Emotional and non-emotional facial behaviour in patients with unilateral brain damage

Psychiatric sequelae of stroke affecting the non-dominant cerebral hemisphere

There are a plethora of cognitive sequelae in addition to neglect and extinction that arise with unilateral right hemispheric stroke (RHS). Cognitive deficits following non-dominant (right) hemisphere stroke are common with unilateral neglect and extinction being the most recognized examples. The severity of RHS is usually underestimated by the National Institutes of Health Stroke Scale (NIHSS), which in terms of lateralized right hemisphere cognitive deficits, tests only for visual inattention/extinction. They account for 2 out of 42 total possible points. Additional neuropsychiatric sequelae include but are not limited to deficiencies in affective prosody comprehension and production (aprosodias), understanding and expressing facial emotions, empathy, recognition of familiar faces, anxiety, mania, apathy, and psychosis. These sequelae have a profound impact on patients' quality of life; affecting communication, interpersonal relationships, and the ability to fulfill social roles. They also pose additional challenges to recovery. There is presently a gap in the literature regarding a cohesive overview of the significant cognitive sequelae following RHS. This paper serves as a narrative survey of the current understanding of the subject, with particular emphasis on neuropsychiatric poststroke syndromes not predominantly associated with left hemisphere lesions (LHL), bilateral lesions, hemiplegia, or paralysis. A more comprehensive understanding of the neuropsychological consequences of RHS extending beyond the typical associations of unilateral neglect and extinction may have important implications for clinical practice, including the ways in which clinicians approach diagnostics, treatment, and rehabilitation.

Unilateral Blinking: Insights from Stereo-EEG and Tractography

To study the neuroanatomical correlate of involuntary unilateral blinking in humans, using the example of patients with focal epilepsy. Patients with drug resistant focal epilepsy undergoing presurgical evaluation with stereotactically implanted EEG-electrodes (sEEG) were recruited from the local epilepsy monitoring unit. Only patients showing ictal unilateral blinking or unilateral blinking elicited by direct electrical stimulation were included (n = 16). MRI and CT data were used for visualization of the electrode positions. In two patients, probabilistic tractography with seeding from the respective electrodes was additionally performed. Three main findings were made: (1) involuntary unilateral blinking was associated with activation of the anterior temporal region, (2) tractography showed widespread projections to the ipsilateral frontal, pericentral, occipital, limbic and cerebellar regions and (3) blinking was observed predominantly in female patients with temporal lobe epilepsies. Unilateral blinking was found to be associated with an ipsilateral activation of the anterior temporal region. We suggest that the identified network is not part of the primary blinking control but might have modulating influence on ipsilateral blinking by integrating contextual information.

Disorders of facial emotional expression and comprehension

One of the most important means of communicating emotions is by facial expressions. About 30-40 years ago, several studies examined patients with right and left hemisphere strokes for deficits in expressing and comprehending emotional facial expressions. The participants with right- or left-hemispheric strokes attempted to determine if two different actors were displaying the same or different emotions, to name the different emotions being displayed, and to select the face displaying an emotion named by the examiner. Investigators found that the right hemisphere-damaged group was impaired on all these emotional facial tests and that this deficit was not solely related to visuoperceptual processing defects. Further studies revealed that the patients who were impaired at recognizing emotional facial expressions and who had lost these visual representations of emotional faces often had damage to their right parietal lobe and their right somatosensory cortex. Injury to the cerebellum has been reported to impair emotional facial recognition, as have dementing diseases such as Alzheimer's disease and frontotemporal dementia, movement disorders such as Parkinson's disease and Huntington's disease, traumatic brain injuries, and temporal lobe epilepsy. Patients with right hemisphere injury are also more impaired than left-hemisphere-damaged patients when attempting to voluntarily produce facial emotional expressions and in their spontaneous expression of emotions in response to stimuli. This impairment does not appear to be induced by emotional conceptual deficits or an inability to experience emotions. Many of the disorders that cause impairments of comprehension of affective facial expressions also impair facial emotional expression. Treating the underlying disease may help patients with impairments of facial emotion recognition and expression, but unfortunately, there have not been many studies of rehabilitation.

Neurophysiology of spontaneous facial expressions: II. Motor control of the right and left face is partially independent in adults

Facial expressions are described traditionally as monolithic or unitary entities. However, humans have the capacity to produce facial blends of emotion in which the upper and lower face simultaneously display different expressions. Recent neuroanatomical studies in monkeys have demonstrated that there are separate cortical motor areas for controlling the upper and lower face in each hemisphere that, presumably, also occur in humans. Using high-speed videography, we began measuring the movement dynamics of spontaneous facial expressions, including facial blends, to develop a more complete understanding of the neurophysiology underlying facial expressions. In our part 1 publication in Cortex (2016), we found that hemispheric motor control of the upper and lower face is overwhelmingly independent; 242 (99%) of the expressions were classified as demonstrating independent hemispheric motor control whereas only 3 (1%) were classified as demonstrating dependent hemispheric motor control. In this companion paper (part 2), 251 unitary facial expressions that occurred on either the upper or lower face were analyzed. 164 (65%) expressions demonstrated dependent hemispheric motor control whereas 87 (35%) expressions demonstrated independent or dual hemispheric motor control, indicating that some expressions represent facial blends of emotion that occur across the vertical facial axis. These findings also support the concepts that 1) spontaneous facial expressions are organized predominantly across the horizontal facial axis and secondarily across the vertical facial axis and 2) facial expressions are complex, multi-component, motoric events. Based on the Emotion-type hypothesis of cerebral lateralization, we propose that facial expressions modulated by a primary-emotional response to an environmental event are initiated by the right hemisphere on the left side of the face whereas facial expressions modulated by a social-emotional response to an environmental event are initiated by the left hemisphere on the right side of the face.

Affective communication deficits associated with cerebellar degeneration

The cerebellum has extensive connections with the frontal lobes. Cerebellar injury has been reported to induce frontal-executive cognitive dysfunction and blunting of affect. We examined a patient with idiopathic cerebellar degeneration with impaired family relationships attributed to an "emotional disconnection." Examination revealed ataxia, dysmetria, and adiadochokinesia more severe on the left and frontal-executive dysfunction; memory and cognitive functions were otherwise normal. Testing of emotional communication included assessments of emotional semantic knowledge, emotional prosody, and emotional facial expressions. Comprehension was normal but expression was severely impaired. Cerebellar dysfunction can cause a defect in facial and prosodic emotional communication.

Cerebral localization of functions and the neurology of language: fact versus fiction or is it something else?

Over the last 15 years there has been a burgeoning number of publications using functional brain imaging (>40,000 articles based on an ISI/Web of Science search) to localize behavioral and cognitive processes to specific areas in the human brain that are often not confirmed by traditional, lesion-based studies. Thus, there is a need to reassess what cerebral localization of functions is and is not. Otherwise, there is no rational way to interpret the escalating claims of localization in the functional imaging literature that is taking on the appearance of neurophysiologic "phrenology". This article will present arguments to suggest that functional localization in the brain is a robust but very dynamic, four-dimensional process. It is a learned phenomenon driven over time by large-scale, spatially distributed, neural networks seeking to efficiently maximize the processing, storage, and manipulation of information for cognitive and behavioral operations. Because of historical considerations and space limitations, the main focus will be on localization of language-related functions whose theoretical neurological basis can be generalized for any complex cognitive-behavioral function.

Disturbances in affective communication following brain injury

PRIMARY OBJECTIVE

Disturbances in affect expression and perception are often clinically observed in brain injured patients during the acute stages of recovery. This study examined whether such disturbances are related to the acute nature of the injury or specific type of injury in patients with stroke (CVA) versus traumatic brain injury (TBI).

RESEARCH DESIGN

Retrospective cohort of patients seen for inpatient rehabilitation following brain injury.

PROCEDURES

Participants were 27 CVA and 27 TBI patients. Their performance was compared to 27 normal controls on the BNI Screen for Higher Cerebral Functions.

OUTCOMES AND RESULTS

While both patient groups performed significantly worse than the control group on affect expression, perception and spontaneity (p<0.01), the CVA group performed significantly worse than the TBI group (p<0.01) on affect perception. Results of this study document disturbances in affect in brain injured patients and highlight the importance of assessing affect during early recovery.

Human Facial Expressions Are Organized Functionally Across the Upper-Lower Facial Axis

Most clinical research has focused on intensity differences of facial expressions between the right and left hemiface to explore lateralization of emotions in the brain. Observations by social psychologists, however, suggest that control of facial expression is organized predominantly across the upper-lower facial axis because of the phenomena of facial blends: simultaneous display of different emotions on the upper and lower face. Facial blends are related to social emotions and development of display rules that allow individuals to sculpt facial expressions for social and manipulative purposes. We have demonstrated that facial blends of emotion are more easily and accurately posed on the upper-lower than right-left hemiface, and that upper facial emotions are processed preferentially by the right hemisphere whereas lower facial emotions are processed preferentially by the left hemisphere. Based on these results, recent anatomical studies showing separate cortical areas for motor control of upper and lower face and the neurology of posed and spontaneous expressions of emotion, a functional-anatomic model of how the forebrain modulates facial expressions, is presented. The unique human ability to produce facial blends of emotion is, most likely, an adaptive modification linked to the evolution of speech and language. NEUROSCIENTIST 13(5):433—446, 2007.

Dysfunctional facial emotional expression and comprehension in a patient with corticobasal degeneration

Patients with corticobasal degeneration (CBD) frequently develop orofacial apraxia but little is known about CBD's influence on emotional facial processing. We describe a patient who developed a facial apraxia including an impaired ability to voluntarily generate facial expressions with relative sparing of spontaneous emotional faces. Her ability to interpret the facial expressions of others was also severely impaired. Despite these deficits, the patient had normal affect and normal speech, including expressive and receptive emotional prosody. As patients with corticobasal degeneration are known to manifest both orofacial apraxia and visuospatial dysfunction this patient's expressive and receptive deficits may be independent manifestations of the same underlying disease process. Alternatively, these functions may share a common neuroanatomic substrate that degenerates with CBD.

Facial paresis in patients with mesial temporal sclerosis: clinical and quantitative MRI-based evidence of widespread disease

PURPOSE

To assess the frequency and significance of facial paresis (FP) in a well-defined cohort of mesial temporal lobe epilepsy (MTLE) patients.

METHODS

One hundred consecutive patients with MRI findings consistent with mesial temporal sclerosis (MTS) and concordant electroclinical data underwent facial motor examination at rest, with voluntary expression, and with spontaneous smiling. Hippocampal, amygdaloid, and temporopolar (TP) volumetric measures were acquired. Thirty healthy subjects, matched according to age and sex, were taken as controls.

RESULTS

Central-type FP was found in 46 patients. In 41 (89%) of 46, it was visualized at rest, with voluntary and emotional expression characterizing true facial motor paresis. In 33 (72%) of 46 patients, FP was contralateral to the side of MTS. By using a 2-SD cutoff from the mean of normal controls, we found reduction in TP volume ipsilateral to MTS in 61% of patients with FP and in 33% of those without (p = 0.01). Febrile seizures as initial precipitating injury (IPI) were observed in 34% of the patients and were classified as complex in 12 (26%) of 46 of those with FP and in five (9%) of 54 of those without (p = 0.02). The presence of FP was significantly associated with a shorter latent period and younger age at onset of habitual seizures, in particular, with secondarily generalized tonic-clonic seizures.

CONCLUSIONS

Facial paresis is a reliable lateralizing sign in MTLE and was associated with history of complex febrile seizures as IPI, younger age at onset of disease, and atrophy of temporal pole ipsilateral to MTS, indicating more widespread disease.

Social functioning and facial emotional expression in neurological and psychiatric disorders

This study examined the relationship between facial expression and social functioning in schizophrenic, depressed, right-brain-damaged, Parkinson's disease, and normal adult participants. Raters evaluated general intensity and amount of positive and negative facial emotion while participants were producing monologues regarding pleasant and unpleasant experiences. Social functioning items were derived from three standardized inventories. Overall, patient groups displayed more negative and less positive emotion than normals, and the schizophrenic and right-brain-damaged groups showed less intense expressions than normals. Correlational analyses suggested that the more intense the facial expressions, the better the social functioning, and that the more negative emotion displayed, the poorer the social functioning.

Lateralisation of perceptual processing of pro- and anti-social emotions displayed in chimeric faces

Previous studies using a restricted range of split field chimeric faces suggest that the processing of facial emotional expressions is a highly lateralised phenomenon. Two theories have emerged with regard to the role the two cerebral hemispheres play in this processing. The "right hemisphere" hypothesis (e.g. Borod, Koff, Lorch, & Nicholas, 1988) suggests that the right hemisphere plays a prominent role in the processing of both positive and negative facial expressions. In contrast, the "valence hypothesis" (e.g. Reuter-Lorenz & Davidson, 1981) proposes that, while the right hemisphere plays the major role in processing negative emotions, the left hemisphere has a special role for positive emotions. Using all six of the human "universal facial expressions" (Ekman &Friesen, 1971) we present evidence that, superimposed onto a left visual field advantage (right hemisphere specialisation) for emotional processing, there is a "left shift" (right visual field advantage) for pro- as opposed to anti-social expression. We propose that facial expressions that are likely to be related to approach for communicative purposes initiate a greater degree of left hemisphere involvement. As a consequence, we suggest that for future laterality studies, the six universal emotional expressions should be reconsidered using a pro- to anti-social dimension rather than positive and negative groupings.

Emotional facial paresis in temporal lobe epilepsy: its prevalence and lateralizing value

The selection of patients with medically refractory temporal lobe epilepsy (TLE) for surgery depends on the concordance of data from clinical, imaging and electroencephalographic evaluation. Though clinical examination is often normal, emotional facial paresis has been described in patients with TLE. Utilizing a well-characterized group of mesial TLE (MTLE) patients, who have achieved excellent seizure outcome following anterior temporal lobectomy with amygdalohippocampectomy (ATL), we investigated the prevalence, predictive value and associations of emotional facial paresis. When compared to 8 out of 50 control subjects (16%), 36 out of 50 MTLE patients (72%) exhibited unilateral emotional facial paresis; the difference was highly significant (P<0.0001). The presence of contralateral emotional facial paresis correctly predicted the side of ATL in 86.1% patients. The occurrence of emotional facial paresis was significantly associated with longer duration of epilepsy prior to ATL and left ATL. Our observations confirm that emotional facial parersis contralateral to the side of mesial temporal sclerosis (MTS) is a valuable localizing sign in correctly predicting the epileptogenic temporal lobe. We hypothesize that the presence of an intact right hemisphere and pathological changes more extensive than MTS may be required for emotional facial paresis to readily manifest.

Asymmetry in hand grip strength and fatigue in low- and high-hostile men

The present study examined the relationship between hostility level and cerebral hemispheric motor functioning of 70 left-cerebral dominant men. Using the Cook-Medley Hostility Scale, the subject group was divided into thirds: One-third (N = 23) were classified as low-hostile, one-third (N = 23) were classified as high-hostile, and the remainder (N = 24) were excluded from analysis. A hand dynamometer was used to assess hand grip strength, perseveration, and fatigue, as measures of hemispheric motor functioning. Results yielded a hand-by-hostility group interaction, which indicated that high-hostile men evidenced significantly less hand grip strength at the right hand and significantly greater hand grip strength at the left hand relative to low-hostile men. These results suggest that high-hostile men may experience relatively greater right-cerebral arousal relative to their low-hostile counterparts. In other results, both groups showed greater perseveration at the left hand than at the right hand. Both groups also showed significant fatigue across trials at both hands. Analysis also revealed a hand-by-trial interaction, indicating that the right hand fatigued more quickly than the left hand across trials. Resistance to fatigue at the left hand and overestimation or relative imprecision in motor movement at the left hand are discussed in terms of arousal theory. These results and others are cited as contributing inroads into distinguishing between the emotional problems of depression, anxiety, and hostility.

Processing of facial emotional expression: spatio-temporal data as assessed by scalp event-related potentials

Event-related potentials (ERPs) were recorded in 10 adult volunteers, who were asked to view pictures of faces with different emotional expressions, i.e. fear, happiness, disgust, surprise and neutral expression [Ekman, P. & Friesen, W.V. (1975). Pictures of Facial Affect. Consulting Psychologist Press, Palo Alto, CA]. ERPs were recorded during two different tasks with the same stimuli. Firstly, subjects were instructed to pay attention to the gender of the faces by counting males or females. Secondly, they had to focus on facial expressions by counting faces who looked surprised. The classical scalp 'face-related potentials', i.e. a vertex-positive potential and a bilateral temporal negativity, were recorded 150 ms after the stimulus onset. Significant differences were found, firstly between late-latency ERPs to emotional faces and to neutral faces, between 250 and 550 ms of latency and, secondly, among the ERPs to the different facial expressions between 550 and 750 ms of latency. These differences appeared only during the expression discrimination task, not during the gender discrimination task. Topographic maps of these differences showed a specific right temporal activity related to each emotional expression, some particularities being observed for each expression. This study provides new data concerning the spatio-temporal features of facial expression processing, particularly a late-latency activity related to specific attention to facial expressions.

Oral dyspraxia in inherited speech and language impairment and acquired dysphasia

Half of the members of the KE family suffer from an inherited verbal dyspraxia. The affected members of the family have a lasting impairment in phonology and syntax. They were given various tests of oral praxis to investigate whether their deficit extends to nonverbal movements. Performance was compared to adult patients with acquired nonfluent dysphasia, those with comparable right-hemisphere lesions, and age-matched controls. Affected family members and patients with nonfluent dysphasia were impaired overall at performing oral movements, particularly combinations of movements. It is concluded that affected members of the KE family resemble patients with acquired dysphasia in having difficulties with oral praxis and that speech and language problems of affected family members arise from a lower level disorder.

Differential limbic--cortical correlates of sadness and anxiety in healthy subjects: implications for affective disorders

BACKGROUND

Affective disorders are associated with comorbidity of depression and anxiety symptoms. Positron emission tomography resting-state studies in affective disorders have generally failed to isolate specific symptom effects. Emotion provocation studies in healthy volunteers have produced variable results, due to differences in experimental paradigm and instructions.

METHODS

To better delineate the neural correlates of sad mood and anxiety, this study used autobiographical memory scripts in eight healthy women to generate sadness, anxiety, or a neutral relaxed state in a within-subject design.

RESULTS

Sadness and anxiety, when contrasted to a neutral emotional state, engaged a set of distinct paralimbic-cortical regions, with a limited number of common effects. Sadness was accompanied by specific activations of the subgenual cingulate area (BA) 25 and dorsal insula, specific deactivation of the right prefrontal cortex BA 9, and more prominent deactivation of the posterior parietal cortex BAs 40/7. Anxiety was associated with specific activations of the ventral insula, the orbitofrontal and anterior temporal cortices, specific deactivation of parahippocampal gyri, and more prominent deactivation of the inferior temporal cortex BAs 20/37.

CONCLUSIONS

These findings are interpreted within a model in which sadness and anxiety are represented by segregated corticolimbic pathways, where a major role is played by selective dorsal cortical deactivations during sadness, and ventral cortical deactivations in anxiety.

The effects of age and gender on the perception of lexical emotion

The primary purpose of this study was to examine the perception of lexical/verbal emotion across the adult life span. Secondary goals were to examine the contribution of gender and valence (i.e., pleasantness/unpleasantness) to the processing of lexical emotional stimuli. Participants were 28 young (ages 20-39), 28 middle-aged (ages 40-59), and 28 older (ages 60-85) right-handed adults; there were 14 men and 14 women in each age group. Age groups were comparable on demographic and cognitive variables. Participants made accuracy judgments and intensity ratings of emotional (both positive and negative) and nonemotional stimuli from lexical perception tasks from the New York Emotion Battery (Borod, Welkowitz, & Obler, 1992). Accuracy and intensity measures were not significantly correlated. When age was examined, older participants perceived emotional and nonemotional lexical stimuli with significantly less accuracy than did younger and middle-aged participants. On the other hand, older participants evaluated the nonemotional lexical stimuli as significantly more intense than younger participants. When gender was examined, lexical stimuli were processed more accurately by female than male participants. Further, emotional stimuli were rated more intense by female participants. Clinical implications of these findings are discussed.

A preliminary evaluation of emotional experience and expression following unilateral brain damage

In this preliminary study, hemispheric specialization for the experience and expression of emotion was investigated. Subjects were right-brain-damaged (RBD), left-brain-damaged (LBD), and normal control (NC) right-handed adults, carefully matched on demographic and neurological variables. Facial expressions were videotaped while subjects described recollected emotional and nonemotional experiences. Expressions were later rated by trained judges for emotional intensity and category accuracy. To examine experience, subjects evaluated the intensity and accuracy with which they had produced their monologues. RBDs produced less intense facial expressions and reported less intense emotional experiences than LBDs and NCs. LBDs rated themselves as producing expressions with less accuracy than did RBDs and NCs. These findings are consistent with research that supports the right-hemisphere hypothesis for emotion. In addition, judges' ratings and subjects' self-reports of emotional intensity were positively correlated for normal but not for brain-damaged subjects.

Narrative discourse in children with early focal brain injury

Children with early brain damage, unlike adult stroke victims, often go on to develop nearly normal language. However, the route and extent of their linguistic development are still unclear, as is the relationship between lesion site and patterns of delay and recovery. Here we address these questions by examining narratives from children with early brain damage. Thirty children (ages 3:7-10:10) with pre- or perinatal unilateral focal brain damage and their matched controls participated in a storytelling task. Analyses focused on linguistic proficiency and narrative competence. Overall, children with brain damage scored significantly lower than their age-matched controls on both linguistic (morphological and syntactic) indices and those targeting broader narrative qualities. Rather than indicating that children with brain damage fully catch up, these data suggest that deficits in linguistic abilities reassert themselves as children face new linguistic challenges. Interestingly, after age 5, site of lesion does not appear to be a significant factor and the delays we have witnessed do not map onto the lesion profiles observed in adults with analogous brain injuries.

A neuropsychological model relating self-awareness to hostility

Neuropsychological advances may help researchers better understand the relationship between psychological constructs. This paper proposes a neuropsychological model explaining the negative relationship between hostility and "self-awareness," which has been suggested by previous research [H. A. Demaree and D. W. Harrison (1995a) "Behavioral, Physiological, and Neuropsychological Correlates of Hostility," manuscript submitted for publication; L. H. Epstein and P. A. Cluss (1982) "A Behavioral Medicine Perspective on Adherence to Long-Term Medical Regimes," Journal of Consulting and Clinical Psychology, Vol. 50, pp. 950-971; M. F. Scheier et al. (1974) "Self-Awareness and Physical Aggression," Journal of Experimental and Social Psychology, Vol. 10, pp. 254-273]. The authors review the role of the right cerebrum in both hostility and "self-awareness"--including arousal, perceptual, expressive, and integrative processes. Using identifiable tracts in the brain, the model suggests how deficits in "self-awareness"--poor awareness of physiological arousal, natural and emotional environment, etc.--may enhance the probability of hostility expression. This model is supported by previous empirical research and provides direction for future neuropsychological investigation.

Cerebral laterality in affect and affective illness: a review

It is generally claimed that affect processing is a right hemisphere function. It is also claimed that right hemisphere dysfunction is characteristic of depressive illness. These claims are not accepted without controversy, and it has been found that the relationship between affect processing and affective illness in terms of intra- and interhemispheric role is not straightforward. Two types of studies were reviewed in this context: behavioral and electrophysiological. Potential confounding effects are discussed.

Face and voice expression identification in patients with emotional and behavioural changes following ventral frontal lobe damage

Impairments in the identification of facial and vocal emotional expression were demonstrated in a group of patients with ventral frontal lobe damage who had socially inappropriate behaviour. The expression identification impairments could occur independently of perceptual impairments in facial recognition, voice discrimination, or environmental sound recognition. The face and voice expression problems did not necessarily occur together in the same patients, providing an indication of separate processing. Poor performance on both expression tests was correlated with the degree of alteration of emotional experience reported by the patients. There was also a strong positive correlation between the degree of altered emotional experience and the severity of the behavioural problems (e.g. disinhibition) found in these patients. A comparison group of patients with brain damage outside the ventral frontal lobe region, without these behavioural problems, was unimpaired on the face expression identification test, was significantly less impaired at vocal expression identification and reported little subjective emotional change. The expression identification deficits in ventral frontal patients may contribute to the abnormal behaviour seen after frontal lesions, and have implications for rehabilitation.

Affective facial expression in infants with focal brain damage

Children are fluent affective communicators by their first birthday. The development of affective facial expression in infants with focal brain damage thus provides a promising context in which to investigate the developing neural substrates of emotions. We examined both positive and negative affective expression in 12 infants (6-24 months) with pre- or perinatal unilateral focal brain damage (6RHD and 6LHD) and their age- and gender-matched controls. Infants were videotaped in free and semi-structured tasks. Interactions were microanalytically coded, including the use of FACS. Both normal and babies with posterior LHD exhibited the full range of appropriate affective expressions. In contrast, infants with posterior RHD showed marked affective impairment to positive, but not to negative simulation.

Perceiver and poser asymmetries in processing facial emotion

This study examined both perceiver and poser asymmetries in processing facial emotion. Posers were left brain-damaged (LBD), right brain-damaged (RBD), and normal control (NC) right-handed males videotaped while expressing happiness and anger. Perceivers rated the facial expressions for asymmetry in original and reversed orientations. Overall, expressions viewed in the reversed orientation were rated as more left-sided than in the original orientation. In the reversed orientation, the more extensive left hemiface of the NCs and LBDs fell in the perceiver's left hemispace. This finding is consistent with previous research demonstrating a left hemispace bias for free-field viewing of emotional faces. Expressions were produced significantly more intensely on the left than the right hemiface by NCs and LBDs; expressions of RBDs were not significantly lateralized.

Posed emotional expression in unilateral brain damaged patients

The facial expressions of six basic emotions were posed by two groups of right (N = 23) and left (N = 34) brain damaged patients and by a control group of normal subjects (N = 28). The posed expressions were examined by means of the Facial Action Coding System (FACS) which provides analytical and objective scoring, as by a subjective scale of appropriateness of expression. Results indicated no difference between controls and patients with a lesion in the right or left hemisphere. These findings are inconsistent with the hypothesis that the right hemisphere plays a specific role in the control of posed facial expression. No relationship was observed between posed emotional expressions and facial paralysis or the presence of oral apraxia.