Hemiface mobility and facial expression asymmetry

Posed versus spontaneous facial expressions are modulated by opposite cerebral hemispheres

Clinical research has indicated that the left face is more expressive than the right face, suggesting that modulation of facial expressions is lateralized to the right hemisphere. The findings, however, are controversial because the results explain, on average, approximately 4% of the data variance. Using high-speed videography, we sought to determine if movement-onset asymmetry was a more powerful research paradigm than terminal movement asymmetry. The results were very robust, explaining up to 70% of the data variance. Posed expressions began overwhelmingly on the right face whereas spontaneous expressions began overwhelmingly on the left face. This dichotomy was most robust for upper facial expressions. In addition, movement-onset asymmetries did not predict terminal movement asymmetries, which were not significantly lateralized. The results support recent neuroanatomic observations that upper versus lower facial movements have different forebrain motor representations and recent behavioral constructs that posed versus spontaneous facial expressions are modulated preferentially by opposite cerebral hemispheres and that spontaneous facial expressions are graded rather than non-graded movements.

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.

Processing of Facial Blends of Emotion: Support for Right Hemisphere Cognitive Aging

Clinical research on facial emotions has focused primarily on differences between right and left hemiface. Social psychology, however, has suggested that differences between upper versus lower facial displays may be more important, especially during social interactions. We demonstrated previously that upper facial displays are perceived preferentially by the right hemisphere, while lower facial displays are perceived preferentially by the left hemisphere. A marginal age-related effect was observed. The current research expands our original cohort to include 26 elderly individuals over age 62. Fifty-six, strongly right-handed, healthy, adult volunteers were tested tachistoscopically by flashing randomized facial displays of emotion to the right and left visual fields. The stimuli consisted of line drawings displaying various combinations of emotions on the upper and lower face. The subjects were tested under two conditions: without attend instruction and with instructions to attend to the upper face. Based on linear regression and discriminant analyses modeling age, subject performance could be divided into two distinct groups: Young (< 62 years) and Old (> 62 years). Without attend instructions, both groups robustly identified the emotion displayed on the lower face, regardless of visual field presentation. With instructions to attend to the upper face, the Old group demonstrated a markedly decreased ability to identify upper facial displays, compared to the Young group. The most significant difference was noted in the left visual field/right hemisphere. Our results demonstrate a significant decline in the processing of upper facial emotions by the right hemisphere in older individuals, thus providing partial support for the right hemisphere hypothesis of cognitive aging. The decreased ability to perceive upper facial displays coupled with age-related deficits in processing affective prosody may well cause impaired psychosocial competency in the elderly.

Digitizing the moving face during dynamic displays of emotion

Humans typically decode facial signals during dynamic interactions in which the face moves. In this study, we digitized real time video signals in order to examine movement asymmetries across the face during emotional and nonemotional expressions. Forty dextral males were tested. For each expression, a 400 ms video segment was analyzed for changes in signal value (pixel intensity) over consecutive frames. The upper and lower face regions were examined separately due to differences in the cortical enervation of facial muscles in the upper (bilateral) vs lower face (contralateral). Results revealed distinctly different movement asymmetries over the lower and upper hemiface. In the upper face, more movement occurred over the right side for most facial expressions, regardless of emotionality. The latter finding questions the assumption that muscles of the upper face are symmetrical and/or bilaterally enervated in a symmetrical manner. In the lower face, negative expressions linked to fight-flight emotions (i.e. fear, anger) were associated with greater left sided movement, whereas happiness tended to be associated with more right sided movement. No consistent pattern of movement asymmetry occurred for nonemotional expressions. Although the valence-related movement asymmetries in the lower face are consistent with neuropsychological models of emotional expressivity, it remains unclear whether they reflect activation or inhibitory hemispheric mechanisms. Taken together, these data suggest that multiple factors may contribute to expressive movement asymmetries of the face.

Factor analysis and the cerebral hemispheres: temporal, occipital and frontal functions

Three experiments are reported that use a number of lateralized tasks believed to draw on processes localized to the temporal, occipital or frontal lobes. Oblique factor analyses of the resultant asymmetries indicate the existence of nine lateralized functions, characterized as auditory lexical, facial figural, facial motive, spatial attentive, spatial positional, spatial quantitative, tactile figural, visual lexical, and visual phonetic in nature. Most functions are uncorrelated, but as in an earlier report (Boles, Neuropsychologia 29, 59-91, 1991), both positive and negative correlations are observed. These outcomes continue to be consistent with neurodevelopmental theory, and inconsistent with lateralization strength, hemisphericity, and independence views of individual differences in lateralization.

Mouth asymmetry upon repeating words. A controlled study of bipolarly depressive patients in the remitted euthymic state

In view of previous research concerning the lateral bias of hand movements accompanying speech, it was postulated that patients with bipolar depression should differ from normal controls with respect to the asymmetry of mouth opening when repeating speech sounds. This hypothesis was confirmed. Our patient group, consisting of 29 remitted euthymic out-patients, did not show the greater right-sided mouth opening characteristic of the gender-matched normal controls.

Spontaneous facial expression of emotions in brain-damaged patients

Spontaneous facial expression of emotion was studied in two groups of right (N = 23) and left (N = 39) brain-damaged patients and in a control group of normal subjects (N = 28). To elicit emotions four short movies, constructed to produce positive, negative or neutral emotional responses, were used. The method used to assess the facial expression of emotions was the Facial Action Coding System. Brain-damaged patients showed less facial responses to emotional stimuli than normal controls, but no difference was observed between subjects with right and left-sided lesions either with global or disaggregated data analyses, inconsistent with the hypothesis of a specialization of the right hemisphere for facial emotional expressions. An unexpected difference was observed in response to the unpleasant movie. Both normal controls and left brain-damaged patients often averted their gaze from the screen when unpleasant material was displayed, whereas right brain-damaged patients rarely showed gaze aversion. This finding suggests that the degree of emotional involvement or manner of coping with stressful input may be reduced as a result of right brain damage.

Left-sided oral asymmetries in spontaneous but not posed smiles

To investigate possible facial asymmetries during the production of posed and spontaneous smiles, the displacement of various reference points on the mouth were measured as subjects produced both kinds of smiles. Strobe cameras were used in combination with a computer-based analysis to record the smiles of left- and right-handed males and females. The analysis revealed that the left side of the mouth moved more than the right side during spontaneous but not posed smiles, supporting the notion that the right hemisphere may play a special role in emotional expression. This asymmetry was most apparent in left-handed females and right-handed males. These sex and handedness differences are discussed with reference to apparent inconsistencies in previous research on asymmetries in emotional expression.

The expression and perception of facial emotion in brain-damaged patients

This study examined the expression and perception of facial emotion in patients with unilateral cerebrovascular pathology. Subjects were 12 right brain-damaged (RBD), 15 left brain-damaged (LBD) aphasic, and 16 normal control (NC) right-handed males. Expressions were elicited during posed and spontaneous conditions. Both positive and negative emotions were studied. RBDs were significantly impaired, relative to LBDs and NCs, in expressing and perceiving facial emotion. There were no group differences as a function of condition, but there were differences as a function of emotional valence. Qualitative performance differences also were observed. There was no evidence that the ability to produce a particular emotion was related to the ability to identify the same emotion. Overall, these findings support the notion that the right cerebral hemisphere is dominant for expressing and perceiving facial emotion.