder, especially those with the maternal uniparental disomy (mUPD) versus paternal deletion genetic subtype. This study compared the neural processing of social (faces) and nonsocial stimuli, varying in emotional valence, across genetic subtypes in 24 adolescents and adults with PWS.

Methods

Upright and inverted faces, and nonsocial objects with positive and negative emotional valence were presented to participants with PWS in an oddball paradigm with smiling faces serving as targets. Behavioral and event-related potential (ERP) data were recorded.

Results

There were no genetic subtype group differences in accuracy, and all participants performed above chance level. ERP responses revealed genetic subtype differences in face versus object processing. In those with deletions, the face-specific posterior N170 response varied in size for face stimuli versus inverted faces versus nonsocial objects. Persons with mUPD generated N170 of smaller amplitude and showed no stimulus differentiation. Brain responses to emotional content did not vary by subtype. All participants elicited larger posterior and anterior late positive potential responses to positive objects than to negative objects. Emotion-related differences in response to faces were limited to inverted faces only in the form of larger anterior late positive potential amplitudes to negative emotions over the right hemisphere. Detection of the target smiling faces was evident in the increased amplitude of the frontal and central P3 responses but only for inverted smiling faces.

Conclusion

Persons with the mUPD subtype of PWS may show atypical face versus object processes, yet both subtypes demonstrated potentially altered processing, attention to and/or recognition of faces and their expressions.