Facial mimicry is not modulated by dopamine D2/3 and opioid receptor antagonism

RATIONALE

According to theories of embodied cognition, facial mimicry - the spontaneous, low-intensity imitation of a perceived emotional facial expression - is first an automatic motor response, whose accompanying proprioceptive feedback contributes to emotion recognition. Alternative theoretical accounts, however, view facial mimicry as an emotional response to a rewarding stimulus, and/or an affiliative signal, and thus reject the view of an automatic motor copy.

OBJECTIVES

To contribute to this debate and further investigate the neural basis of facial mimicry, as well as its relation to reward processing, we measured facial reactions to dynamic happy and angry faces after pharmacologically manipulating the opioid and dopamine systems - respectively, thought to subserve 'liking' and 'wanting' of rewards.

METHODS

In a placebo-controlled, double-blind experiment, 130 volunteers received in a between-subjects design 50 mg of the opioidergic antagonist naltrexone, 400 mg of the dopaminergic antagonist amisulpride, or placebo.

RESULTS

Clear occurrence of facial mimicry, measured 4 h after drug intake with electromyography (EMG) of the zygomaticus major and corrugator supercilii muscles, was found. However, facial mimicry was not affected by either compound, as shown with both frequentist statistics, and a Bayesian asymptotic regression model.

CONCLUSIONS

This null finding does not support the hypothesis that facial mimicry (of happiness) reflects an emotional response to a rewarding stimulus, leaving open the possibility of facial mimicry being an automatic motor copy. The results are relevant to the discussion about the psychological nature and the neural basis of facial mimicry, although they should be considered preliminary, given the challenges of interpreting null findings when targeting a novel effect of unknown size.

Measurement of the N170 during facial neuromuscular electrical stimulation (fNMES)

BACKGROUND

Studies on facial feedback effects typically employ props or posed facial expressions, which often lack temporal precision and muscle specificity.

NEW METHOD

Facial Neuromuscular Electrical Stimulation (fNMES) allows for a controlled influence of contractions of facial muscles, and may be used to advance our understanding of facial feedback effects, especially when combined with Electroencephalography (EEG). However, electrical stimulation introduces significant interference that can mask underlying brain dynamics. Whether established signal processing methods can allow for a reduction of said interference whilst retaining effects of interest, remains unexplored.

RESULTS

We addressed these questions focusing on the classic N170 visual evoked potential, a face-sensitive brain component: 20 participants viewed images of houses, and of sad, happy, and neutral faces. On half of the trials, fNMES was delivered to bilateral lower-face muscles during the presentation of visual stimuli. A larger N170 amplitude was found for faces relative to houses. Interestingly, this was the case both without and during fNMES, regardless of whether the fNMES artefact was removed or not. Moreover, sad facial expressions elicited a larger N170 amplitude relative to neutral facial expressions, both with and without fNMES.

COMPARISON WITH EXISTING METHODS

fNMES offers a more precise way of manipulating proprioceptive feedback from facial muscles, which affords greater diversity in experimental design for studies on facial feedback effects.

CONCLUSIONS

We show that the combining of fNMES and EEG can be achieved and may serve as a powerful means of exploring the impact of controlled proprioceptive inputs on various types of cognitive processing.

Facial expression and emotion

Human facial expressions are unique in their ability to express our emotions and communicate them to others. The mimic expression of basic emotions is very similar across different cultures and has also many features in common with other mammals. This suggests a common genetic origin of the association between facial expressions and emotion. However, recent studies also show cultural influences and differences. The recognition of emotions from facial expressions, as well as the process of expressing one's emotions facially, occurs within an extremely complex cerebral network. Due to the complexity of the cerebral processing system, there are a variety of neurological and psychiatric disorders that can significantly disrupt the coupling of facial expressions and emotions. Wearing masks also limits our ability to convey and recognize emotions through facial expressions. Through facial expressions, however, not only "real" emotions can be expressed, but also acted ones. Thus, facial expressions open up the possibility of faking socially desired expressions and also of consciously faking emotions. However, these pretenses are mostly imperfect and can be accompanied by short-term facial movements that indicate the emotions that are actually present (microexpressions). These microexpressions are of very short duration and often barely perceptible by humans, but they are the ideal application area for computer-aided analysis. This automatic identification of microexpressions has not only received scientific attention in recent years, but its use is also being tested in security-related areas. This article summarizes the current state of knowledge of facial expressions and emotions.

Degenerate pathway for processing smile and other emotional expressions in congenital facial palsy: an hdEEG investigation

Influential theoretical models argue that an internal simulation mechanism (motor or sensorimotor simulation) supports the recognition of facial expressions. However, despite numerous converging sources of evidence, recent studies testing patients with congenital facial palsy (i.e. Moebius syndrome) seem to refute these theoretical models. However, these results do not consider the principles of neuroplasticity and degeneracy that could support the involvement of an alternative neural processing pathway in these patients. In the present study, we tested healthy participants and participants with Moebius syndrome in a highly sensitive facial expression discrimination task and concomitant high-density electroencephalographic recording. The results, both at the scalp and source levels, indicate the activation of two different pathways of facial expression processing in healthy participants and participants with Moebius syndrome, compatible, respectively, with a dorsal pathway that includes premotor areas and a ventral pathway. Therefore, these results support the reactivation of sensorimotor representations of facial expressions (i.e. simulation) in healthy subjects, in the place of an alternative processing pathway in subjects with congenital facial palsy.

This article is part of the theme issue ‘Cracking the laugh code: laughter through the lens of biology, psychology and neuroscience’.

Is There a Difference in Facial Emotion Recognition after Stroke with vs. without Central Facial Paresis?

The Facial Feedback Hypothesis (FFH) states that facial emotion recognition is based on the imitation of facial emotional expressions and the processing of physiological feedback. In the light of limited and contradictory evidence, this hypothesis is still being debated. Therefore, in the present study, emotion recognition was tested in patients with central facial paresis after stroke. Performance in facial vs. auditory emotion recognition was assessed in patients with vs. without facial paresis. The accuracy of objective facial emotion recognition was significantly lower in patients with vs. without facial paresis and also in comparison to healthy controls. Moreover, for patients with facial paresis, the accuracy measure for facial emotion recognition was significantly worse than that for auditory emotion recognition. Finally, in patients with facial paresis, the subjective judgements of their own facial emotion recognition abilities differed strongly from their objective performances. This pattern of results demonstrates a specific deficit in facial emotion recognition in central facial paresis and thus provides support for the FFH and points out certain effects of stroke.

Facial Emotion Recognition in Patients with Post-Paralytic Facial Synkinesis—A Present Competence

Facial palsy is a movement disorder with impacts on verbal and nonverbal communication. The aim of this study is to investigate the effects of post-paralytic facial synkinesis on facial emotion recognition. In a prospective cross-sectional study, we compared facial emotion recognition between n = 30 patients with post-paralytic facial synkinesis (mean disease time: 1581 ± 1237 days) and n = 30 healthy controls matched in sex, age, and education level. Facial emotion recognition was measured by the Myfacetraining Program. As an intra-individual control condition, auditory emotion recognition was assessed via Montreal Affective Voices. Moreover, self-assessed emotion recognition was studied with questionnaires. In facial as well as auditory emotion recognition, on average, there was no significant difference between patients and healthy controls. The outcomes of the measurements as well as the self-reports were comparable between patients and healthy controls. In contrast to previous studies in patients with peripheral and central facial palsy, these results indicate unimpaired ability for facial emotion recognition. Only in single patients with pronounced facial asymmetry and severe facial synkinesis was an impaired facial and auditory emotion recognition detected. Further studies should compare emotion recognition in patients with pronounced facial asymmetry in acute and chronic peripheral paralysis and central and peripheral facial palsy.

MODULATION EFFECT OF MOTOR ACTIVITY ON LIMBIC AREAS: AN FMRI STUDY

Neural activation of the motor cortex has been consistently reported to be evoked in the emotion processing of facial expressions, but it is poorly understood whether and how the motor system influences the activity of limbic areas during participants’ perceived emotional expressions. In this study, we proposed that motor activations evoked by emotional processing influence the activations in limbic areas such as amygdala during the perception of facial expressions. To examine this issue, a masked priming paradigm was adopted in our fMRI experiment, which could modulate the activation within the motor cortex when healthy participants perceived sad or happy facial expressions. We found that the first presented stimulus (masked prime) in each trial reduced the activations in the premotor cortex and inferior frontal gyrus when the movement of facial muscles implied by the arrows on the prime stimulus was consistent with that implied by the target face expressions (compatible condition), but increased the activations in these two areas when the movements implied by the arrows and the target face expressions were inconsistent (incompatible condition). The superior temporal gyrus, middle cingulate gyrus and amygdala also showed similar response tendency to that in motor cortex. Moreover, psychophysiological interaction (PPI) analysis showed that both right middle cingulate gyrus and bilateral superior temporal gyrus were closely linked to the premotor cortex with inferior frontal gyrus during the incompatible trials compared with the compatible trials. Together with this result and the significant activation correlations between the motor cortex and the limbic areas, this work revealed the modulation effect of motor cortex on brain regions related to emotion perception, suggesting that motor representation of facial movements can affect emotion experience. Our results provide new evidence for the functional role of motor system in the perception of facial emotions, and could contribute to the understanding of the deficit in social interaction for patients with autism or schizophrenia.

Perceptions of Patients with Facial Paralysis: Predicting Social Implications and Setting Goals

The goal of this article is to better understand the social impact of facial paralysis. Patients with facial paralysis may suffer from impaired social interactions, disruption of self-concept, psychological distress, and decreased overall quality of life. Vigilance in detecting patients suffering from mental health issues may result in providing early referral for psychological evaluation and psychosocial support resources complementing facial reanimation treatment.

Cosmetic appreciation and emotional processing in patients with a peripheral facial palsy: A systematic review

Background; The goal of this review is 1) to summarize the studies assessing PFP by casual observers, patients themselves and the cosmetic appreciation of the PFP and 2) to summarize the studies assessing whether there is a difference in emotional recognition/processing of facial emotions and/or cognitive tasks in patients with a PFP. Materials and Methods; A multi-database systematic literature search was performed using the following databases: Pubmed, Embase, Medline, and The Cochrane Library from the earliest date of each database up to December 2019. Population of interest consisted of patients with a PFP and studies that investigated cosmetic appreciation and/or emotional recognition and/or emotional processing in these patients. Two authors rated the methodological quality of the included studies independently using the 'Newcastle - Ottawa Quality Assessment Scale' for nonrandomised studies' (NOS). Two authors extracted the outcome data regarding cosmetic appreciation and/or emotional recognition/processing from the included studies. Results; Twelve hundred and thirty-two studies were found of which eleven studies met the inclusion criteria. Most studies were assessed to be of 'fair' to 'good' methodological quality. The Cohen's kappa (between author RL and SP) was 0.68. Two studies investigated emotional processing and/or emotional recognition. Nine studies investigated cosmetic appreciation in both patients and casual observers. Important findings of this systematic review are that there is a correlation between the perceived severity of the PFP of the patients and the ratings by casual observers. Secondly there seems to be a laterality difference in cosmetic appreciation and thirdly there might to be a decreased emotional recognition and processing in patients with a PFP. Conclusion; Emotional recognition and cosmetic appreciation in patients with a PFP is an under investigated area, in which further studies are needed to substantiate the findings in current literature.

Altering sensorimotor simulation impacts early stages of facial expression processing depending on individual differences in alexithymic traits

Simulation models of facial expressions suggest that posterior visual areas and brain areas underpinning sensorimotor simulations might interact to improve facial expression processing. According to these models, facial mimicry, a manifestation of sensorimotor simulation, may contribute to the visual processing of facial expressions by influencing early stages. The aim of this study was to assess whether and how sensorimotor simulation influences early stages of face processing, also investigating its relationship with alexithymic traits given that previous studies have suggested that individuals with high levels of alexithymic traits (vs. individuals with low levels of alexithymic traits) tend to use sensorimotor simulation to a lesser extent. We monitored P1 and N170 ERP components of the event-related potentials (ERP) in participants performing a fine discrimination task of facial expressions and animals, as a control condition. In half of the experiment, participants could freely use their facial mimicry whereas in the other half they had their facial mimicry blocked by a gel. Our results revealed that only individuals with lower compared to high alexithymic traits showed a larger modulation of the P1 amplitude as a function of the mimicry manipulation selectively for facial expressions (but not for animals), while we did not observe any modulation of the N170. Given the null results at the behavioural level, we interpreted the P1 modulation as compensative visual processing in individuals with low levels of alexithymia under conditions of interference on the sensorimotor processing, providing a preliminary evidence in favor of sensorimotor simulation models.

Cross-Cultural and Environmental Influences on Facial Emotional Discrimination Sensitivity in 9-Year-Old Children from Swiss and Vietnamese Schools

Abstract. The Other Race Effect (ORE), i.e., recognition facilitation for own-race faces, is a well-established phenomenon with broad evidence in adults and infants. Nevertheless, the ORE in older children is poorly understood, and even less so for emotional face processing. This research samples 87 9-year-old children from Vietnamese and Swiss schools. In two separate studies, we evaluated the children’s abilities to perceive the disappearance of emotions in Asian and Caucasian faces in an offset task. The first study evaluated an “emotional ORE” in Vietnamese-Asian, Swiss-Caucasian, and Swiss-Multicultural children. Offset times showed an emotional ORE in Vietnamese-Asian children living in an ethnically homogeneous environment, whereas mixed ethnicities in Swiss children seem to have balanced performance between face types. The second study compared socioemotionally trained versus untrained Vietnamese-Asian children. Vietnamese children showed a strong emotional ORE and tend to increase their sensitivity to emotion offset after training. Moreover, an effect of emotion consistent with previous observation in adults could suggest a cultural sensitivity to disapproval signs. Taken together, the results suggest that 9-year-old children can present an emotional ORE, but that a heterogeneous environment or an emotional training could strengthen face-processing abilities without reducing skills on their own-group.

Assessing anxiety, depression and quality of life in patients with peripheral facial palsy: a systematic review

Objective

Peripheral facial palsy (PFP) is predominantly a unilateral disorder of the facial nerve, which can lead to psychological disorders that can result in decreased quality of life. The aim of this systematic review was to assess anxiety, depression and quality of life symptoms associated with PFP.

Data sources

We searched the Medline, PEDro, CINAHL and Google Scholar databases to conduct this systematic review while following Preferred Reporting Items for Systematic Reviews and Meta-Analyses standards. The search was performed by two independent reviewers, and differences between the two reviewers were resolved by consensus.

Study Selection

The search terms used were derived from the combination of the following MeSH terms: "facial paralysis", "bell palsy", "anxiety", "anxiety disorders", "depression", "depressive disorders", "quality of life" and not MeSH: "facial palsy", "hemifacial paralysis", "facial paresis", "Peripheral Facial Paralysis", using the combination of different Boolean operators (AND/OR).

Data Extraction

On November 1st (2019).

Data Synthesis

In total, 18 cross-sectional articles and two case-control studies were selected.

Conclusions

The cross-sectional articles showed low methodological quality, while the case-control studies showed acceptable methodological quality. Limited evidence suggests that patients with PFP might have increased levels of anxiety and depressive symptoms. A qualitative analysis also showed limited evidence that quality of life might be diminished in patients with PFP.

PROSPERO

CRD42020159843.

Lateralization of facial emotion processing and facial paresis in Vestibular Schwannoma patients

OBJECTIVE

This study investigates whether there exist differences in lateralization of facial emotion processing in patients suffering from Vestibular Schwannoma (VS) based on the presence of a facial paresis and their degree of facial functioning as measured by the House Brackmann Grading scale (HBG).

METHODS

Forty-four VS patients, half of them with a facial paresis and half of them without a facial paresis, rated how emotive they considered images of faces showing emotion in the left versus right visual field. Stimuli consisted of faces with a neutral half and an emotional (happy or angry) half. The study had a mixed design with emotional expression (happy vs. angry) and emotional half (left vs. right visual field) of the faces as repeated measures, and facial paresis (present vs. absent) and HBG as between subjects' factors. The visual field bias was the main dependent variable.

RESULTS

In line with typical findings in the normal population, a left visual field bias showed in the current sample: patients judged emotional expressions shown in the left visual field as more emotive than those shown in the right visual field. No differences in visual field bias showed based on the presence of a facial paresis nor based on patients' HBG.

CONCLUSION

VS patients show a left visual field bias when processing facial emotion. No differences in lateralization showed based on the presence of a facial paresis or on patients' HBG. Based on this study, facial paresis thus does not affect the lateralization of facial emotion processing in patients with VS.

Facial Clinimetric Evaluation Scale and Synkinesis Assessment Questionnaire Translation into Brazilian Portuguese: A Validation Study

Introduction  Facial nerve palsy results in both functional disability and psychological morbidity. There are several well-established grading scales to quantify the quality of life of these patients.

Objective  Translate and validate the Facial Clinimetric Evaluation (FaCE) scale and Synkinesis Assessment Questionnaire (SAQ) to Brazilian Portuguese.

Methods  This study adopted a forward-backward translation method and performed cross-cultural adaptation. A pilot study was conducted to correct any confusing language and to evaluate content validity. A validation study was then performed. Internal consistency of the Brazilian Portuguese version of the FaCE and SAQ items was evaluated by Cronbach’s alpha coefficient. Construct validity was assessed by Spearman’s Rank Correlation Coefficient between FaCE and SAQ scores to eFACE, House-Brackmann, Short Form 12 (SF-12) and Facial Disability Index (FDI) (sub)scores.

Results  A total of 90 patients were included. Cronbach’s alpha for total domain scored 0.881 for FaCE and 0.809 for SAQ. FaCE total score correlation to eFACE total and House-Brackmann showed Spearman’s r value of 0.537 and −0.538, respectively ( p  < 0.001). SAQ correlation to eFACE synkinesis subdomain was −0.449 ( p  < 0.001). No correlation was found between SAQ and HB score. FaCE total score correlations were of 0.301 and 0.547 for SF-12 PCS and MCS, respectively ( p  < 0.001). Correlation between FaCE total and FDI Physical and Social/well-being functions were 0.498 and 0.567 ( p  < 0.001).

Conclusion  Brazilian Portuguese FaCE scale and SAQ versions achieved high validity and reliability in the present study. These translated instruments demonstrated good psychometric properties, being proper to use in clinical practice in Brazil and with Brazilian Portuguese speakers.

Lateralization of facial emotion processing and facial mimicry

The two halves of the brain are believed to play different roles in emotional processing. In studies involving chimeric faces, emotional expressions in the left visual field are more strongly perceived as emotional than those in the right visual field. Notably, the role of facial mimicry has not been studied in relation to hemispheric lateralization. In the current study, which used a novel stimulus set of chimeric faces, we proposed and found that emotional intensity judgments replicate the left visual field bias for facial expressions of emotions. While a general facial mimicry effect to the chimeric faces occurred for the corrugator muscle, these mimicry effects were not related to the visual field bias. The results suggest that encoding the emotionality of another person's facial expression might occur independent from the mere mimicry of the facial expression itself.

Children with facial paralysis due to Moebius syndrome exhibit reduced autonomic modulation during emotion processing

BACKGROUND

Facial mimicry is crucial in the recognition of others' emotional state. Thus, the observation of others' facial expressions activates the same neural representation of that affective state in the observer, along with related autonomic and somatic responses. What happens, therefore, when someone cannot mimic others' facial expressions?

METHODS

We investigated whether psychophysiological emotional responses to others' facial expressions were impaired in 13 children (9 years) with Moebius syndrome (MBS), an extremely rare neurological disorder (1/250,000 live births) characterized by congenital facial paralysis. We inspected autonomic responses and vagal regulation through facial cutaneous thermal variations and by the computation of respiratory sinus arrhythmia (RSA). These parameters provide measures of emotional arousal and show the autonomic adaptation to others' social cues. Physiological responses in children with MBS were recorded during dynamic facial expression observation and were compared to those of a control group (16 non-affected children, 9 years).

RESULTS

There were significant group effects on thermal patterns and RSA, with lower values in children with MBS. We also observed a mild deficit in emotion recognition in these patients.

CONCLUSION

Results support "embodied" theory, whereby the congenital inability to produce facial expressions induces alterations in the processing of facial expression of emotions. Such alterations may constitute a risk for emotion dysregulation.

Neural measures of the causal role of observers' facial mimicry on visual working memory for facial expressions

Simulation models of facial expressions propose that sensorimotor regions may increase the clarity of facial expressions representations in extrastriate areas. We monitored the event-related potential marker of visual working memory (VWM) representations, namely the sustained posterior contralateral negativity (SPCN), also termed contralateral delay activity, while participants performed a change detection task including to-be-memorized faces with different intensities of anger. In one condition participants could freely use their facial mimicry during the encoding/VWM maintenance of the faces while in a different condition participants had their facial mimicry blocked by a gel. Notably, SPCN amplitude was reduced for faces in the blocked mimicry condition when compared to the free mimicry condition. This modulation interacted with the empathy levels of participants such that only participants with medium-high empathy scores showed such reduction of the SPCN amplitude when their mimicry was blocked. The SPCN amplitude was larger for full expressions when compared to neutral and subtle expressions, while subtle expressions elicited lower SPCN amplitudes than neutral faces. These findings provide evidence of a functional link between mimicry and VWM for faces and further shed light on how this memory system may receive feedbacks from sensorimotor regions during the processing of facial expressions.

Outcomes of large vestibular schwannomas following subtotal resection: early post-operative volume regression and facial nerve function

INTRODUCTION

Subtotal resection (STR) of vestibular schwannoma (VS) tumors remains controversial and little is known regarding post-operative volume changes.

METHODS

Authors retrospective reviewed the medical records from January 1st 2002 to January 1st 2018, for all patients who had undergone primary STR of large VS at a single tertiary academic institution.

RESULTS

Our series consists of 34 patients with a mean age of 53.9 (median 53; range 21-87) years that had STR of their VS tumor. The mean pre-operative tumor diameter and volume was 3.9 cm (median 3.0 cm; range 1.6-6.0 cm) and 11.7 cm³ (median 9.6 cm³; range 2.8-44.3 cm³), respectively, with a mean extent of resection of 86% (median 90%; range 53-99%). The mean radiographic and clinical follow-up was 40 months (range 6-120 months) and 51 months (range 7-141 months), respectively. 85% of patients had optimal House-Brackmann (HB) scores (Grade 1 & 2) immediately post-operatively, and 91% at 1 year; 94% of patients had normal (HB 1) at last follow-up. There was significant regression of residual tumor volume at 1 year (p = 0.006) and 2 years (p = 0.02), but not at 3 years (p = 0.08), when compared to the prior year. There was significant regression of size over time, with a mean slope estimate of - 0.70 units per year (p < 0.001).

CONCLUSION

Excellent clinical facial nerve outcomes can be obtained with STR of large VS tumors. Maximal reduction in tumor size occurs at 2-year post-operatively. Thus, in patients undergoing surgery for large VS, STR and a "watch and wait" strategy is a reasonable treatment option that may optimize facial nerve outcomes.

Give me a kiss! An integrative rehabilitative training program with motor imagery and mirror therapy for recovery of facial palsy

BACKGROUND

Peripheral facial nerve palsy (FNP) can have various causes, such as Bell's palsy or after surgery for acoustic neuroma. Rehabilitation is often required but there is no evidence that any rehabilitation approach is more efficacious than another.

AIM

The purpose of this research was to determine the effects of neurocognitive-rehabilitative approach through mirror-therapy (MT) and motor-imagery (MI), integrated into the traditional rehabilitation with mime-therapy and myofascial-approach.

DESIGN

This study was designed as a double-blind, randomized, controlled trial.

SETTING

This study took place from January 2016 to June 2018 at the Unit of Physical Medicine and Rehabilitation of Umberto I Polyclinic Hospital, Rome, Italy.

POPULATION

Twenty-two patients were randomized into two groups: the mirror therapy group (N.=11, MT and MI) and the traditional rehabilitation group (N.=11, mime-therapy and a myofascial-approach).

METHODS

Outcome assessments were performed before treatment (T0), after one month (T1=10 session, twice/week), after the second and third months (T2=10 twice/week + 5 of MT+MI one/week and T3=10 twice/week + 5 of MT+MI 1/week), and at the 4-week follow-up (T4=2 months follow-up).

RESULTS

The analysis of the functional evaluations show that both groups experienced progressive improvement T0 to T3, with stabilization of the results at the follow-up. There was a significant difference in House-Brackmann-Scale scores between T0 and follow-up in favor of the experimental group. In terms of quality of life (FaCE scale), total scores and social function items improved in both groups from T0 to T3. The experimental group obtained better results with regard to quality of life and emotional depression.

CONCLUSIONS

The integrated use of MT and MI is efficacious in the rehabilitation of FNP, improving facial physical function. Further studies are needed to determine the predictive factors of the recovery of facial mimic.

CLINICAL REHABILITATION IMPACT

The ability of patients with unilateral facial paralysis to recognize and appropriately judge facial expressions and perceive the judgments of others remains underexplored. The likelihood of recovering near-normal facial-function after grade VI facial paralysis is low. Procedures, such as the immediate repair of the facial nerve with an interposed donor graft, might improve facial function in patients with partially injured facial nerves.

Congenital facial palsy and emotion processing: The case of Moebius syndrome

According to the Darwinian perspective, facial expressions of emotions evolved to quickly communicate emotional states and would serve adaptive functions that promote social interactions. Embodied cognition theories suggest that we understand others' emotions by reproducing the perceived expression in our own facial musculature (facial mimicry) and the mere observation of a facial expression can evoke the corresponding emotion in the perceivers. Consequently, the inability to form facial expressions would affect the experience of emotional understanding. In this review, we aimed at providing account on the link between the lack of emotion production and the mechanisms of emotion processing. We address this issue by taking into account Moebius syndrome, a rare neurological disorder that primarily affects the muscles controlling facial expressions. Individuals with Moebius syndrome are born with facial paralysis and inability to form facial expressions. This makes them the ideal population to study whether facial mimicry is necessary for emotion understanding. Here, we discuss behavioral ambiguous/mixed results on emotion recognition deficits in Moebius syndrome suggesting the need to investigate further aspects of emotional processing such as the physiological responses associated with the emotional experience during developmental age.

A Quantitative Assessment of Lip Movements in Different Facial Expressions Through 3-Dimensional on 3-Dimensional Superimposition: A Cross-Sectional Study

PURPOSE

The quantitative assessment of facial modifications from mimicry is of relevant interest for the rehabilitation of patients who can no longer produce facial expressions. This study investigated a novel application of 3-dimensional on 3-dimensional superimposition for facial mimicry.

MATERIALS AND METHODS

This cross-sectional study was based on 10 men 30 to 40 years old who underwent stereophotogrammetry for neutral, happy, sad, and angry expressions. Registration of facial expressions on the neutral expression was performed. Root mean square (RMS) point-to-point distance in the labial area was calculated between each facial expression and the neutral one and was considered the main parameter for assessing facial modifications. In addition, effect size (Cohen d) was calculated to assess the effects of labial movements in relation to facial modifications.

RESULTS

All participants were free from possible facial deformities, pathologies, or trauma that could affect facial mimicry. RMS values of facial areas differed significantly among facial expressions (P = .0004 by Friedman test). The widest modifications of the lips were observed in happy expressions (RMS, 4.06 mm; standard deviation [SD], 1.14 mm), with a statistically relevant difference compared with the sad (RMS, 1.42 mm; SD, 1.15 mm) and angry (RMS, 0.76 mm; SD, 0.45 mm) expressions. The effect size of labial versus total face movements was limited for happy and sad expressions and large for the angry expression.

CONCLUSION

This study found that a happy expression provides wider modifications of the lips than the other facial expressions and suggests a novel procedure for assessing regional changes from mimicry.

Spontaneous Facial Actions Map onto Emotional Experiences in a Non-social Context: Toward a Component-Based Approach

While numerous studies have examined the relationships between facial actions and emotions, they have yet to account for the ways that specific spontaneous facial expressions map onto emotional experiences induced without expressive intent. Moreover, previous studies emphasized that a fine-grained investigation of facial components could establish the coherence of facial actions with actual internal states. Therefore, this study aimed to accumulate evidence for the correspondence between spontaneous facial components and emotional experiences. We reinvestigated data from previous research which secretly recorded spontaneous facial expressions of Japanese participants as they watched film clips designed to evoke four different target emotions: surprise, amusement, disgust, and sadness. The participants rated their emotional experiences via a self-reported questionnaire of 16 emotions. These spontaneous facial expressions were coded using the Facial Action Coding System, the gold standard for classifying visible facial movements. We corroborated each facial action that was present in the emotional experiences by applying stepwise regression models. The results found that spontaneous facial components occurred in ways that cohere to their evolutionary functions based on the rating values of emotional experiences (e.g., the inner brow raiser might be involved in the evaluation of novelty). This study provided new empirical evidence for the correspondence between each spontaneous facial component and first-person internal states of emotion as reported by the expresser.

Face proprioception does not modulate access to visual awareness of emotional faces in a continuous flash suppression paradigm

An important question in neuroscience is which multisensory information, presented outside of awareness, can influence the nature and speed of conscious access to our percepts. Recently, proprioceptive feedback of the hand was reported to lead to faster awareness of congruent hand images in a breaking continuous flash suppression (b-CFS) paradigm. Moreover, a vast literature suggests that spontaneous facial mimicry can improve emotion recognition, even without awareness of the stimulus face. However, integration of visual and proprioceptive information about the face to date has not been tested with CFS. The modulation of visual awareness of emotional faces by facial proprioception was investigated across three separate experiments. Face proprioception was induced with voluntary facial expressions or with spontaneous facial mimicry. Frequentist statistical analyses were complemented with Bayesian statistics. No evidence of multisensory integration was found, suggesting that proprioception does not modulate access to visual awareness of emotional faces in a CFS paradigm.

Deficits in the Mimicry of Facial Expressions in Parkinson's Disease

Background: Humans spontaneously mimic the facial expressions of others, facilitating social interaction. This mimicking behavior may be impaired in individuals with Parkinson's disease, for whom the loss of facial movements is a clinical feature.

Objective: To assess the presence of facial mimicry in patients with Parkinson's disease.

Method: Twenty-seven non-depressed patients with idiopathic Parkinson's disease and 28 age-matched controls had their facial muscles recorded with electromyography while they observed presentations of calm, happy, sad, angry, and fearful emotions.

Results: Patients exhibited reduced amplitude and delayed onset in the zygomaticus major muscle region (smiling response) following happy presentations (patients M = 0.02, 95% confidence interval [CI] −0.15 to 0.18, controls M = 0.26, CI 0.14 to 0.37, ANOVA, effect size [ES] = 0.18, p < 0.001). Although patients exhibited activation of the corrugator supercilii and medial frontalis (frowning response) following sad and fearful presentations, the frontalis response to sad presentations was attenuated relative to controls (patients M = 0.05, CI −0.08 to 0.18, controls M = 0.21, CI 0.09 to 0.34, ANOVA, ES = 0.07, p = 0.017). The amplitude of patients' zygomaticus activity in response to positive emotions was found to be negatively correlated with response times for ratings of emotional identification, suggesting a motor-behavioral link (r = –0.45, p = 0.02, two-tailed).

Conclusions: Patients showed decreased mimicry overall, mimicking other peoples' frowns to some extent, but presenting with profoundly weakened and delayed smiles. These findings open a new avenue of inquiry into the “masked face” syndrome of PD.