Hemispheric asymmetries in the perception of emotional and neutral faces

The Role of Temperament and Gender in Functional Hemispheric Asymmetry and the Perception of Emotion

Research investigating the relation between Functional Hemispheric Asymmetry (FHA) and the perception of affect in clinical as well as normal populations, is characterized by contradictory findings regarding the role of the different hemispheres, especially as regards the perception of various valencies of emotions. Although various methodological problems or error variances are often blamed for the contradictory findings and general lack of consensus, the literature is increasingly pointing to the existence of evidently reliable individual differences between people regarding their hemispheric functioning. The problem investigated in this study was to determine the possible role of some organismic variables in FHA. The objectives of this study were to determine whether there were significant differences in the direction of FHA-differences, as well as the relative performance, of groups divided according to gender and temperament characteristics, and whether the relevant organismic variables offered a possible means of explaining the contradictions in research results on FHA and the perception of emotion. The subject population ( N = 112) comprised four groups of right-handed students selected in terms of gender and temperament (introversion-extraversion). Differential hemispheric performance in terms of response accuracy and latency was determined by means of the Divided Visual Field Technique (DVFT). The results indicated that gender but not the temperament dimension of introversion-extraversion, plays a significant role in the degree and direction of FHA in the perception of emotion. It appears that the organismic variable gender could possibly offer a partial explanation for the contradictory results in the literature specifically with regard to FHA in the perception of emotion generally, and in respect of different valencies of emotion. However, the lack of significance in some of the results, especially with regard to men, impedes a firm empirical conclusion and explanation of the results.

Early neural activation during facial affect processing in adolescents with Autism Spectrum Disorder

Impaired social interaction is one of the hallmarks of Autism Spectrum Disorder (ASD). Emotional faces are arguably the most critical visual social stimuli and the ability to perceive, recognize, and interpret emotions is central to social interaction and communication, and subsequently healthy social development. However, our understanding of the neural and cognitive mechanisms underlying emotional face processing in adolescents with ASD is limited. We recruited 48 adolescents, 24 with high functioning ASD and 24 typically developing controls. Participants completed an implicit emotional face processing task in the MEG. We examined spatiotemporal differences in neural activation between the groups during implicit angry and happy face processing. While there were no differences in response latencies between groups across emotions, adolescents with ASD had lower accuracy on the implicit emotional face processing task when the trials included angry faces. MEG data showed atypical neural activity in adolescents with ASD during angry and happy face processing, which included atypical activity in the insula, anterior and posterior cingulate and temporal and orbitofrontal regions. Our findings demonstrate differences in neural activity during happy and angry face processing between adolescents with and without ASD. These differences in activation in social cognitive regions may index the difficulties in face processing and in comprehension of social reward and punishment in the ASD group. Thus, our results suggest that atypical neural activation contributes to impaired affect processing, and thus social cognition, in adolescents with ASD.

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The ability to recognize and interpret emotions is central to social interaction.

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Deficits in social interactions are hallmarks of autism spectrum disorder (ASD).

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Adolescents with and without ASD completed an emotional face task in MEG.

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MEG data showed atypical neural activity in ASD to both angry and happy faces.

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Insula, cingulate, temporal and orbitofrontal activities were particularly affected in the ASD group.

Lateralized hybrid faces: evidence of a valence-specific bias in the processing of implicit emotions

It is well known that hemispheric asymmetries exist for both the analyses of low-level visual information (such as spatial frequency) and high-level visual information (such as emotional expressions). In this study, we assessed which of the above factors underlies perceptual laterality effects with "hybrid faces": a type of stimulus that allows testing for unaware processing of emotional expressions, when the emotion is displayed in the low-frequency information while an image of the same face with a neutral expression is superimposed to it. Despite hybrid faces being perceived as neutral, the emotional information modulates observers' social judgements. In the present study, participants were asked to assess friendliness of hybrid faces displayed tachistoscopically, either centrally or laterally to fixation. We found a clear influence of the hidden emotions also with lateral presentations. Happy faces were rated as more friendly and angry faces as less friendly with respect to neutral faces. In general, hybrid faces were evaluated as less friendly when they were presented in the left visual field/right hemisphere than in the right visual field/left hemisphere. The results extend the validity of the valence hypothesis in the specific domain of unaware (subcortical) emotion processing.

Recognition of Natural Expressions of Emotion by CVA Patients with Damage to the Left or Right Hemisphere

The present study investigated the ability of cerebrovascular accident (CVA) patients to perceive emotions portrayed by realistic stimuli. Statistical analyses demonstrated that CVA patients with damage to either the right or left cerebral hemisphere performed, on average, as well as controls did in perceiving emotions. However, a case study of one patient suggested that there may be a subset of CVA patients with right parieto-occipital damage who have deficits in the perception of negative emotions. The performance of this participant also indicated that deficits in emotion perception are ameliorated to some extent when patients are provided with realistic, complex stimuli that include a range of auditory and visual cues.

The right-hemisphere and valence hypotheses: could they both be right (and sometimes left)?

The two halves of the brain are believed to play different roles in emotional processing, but the specific contribution of each hemisphere continues to be debated. The right-hemisphere hypothesis suggests that the right cerebrum is dominant for processing all emotions regardless of affective valence, whereas the valence specific hypothesis posits that the left hemisphere is specialized for processing positive affect while the right hemisphere is specialized for negative affect. Here, healthy participants viewed two split visual-field facial affect perception tasks during functional magnetic resonance imaging, one presenting chimeric happy faces (i.e. half happy/half neutral) and the other presenting identical sad chimera (i.e. half sad/half neutral), each masked immediately by a neutral face. Results suggest that the posterior right hemisphere is generically activated during non-conscious emotional face perception regardless of affective valence, although greater activation is produced by negative facial cues. The posterior left hemisphere was generally less activated by emotional faces, but also appeared to recruit bilateral anterior brain regions in a valence-specific manner. Findings suggest simultaneous operation of aspects of both hypotheses, suggesting that these two rival theories may not actually be in opposition, but may instead reflect different facets of a complex distributed emotion processing system.

Left hemisphere specialization for response to positive emotional expressions: A divided output methodology

An extensive literature credits the right hemisphere with dominance for processing emotion. Conflicting literature finds left hemisphere dominance for positive emotions. This conflict may be resolved by attending to processing stage. A divided output (bimanual) reaction time paradigm in which response hand was varied for emotion (angry; happy) in Experiments 1 and 2 and for gender (male; female) in Experiment 3 focused on response to emotion rather than perception. In Experiments 1 and 2, reaction time was shorter when right-hand responses indicated a happy face and left-hand responses an angry face, as compared to reversed assignment. This dissociation did not obtain with incidental emotion (Experiment 3). Results support the view that response preparation to positive emotional stimuli is left lateralized.

Hemispheric asymmetry in the processing of emotional content in word meanings: the effect of current and past depression

We examined hemispheric lateralization of emotion processing by comparing the performance of clinically depressed, previously depressed, and control individuals on a divided visual field task. Participants were asked to make affective valence judgments for each in a series of laterally presented person-descriptive adjectives. Study results suggest that the right cerebral hemisphere (RH) is preferentially sensitive to the affective context of language. Among targets presented to the RH, depressed and previously depressed participants were significantly faster and more accurate in their judgments of negative target words, while controls responded more quickly and accurately to positive target words. No such effects were observed for targets presented to the left hemisphere. It is hypothesized that affective sensitivity may result in differences in semantic network organization across individuals who vary in affective experience.

Facial affect recognition in criminal psychopaths

Prior studies provide consistent evidence of deficits for psychopaths in processing verbal emotional material but are inconsistent regarding nonverbal emotional material. To examine whether psychopaths exhibit general versus specific deficits in nonverbal emotional processing, 34 psychopaths and 33 nonpsychopaths identified with Hare's (R. D. Hare, 1991) Psychopathy Checklist--Revised were asked to complete a facial affect recognition test. Slides of prototypic facial expressions were presented. Three hypotheses regarding hemispheric lateralization anomalies in psychopaths were also tested (right-hemisphere dysfunction, reduced lateralization, and reversed lateralization). Psychopaths were less accurate than nonpsychopaths at classifying facial affect under conditions promoting reliance on right-hemisphere resources and displayed a specific deficit in classifying disgust. These findings demonstrate that psychopaths exhibit specific deficits in nonverbal emotional processing.

Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children

Thirty-five prepubertal children, 17 boys and 18 girls, between the ages of 8 and 11 years, were studied to examine electrophysiological and cognitive sex differences during a face-recognition-memory (FRM) task and a facial-affect-identification task (FAIT). All participants were prepubertal, as determined by J. M. Tanner's (1962) staging and endocrine evaluation. Sex-dependent event-related potential (ERP) amplitude asymmetries were found during FRM. Boys displayed greater right versus left ERP amplitude to auditory tone probes during the task, whereas girls displayed the opposite pattern. In addition, positive correlations were obtained between ERP amplitude during FRM and FAIT accuracy scores for boys, but not for girls. Results suggest that girls and boys may use different neuronal systems in the processing of faces and facial affect. Findings are consistent with developmental theories regarding sex differences in visuospatial processing.

Emotional and physiological responses to false feedback

The relationship between autonomic-visceral arousal and emotional experience is unclear. The attribution or cognitive-arousal theory of emotional experience posits that emotional experience is dependent on both visceral-autonomic nervous system feedback and the cognitive interpretation of the stimulus that induced this visceral activation. The finding that false cardiac feedback can alter emotional experience suggests that it may be the conscious perception that one is aroused, together with the cognitive interpretation of the stimulus that are important in developing emotional experience. Because the right hemisphere appears to play a special role in modulating arousal and interpreting emotional stimuli, it is possible that right hemisphere damage may interfere with developing the computations needed for emotional experience. To test this hypothesis we exposed men, both neurologically intact and those with right and left hemisphere lesions, to emotionally provocative pictures that were paired with false cardiac feedback, and examined the effects of this false feedback on their ratings of attractiveness of these pictures and their cardiac reactivity to this information. Subjects with left hemisphere damage, but not right hemisphere damage, showed significant changes in their emotional rating whereas control subjects showed marginal reactivity in their emotional ratings. Subjects with left hemisphere damage also showed significant changes in their cardiac reactivity. This finding is consistent with prior reports that indicate, when compared to right hemisphere damaged patients and normal controls, patients with left hemisphere lesions have an increased visceral-autonomic response to stimuli. These findings further provide support for the postulate that it is the cognitive interpretation of perceived physiological arousal together with the cognitive interpretation of the stimulus that is important in the development of emotional judgment and experience. These results do not support the approach-left hemisphere/avoidance-right hemisphere dichotomy, but instead suggest that left hemisphere damage increases reactivity to false feedback, and that the intact right hemisphere function integrates the cognitive interpretation of the emotional information and perceived arousal that lead to that emotional judgment. That these subjects showed no consistent relationship between their measures of cardiac reactivity and their ratings of attractiveness detracts from the James-Lange and attribution theories. These subjects also showed no consistent relationship between their knowledge of affective physiological reactivity and their ratings of attractiveness, or between their knowledge of physiological reactivity and actual measures of cardiac reactivity, suggesting that other neuropsychological factors are involved in making an emotional judgment.

Impairments in judgment of chimeric faces by schizophrenic and affective patients

The hypothesis that schizophrenic and affective patients have differential impairments in judgment of facial emotional expressions was tested on 55 right-handed patients: 15 in each of two groups of schizophrenic patients, with positive and negative symptoms; and 10 in each of two groups of bipolar affective patients, in manic and depressive states. In addition, 37 normal control subjects were also tested. The subjects were presented with eight schematic drawings of chimeric faces (each depicting a positive emotion in a given hemiface, and a negative emotion in the other hemiface), as well as with two drawings of composite faces (each depicting either a positive or a negative emotion). Subjects judged the emotions depicted by the facial expressions, as well as their intensity. The data, analyzed by analyses of variance, showed that normals judged the chimeric expressions on the basis of the emotions depicted by the left hemifaces. This tendency was weaker among the psychiatric patients. Schizophrenics with negative symptoms judged positive expressions in the left hemifaces as depicting negative emotions, and negative expressions as depicting positive emotions. Schizophrenics with positive symptoms and manic patients judged all expressions as depicting positive emotions. Depressive patients showed a stronger tendency to judge negative expressions as depicting negative emotions than positive expressions as depicting positive emotions. No significant group differences appeared in judgment of composite faces (except for schizophrenic with negative symptoms who were more accurate in judging positive than negative expressions). Patients performances were interpreted in terms of differential dysfunctions in posterior areas of the right cerebral hemisphere which might be associated with bilateral effects of dysfunctions in anterior cerebral areas.

Faces and emotions: brain electric field sources during covert emotional processing

Covert brain activity related to task-free, spontaneous (i.e. unrequested), emotional evaluation of human face images was analysed in 27-channel averaged event-related potential (ERP) map series recorded from 18 healthy subjects while observing random sequences of face images without further instructions. After recording, subjects self-rated each face image on a scale from "liked" to "disliked". These ratings were used to dichotomize the face images into the affective evaluation categories of "liked" and "disliked" for each subject and the subjects into the affective attitudes of "philanthropists" and "misanthropists" (depending on their mean rating across images). Event-related map series were averaged for "liked" and "disliked" face images and for "philanthropists" and "misanthropists". The spatial configuration (landscape) of the electric field maps was assessed numerically by the electric gravity center, a conservative estimate of the mean location of all intracerebral, active, electric sources. Differences in electric gravity center location indicate activity of different neuronal populations. The electric gravity center locations of all event-related maps were averaged over the entire stimulus-on time (450 ms). The mean electric gravity center for disliked faces was located (significant across subjects) more to the right and somewhat more posterior than for liked faces. Similar differences were found between the mean electric gravity centers of misanthropists (more right and posterior) and philanthropists. Our neurophysiological findings are in line with neuropsychological findings, revealing visual emotional processing to depend on affective evaluation category and affective attitude, and extending the conclusions to a paradigm without directed task.

The role of the right hemisphere in the physiological and cognitive components of emotional processing

Right hemisphere specialization for emotional processing was investigated using behavioral and psychophysiological methods. Fifty undergraduates were shown slides depicting negative emotional and neutral scenes briefly lateralized to the right or left cerebral hemispheres and asked to categorize each as emotional or neutral. Pulse volume and heart rate (HR) measured physiological processing and reaction time measured cognitive processing. The largest vasoconstriction responses and HR deceleration were obtained for emotional items in the right hemisphere. However, reaction time failed to show right hemisphere superiority in perceptual/cognitive processing, demonstrating instead slowest responses to emotional stimuli presented to the right hemisphere together with evidence for left hemisphere competence. Selective right hemispheric activation in autonomic responses, combined with the lack of right hemisphere specialization in the cognitive task, suggests that the physiological response system rather than the perceptual/cognitive system is the locus of the right hemisphere superiority for emotion.

Hemispheric asymmetry as a function of handedness: perception of facial affect stimuli

Hemispheric asymmetry in 14 left- and 14 right-handed persons shown tachistoscopically presented emotional stimuli to left and right visual fields was examined using a forced-choice, reaction-time paradigm in which subjects were asked to identify positive and negative faces. Neutral faces were included within the two-alternative forced-choice paradigm. Reaction time and response-bias measures were recorded. Analysis indicated differential lateralization for left-handed and right-handed subjects with respect to neutral affective stimuli. While right-handed subjects' perceptions of neutral stimuli remained consistent across visual fields, left-handed ones identified neutral stimuli as more positive (happy) when presented to the left visual field and negative (angry) when presented to the right visual field. Implications for differential lateralization patterns among left- and right-handed adults are discussed.

An integrative psychophysiological approach to brain hemisphere functions in schizophrenia

The present paper proposes a new psychophysiological approach to the genesis of positive and negative schizophrenic symptoms. According to this approach, the initial factor in schizophrenic disorders is a functional insufficiency of the right hemisphere which can be determined by early emotional experience in combination with subtle brain damage. This functional insufficiency causes (a) the inability to grasp and select information before its realization; and (b) the inability to produce a polysemantic context which is crucial for creativity, psychological defense, and the restoration of search activity, all of which determine psychophysiological adaptation to the environment. Right hemisphere insufficiency causes left hemisphere hyperactivity as an ineffective attempt to compensate for this functional deficiency. As a result, normal search activity is replaced by artificial search activity which is represented by "positive" symptoms, and which uses the predisposition of the left hemisphere's catecholamine system for its increased activity. The suggestion is made that cognitive impairment in schizophrenia (the inability to use appropriate previous information in relation to current perceptual input) is related to the competition between information processing which requires left hemisphere activity, and the formation of positive symptoms, also based on left hemisphere activity.

Patterns of perceptual asymmetry in processing facial expression

The paper reports four visual half-field experiments on the recognition of schematic faces whose emotional expression varied. Experiments I and II tested accuracy of recognition in a match-to-sample task. The results confirmed an overall left visual-field superiority in face recognition, but an analysis of a subset of the stimuli indicated that the direction and magnitude of the perceptual asymmetry depend upon the sign of the emotional expression. A replot of the results based on direct scaling of emotional expression (Experiment III) revealed an asymmetry gradient shifting from a left visual-field superiority for faces displaying hostile, aggressive emotions. When the stimuli are rotated 180 degrees the faces lose their emotional expression and no visual half-field asymmetry in recognition was observed in this condition (Experiment IV). It is concluded that emotional signals are processed independently of pattern, object and face recognition, and that the relative contribution of the left and right cerebral hemispheres to processing of emotional signals varies according to the type of emotion displayed.

Neural and behavioral correlates of emotion recognition in children and adults

Event-related potentials (ERPs), accuracy scores, and reaction times were used to examine the recognition of emotional expressions. Adults and 7-year-old children saw upright and inverted chromatic slides of the facial expressions of happiness, fear, surprise, and anger, and were asked to press a button for either "happy" or "angry" faces. A positive-going waveform (P300) was apparent at parietal scalp (Pz) and at left and right temporal scalp. Although the behavioral data were similar for both children and adults (e.g., both had more difficulty recognizing angry expressions than happy ones, and angry expressions were more difficult to recognize upside-down than were happy faces), the ERPs indicated that children responded differently than adults did to happy and angry expressions. Adults showed greater P300 amplitude to happy faces, while children showed greater P300 amplitude to angry faces. In addition, for adults, but not children, there were greater P300 amplitude responses at right vs. left temporal scalp.

Differential asymmetries for positive and negative emotion: hemisphere or stimulus effects?

Two experiments were carried out to determine whether expressive asymmetries in facial stimuli might underlie evidence of differential hemispheric responses to positive and negative emotion. Experiment 1 systematically varied stimulus orientation; Experiment 2 included both normally oriented and reversed (mirror-image) faces. We replicated previous reports of a left field advantage for happy faces and a right field superiority for sad faces only when normally oriented faces were used. Mirror-image stimuli tended to produce the opposite pattern of results, and a combination of the two (Exp. 2) eliminated the visual field differences for each emotion. The findings underscore the importance of controlling for stimulus asymmetries in visual laterality studies, and are discussed in terms of current notions about the lateralization of both the perception and expression of emotion.

Functional Hemispheric Asymmetry and Psychological Differentiation

A differentiation model is proposed in which a relationship between neuropsychological (perceptual) differentiation on the one hand, and psychological (personality) differentiation on the other hand is hypothesized. An empirical investigation of the basic hypothesis is reported. The fit of the global model to empirical data is evaluated with the aid of the RAMONA program for path analysis with latent variables. In the advanced model differentiation is assumed to be a formal property of an organismic system. Neuropsychological differentiation is conceptualized in terms of the extent of functional hemispheric asymmetry (FHA), and operationalized in the auditory and visual modalities with the aid of the dichotic stimulation technique (DST) and the divided visual field technique (DVFT). Psychological differentiation is conceptualized in terms of the degree of healthy, optimal personality functioning (OPF), and is operationalized with indices of communicative competency, degree of self-actualization and of personal autonomy. A significant relationship between FHA and OPF was found. This indicates a correspondence between the degree of differentiation in diverse domains of functioning (perceptual and personality-wise), in healthy, normal subjects. In this study phenomena described in different specialization areas of psychology (neuropsychology and personology) are linked in a shall bridge theory for which empirical support has been found. This is a modest step towards interdisciplinary understanding.