Sestito M., Umiltà M.A., Gallese V., et al. (2013) Facial reactions in response to dynamic emotional stimuli in different modalities in patients suffering from Schizophrenia: a behavioral and EMG study. Frontiers in Human Neuroscience, 7, 00368

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Sestito M., Umiltà M.A., Gallese V., et al. (2013) Facial reactions in response to dynamic emotional stimuli in different modalities in patients suffering from Schizophrenia: a behavioral and EMG study. Frontiers in Human Neuroscience, 7, 00368, doi:
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  ORIGINAL RESEARCH ARTICLE published: 23 July 2013doi: 10.3389/fnhum.2013.00368 Facial reactions in response to dynamic emotional stimuliin different modalities in patients suffering fromschizophrenia: a behavioral and EMG study Mariateresa Sestito  1 *,Maria Alessandra Umiltà  1 , Giancarlo De Paola  2  , Renata Fortunati  2  ,Andrea Raballo  3  , Emanuela Leuci  2  , Simone Maffei  2  ,Matteo Tonna  2  , Mario Amore  4  , Carlo Maggini  2  and Vittorio Gallese  1 *  1 Unit of Physiology, Department of Neuroscience, University of Parma, Parma, Italy  2  Psychiatric Division, Department of Neuroscience, University of Parma, Parma, Italy  3  Department of Mental Health, AUSL of Reggio Emilia, Reggio Emilia, Italy  4  Psychiatric Division, Department of Neuroscience, University of Genova, Genova, Italy  Edited by:  Martin Klasen, RWTH AachenUniversity, Germany  Reviewed by:  Giuliana Lucci, IRCCS Santa Lucia of Rome, Italy Lindsay M. Oberman, University of California, San Diego, USA *Correspondence:  Mariateresa Sestito, Unit of Physiology, Department of Neuroscience, University of Parma,Via Volturno 39, I-43100, Parma, Italy e-mail: mariateresa.sestito@ nemo.unipr.it; Vittorio Gallese, Section of Physiology, Department of Neuroscience, University of Parma,Via Volturno 39, I-43100, Parma, Italy e-mail: vittorio.gallese@unipr.it  Emotional facial expression is an important low-level mechanism contributing to theexperience of empathy, thereby lying at the core of social interaction. Schizophrenia isassociated with pervasive social cognitive impairments, including emotional processingof facial expressions. In this study we test a novel paradigm in order to investigate theevaluation of the emotional content of perceived emotions presented through dynamicexpressive stimuli, facial mimicry evoked by the same stimuli, and their functional relation.Fifteen healthy controls and 15 patients diagnosed with schizophrenia were presentedwith stimuli portraying positive (laugh), negative (cry) and neutral (control) emotionalstimuli in visual, auditory modalities in isolation, and congruently or incongruentlyassociated. Participants where requested to recognize and quantitatively rate theemotional value of the perceived stimuli, while electromyographic activity of Corrugatorand Zygomaticus muscles was recorded. All participants correctly judged the perceivedemotional stimuli and prioritized the visual over the auditory modality in identifying theemotion when they were incongruently associated (Audio-Visual Incongruent condition).The neutral emotional stimuli did not evoke any muscle responses and were judged byall participants as emotionally neutral. Control group responded with rapid and congruentmimicry to emotional stimuli, and in Incongruent condition muscle responses were drivenby what participants saw rather than by what they heard. Patient group showed a similarpattern only with respect to negative stimuli, whereas showed a lack of or a non-specificZygomaticus response when positive stimuli were presented. Finally, we found that onlypatients with reduced facial mimicry (Internalizers) judged both positive and negativeemotions as significantly more neutral than controls. The relevance of these findings forstudying emotional deficits in schizophrenia is discussed. Keywords: EMG, emotions, empathy, facial mimicry, schizophrenia, simulation INTRODUCTION Emotional expressions are widely acknowledged as essential incommunicating internal feelings and intentions (Ekman andOster,1979). The ability to communicate and understand theemotional states of others and their intentions is a fundamen-tal social skill. Indeed, facial expressions are among the mostcommon and significant emotion stimuli.To this end, it is well-known that humans react to emotionalfacial expressions with specific, congruent facial muscle mimicry,which can be reliably measured by electromyography (EMG; e.g.,Dimberg,1982,1988). For example, pictures of sad facial expres- sions evoke increased muscle Corrugator Supercilii activity, whilepictures of happy facial expressions increase muscle Zygomaticus Major  activity and decrease muscle Corrugator Supercilii activity (Lundqvist and Dimberg,1995;Han et al.,2012). These facial muscular reactions appear to be spontaneous and automatic(Dimbergand Thunberg,1998;Dimberget al.,2000,2002;Larsen et al.,2003). Many studies demonstrated that facial mimicry con-tributes to recognition of specific facial expressions (for a review,seeGoldman and Sripada,2005;Niedenthal et al.,2010). Indeed, blocking facial mimicry impairs recognition of facial expressionof emotions (Oberman et al.,2007). Furthermore, it has been proposed that mimicry reflects internal embodied simulationof the perceived facial expression in order to facilitate under-standing of its emotional meaning (Gallese,2003,2005,2006; Niedenthal,2007;Halberstadtet al.,2009;Niedenthal et al.,2009) and promoting empathy by means one’s facial feedback system(for a review of the facial feedback hypothesis, seeAdelmannand Zajonc,1989). A recent EMG study (Dimberg et al.,2011) showed that high empathic people, with respect to low empathic Frontiers in Human Neurosciencewww.frontiersin.org July 2013 | Volume 7 | Article 368 | 1  Sestito et al. Facial EMG responses in patients with schizophrenia group, are particularly sensitive in reacting with facial reactionswhen they look to emotional facial expressions. Moreover, highempathic people rated perceived facial emotional expressions asmore intense with respect to low empathic ones.Historically, affective features of schizophrenia were con-sidered an integral part of the disorder.Bleuler (1950)con- sidered affective disturbance to be a fundamental symptomof schizophrenia, whereas hallucinations and delusions wereregarded as accessory symptoms. Studies on patients’ facialmimicry in response to emotional stimuli showed that they acti-vate the same muscle of control subjects, but such activation wasfound to be weaker in patients than in healthy controls (Earnstet al.,1996;Kring and Earnst,1999). Another study showed, on the other hand, that in contrast to healthy controls, patients diag-nosed with schizophrenia demonstrated atypical facial mimicry,which was not associated with any clinical feature of the dis-order. The authors of this study suggested that this evidencemight account for a low-level disruption contributing to empa-thy deficits in schizophrenia (Varcin et al.,2010). Similarly,Wolf  et al. (2006)found an undecipherable and bizarre mimic pattern within a sample of patients suffering from schizophrenia, called“ mimic disintegration ” (seeHeimann and Spoerri,1957). Mimic disintegration is defined as the inability to organize specific facialmuscle movements as an integrated whole, thus making difficultfor observers to decode the emotional state and establish contactor develop a deeper relationship with the patients. Furthermore,many studies investigating everyday life of patients diagnosedwith schizophrenia documented an emotional-affective patterncharacterized by many negative and few positive experiences, thusmaking patients’ affectivity more negative. Some studies (Matteset al.,1995;Iwase et al.,1999;Wolf et al.,2004,2006) found a minor activity of  Zygomaticus muscle in response to positivestimuli, whereas another study (Sison et al.,1996) found an overall major activation of  Corrugator Supercilii muscle, inter-preted as a sign of the negative attitude showed by patients ineveryday life.Reduced emotional expression (i.e., flat affect) is not only atypical symptom of full-blown schizophrenia (Andreasen,1984a; Bleuler,1950). Many findings lend support to the assump- tion that vulnerability to schizophrenia may be subtly mani-fested in emotional behavior long before the onset of clinicalsymptoms. Furthermore, after schizophrenia onset, flat affectincreases (Walker et al.,1993). Reduced emotional facial expres- sion could be a disease risk index for high-vulnerability subjects(e.g., Schizotypal Personality patients and first degree relatives)(Phillips and Seidman,2008). Moreover, previous research on flat affect showed a disjunction between the expression and the expe-rience of emotion in schizophrenia (Bleuler,1950; Berenbaum and Oltmanns,1992;Kring et al.,1993;Kring and Neale,1996; Aghevli et al.,2003;Kring and Earnst,2003). These studies showed that patients with schizophrenia often reported experi-encing strong emotions, butthey were significantly less expressivethan controls. Thus, observers could note no visible sign of emotion.The studies using EMG recording to investigate emotionalexpression in schizophrenia, used different materials and meth-ods. In particular, often non-ecological stimuli, like static imagesnon-facial stimuli, or fiction movies were used. Many stud-ies indeed highlighted, on the other hand, the importance of dynamic stimuli in the evaluation of emotional expression. Arecent study on healthy individuals showed that presentation of dynamic facial expressions evokes stronger EMG responses thanstatic ones. Moreover, participants rated dynamic expressions asmore intense that static ones (Rymarczyk et al.,2011). Emotional facial expression communicates feelings, but is alsoan important low-level mechanism contributing to the expe-rience of empathy, thereby lying at the core of social interac-tion. Schizophrenia is associated with pervasive social cognitiveimpairments that include emotional processing of facial expres-sions. Despitesuchdisordermight playacrucialroleinempathiz-ing deficits and consequently impoverished social skills, previousresearch onfacialexpression ofemotions inschizophreniahasnot yielded unequivocal results. In particular, it remains unaddressedthe issue of patients’ facial expression as a medium of empathicresonance contributing to the recognition and evaluation of theperceived emotion expressed by others.The aim of this study was to investigate whether subjectivefacial mimicry affects the quantitative evaluation of the emo-tional content of perceived emotions presented through dynamicexpressive stimuli, in healthy participants and in patients diag-nosed with schizophrenia. To this purpose we employed a novelparadigm by means of which emotional dynamic ecological stim-uli were presented in the visual and auditory modalities in isola-tion and congruently or incongruently associated. This approachenabled us to study the dimensional quality and possible alter-ation of the emotional responses in these two experimentalgroups. MATERIALS ANDMETHODS PARTICIPANTS Thirty participants took part to the experiment. Control par-ticipants (CNT; ten males, five females, mean age 35.8 years SE  ± 2 . 3) were recruited by publicannouncement and were blindto the experimental goals. None of them reported the presence of any neurological or psychiatric disorder. Patient group (SZP; tenmales, five females, mean age 32.8 years SE  ± 1 . 7) were recruitedfrom the Clinical Psychiatry Institute of the University of Parma.Allofthemwerechronicclinicallystableoutpatients,mainlydiag-nosed with schizophrenia, paranoid subtype. Only one patientwas diagnosed with a disorganized subtype, one with an undif-ferentiated subtype and two patients with a residual subtype.Psychiatric diagnosis was established via a structured interview (Structured Clinical Interview for DSM–IV, SCID). Exclusioncriteria were the presence of neurological and vascular disor-ders, dysmetabolic syndrome, alcohol or drugs abuse and mentalretardation (Intelligence Quotient score < 70). All participantshad normal or corrected to normal vision. In addition to beingclosely matched for gender, the two groups did not differ in age[ t  ( 30 ) =− 1 . 06, p > 0 . 05]. All clinical participants (SZP) werereceiving antipsychotic medication (most of them were admin-istered new generation atypical antipsychotics). Since the age of onset and the illness duration indicated that the clinical sam-ple was heterogeneous, for comparing dosages of different drugswe converted doses of medication to chlorpromazine equivalents. Frontiers in Human Neurosciencewww.frontiersin.org July 2013 | Volume 7 | Article 368 | 2  Sestito et al. Facial EMG responses in patients with schizophrenia Then we multiplied these equivalents by the time an individualhad been on a given dose to obtain cumulative value measuredin dose-years. After each dose had been converted to dose-years,the results could be summed to provide a cumulative measure of lifetime exposure (Andreasen et al.,2010). In order to describe psychopathological features related withschizophrenia, patients were administered a variety of tests: scalefor the Assessment of Negative Symptoms (SANS;Andreasen,1984a), Scale for the Assessment of Positive Symptoms (SAPS;Andreasen,1984b),Social Anhedonia Scale(SAS;Chapmanet al., 1976), Physical Anhedonia Scale (PAS;Chapman et al.,1976). Given that all patients were under medication, we also adminis-tered them the Simpson-Angus Extrapyramidal side-effects Scale(Simpson and Angus,1970), an established, valid and reli- able instrument for assessing neuroleptic-induced parkinsonism(Janno et al.,2005). None of them were beyond cut-off value, indicating that SZP participants did not show any significantextrapyramidal side-effect related with drugs assumption. Detailsabout CNT and SZP samples are provided in Table 1 . Writteninformed consentwasobtained fromallparticipants beforeenter-ing the study. The local Ethical Committee approved the study. STIMULI Two professional actors (one male and one female) were usedfor stimuli preparation. Stimuli consisted of 2-s colored videoclips showing positive (laugh), negative (cry) and neutral (con-trol) emotions. The neutral video clips showed actors makingvarious faces (i.e., “making a face”) that did not imply any par-ticular emotional content, just that the actors were adoptingsome specific facial expressions. Actors when performed neutralstimuli always associated the making a face with specific vocaliza-tions. The sound of the neutral stimuli was a vocalization similarto “ahh,” “ohh,” or “eemmh.” Actors’ full face was presentedagainst a gray background. Stimuli consisted of actors’ Laugh(Positive), Cry (Negative) and Control (Neutral) accompaniedby the simultaneously produced sound of laughter, crying and anon-emotional sound, respectively. Half of the stimuli was per-formed by the male actor, whereas the other half was performedby the female actress. Stimuli were recorded using a digital cam-era(25frames/s,720 × 576pixels), withaudiodigitallyrecorded at44.1kHz. Stimuli were divided into four presentation modalities:Visual only, Audio only, Audio-Visual congruent and Audio-Visual incongruent. Every presentation modality was made of 60stimuli [24 Laugh (Positive) stimuli, 24 Cry (Negative) stimuliand 12 Control (Neutral) stimuli]. In the Audio modality (A),the sound of the video clips of laugh, cry and control stimuliwas extracted from the srcinal video clips and presented alone.In the Video modality (V), only the visual component of video-clips was presented, devoid of any sound. In the Audio-VisualCongruent modality (AVC), the srcinal video clips were pre-sented with both modalities. In the Incongruent Audio-Visualmodality (AVI), the video of a given expression was coupled andpresented with the audio pertaining to a different video clip per-formed by the same actor (e.g., audio of laugh with the videoof cry, audio of cry with the video of laughs and audio of agiven neutral sound with the video of another neutral stimulus).Consequently, in AVI Laugh participants saw an actor crying butheard laughing,in AVI Cry participants saw an actor laughing butheard crying, and in Control condition they saw an actor makinganunemotionalfacewhilehearingthesoundofadifferentneutralstimulus. EXPERIMENTAL PROCEDURE Participants were individually tested in a sound attenuated lab-oratory room. They were invited to sit on a comfortable chairin front of a 19-inch computer monitor used for stimuli pre-sentation, located at a distance of 70cm. Audio tracks werepresented at a comfortable sound level ( < 70dB) through loud-speakers integrated in the computer monitor. Before starting,participants were invited to relax and refrain from moving during Table 1 | Demographic variables and characteristics of Schizophrenia (SZP) and Control (CNT) participants.Characteristic Patients ControlsMean SE  Range Cut-off Mean SE  Range Age (years) 32 . 80 1 . 69 25–49 35 . 80 2 . 28 25–53SAPS 26 . 67 4 . 17 0–170SANS 48 . 09 4 . 56 0–125PAS 26 . 36 2 . 26 0–61 > 18SAS 19 . 00 1 . 74 0–40 > 12Simpson-Angus Scale 0 . 36 0 . 04 0–4 > 0 . 65Duration of illness (years) 11 . 23 1 . 30 2–24Age at first psychosis 22 . 69 0 . 66 19–28Number of hospitalizations 3 . 83 0 . 38 2–7Dose of typical and atypical antipsychotics 32 . 85 4 . 93Dose of atypical antipsychotics 24 . 84 4 . 00Dose of typical antipsychotics 8 . 01 1 . 48 Drugs are expressed as the cumulative value measured in dose-years in the form of (chlorpromazine equivalent in mg)  × (time on dose measured in years) ( Andreasen et al.,2010 ). Frontiers in Human Neurosciencewww.frontiersin.org July 2013 | Volume 7 | Article 368 | 3  Sestito et al. Facial EMG responses in patients with schizophrenia the experiment. Participants were instructed to carefully listen toand/or watch audiovisual stimuli. After exposure to each stimu-lus, participants were required to verbally rate how much positiveor negative the stimulus was perceived on a Likert scale rangingfrom − 3 (very negative) to + 3 (very positive), where 0 indicatedlack of perceived emotional content.The experiment consisted of four experimental blocks of 60stimuli each presented in randomized order. Each block consistedof one of the four modalities: Audio-Visual Congruent (AVC),Audio-Visual Incongruent (AVI), Audio (A) and Video (V). Inevery modality three emotional stimuli were presented in ran-domized sequence: Laugh (Positive), Cry (Negative) and Control(Neutral). A pause was provided at the end of each condition.The order of blocks was counterbalanced among participants.Each trial ( Figure1 ) started with a fixation cross (the “ + ” sym-bol) presented for 1000ms (baseline), immediately followed by the stimulus, which lasted 2000ms, then followed by a questionmark (the “?” symbol). After question mark presentation, partic-ipants verbally scored the emotional valence of each stimuli. Theexperimenter took note of participants’ response in a record sheetand then started manually the next trial. The total duration of theexperiment was about 40min. EMGRECORDING To measure facial muscle activity, Ag/AgCl surface electrodes(diameter 3mm) were attached bipolarly over the left (Dimbergand Petterson,2000) Zygomaticus major  and the Corrugator Supercilii muscleregions(Fridlund andCacioppo,1986).Inorder to reduce the inter-electrode impedance, the participants’ skinwas cleaned with alcohol and rubbed with the electrode paste.Continuous electromyography (EMG) recordings from bothmuscles were simultaneously acquired with a CED Micro 1401analog-to-digital converting unit (Cambridge Electronic Design,Cambridge, UK). The EMG signal was amplified (3000 × ), dig-itized (sampling rate: 2.5kHz) and stored on a computer foroffline analysis. DATA ANDSTATISTICAL ANALYSIS Behavioral rating  The rating score of each participant was averaged on the basis of modality and emotion. The corresponding averaged rating scoreswere entered into a 4 (Modality: AVC, AVI, A, V) × 3 (Emotion:Laugh, Cry, Control) × 2 (Group: SZP and CNT) repeated mea-sures ANOVA,with Modality and Emotion aswithin-participantsfactors and Group as between-participants factor. EMG data analysis  Offline, data were submitted to a 50–500Hz band-pass filter toreduce movement related artifacts and environmental noise, andfull-wave rectified. Data were then visually inspected, and datawith remaining artifacts were excluded from subsequent analy-sis [mean percentage of discarded trails: 14.1% for CNT, 12.6%for SZP; T  -test performed did not show significant differencesbetween groups t  ( 30 ) = 0 . 5, p > 0 . 6]. In accordance with ear-lier experiments (e.g.,Dimberg et al.,2000), any distinct muscle response to the stimuli was expected to be detectable after 500msof exposure. Thus, for each participant and trial, the averagedEMG responses of the two muscles were subdivided in 4 timeperiods (T1–T4) of 500ms each. Each time-bin was then nor-malized with respect to the baseline (i.e., averaged pre-stimulussignal activity lasting 500ms: from 250 to 750ms of the 1000mstotal duration of the baseline). Thus, an EMG normalized valueabove the 100% means an activation of a given muscle withrespect to the baseline, whereas an EMG normalized value below the 100% indicate a relaxation of that muscle with respect tothe baseline. In order to compare baselines, we performed twoANOVAs, one for each muscle, in which baselines raw data werecompared, with Modality (AVC, AVI,A, V) aswithin-participantsfactor and Group (SZP, CNT) as between-participants factor.Mean EMG responses were then calculated for each Modality (AVC, AVI,A,V),Emotion (Laugh,Cry, Control) andPeriod(T1,T2, T3, T4). EMG data were entered into a 4 (Modality: AVC,AVI, A, V) × 3 (Emotion: Laugh, Cry, Control) × 4 (Period: FIGURE 1 | Experimental paradigm. Photographs illustrate examples of stimuli depicting Laugh (A) , Cry (B) and Control (C) . Frontiers in Human Neurosciencewww.frontiersin.org July 2013 | Volume 7 | Article 368 | 4  Sestito et al. Facial EMG responses in patients with schizophrenia T1: 0–500ms, T2: 500–1000ms, T3: 1000–1500ms, T4: 1500–2000ms) repeated measures ANOVA, with Modality, Emotionand Periodasthe within-participants factors andGroup(SZPandCNT) as between-participants factor. One separated ANOVA wasconducted for each muscle (Corrugator and Zygomaticus). Functional relation between EMG and behavioral rating  In order to investigate functional relations between the recordedEMG responses and behavioral rating, we calculated medianEMG responses, separately for each group and for each emo-tion (positive, negative), irrespective of modalities and periods.We excluded from this analysis Control stimuli because they did not evoke any significant EMG response in both muscles(see Results). Regarding positive emotions, we considered forthis analysis the following modalities in which we measured (seeResults) Zygomaticus muscle activation: AVI Cry, AVC Laugh,A Laugh and V Laugh. Regarding negative emotions, we con-sidered the following modalities in which we measured (seeResults) Corrugator muscle activation: AVI Laugh, AVC Cry, ACry and V Cry.For each participant, we calculated the median EMG responsefor each emotion (positive, negative). If this value was equal orgreater than the median value calculated separately for positiveand negative emotions for the group the participant belongedto, we classified this participant as Externalizer. If, instead, thisvalue was smaller than the median value calculated separately for positive and negative emotions for the group the partici-pant belonged to, we classified this participant as Internalizer (seeKring and Gordon,1998). Following this procedure, in the CNT group we obtained the median value of 95.14% (8 Externalizersand 7 Internalizers) for positive emotions and the median valueof 99.24% (8 Externalizers and 7 Internalizers) for negative emo-tions. In the SZP group we obtained the median value of 95.15%(6 Externalizers and 9 Internalizers) for positive emotions andthe median value of 100% (6 Externalizers and 9 Internalizers)for negative emotions. The corresponding averaged rating scoreswere entered into a 4 (Modality: AVC, AVI, A, V) × 2 (Group:SZP and CNT) repeated-measures ANOVAs, with Modality aswithin-participants factor and Group as between-participantsfactor. Overall, we ran totally 4 ANOVAs, two in order to analyzebehavioral data of the Externalizer cohort (one for each emotionvalence: positive, negative) and two in orderto analyze behavioraldata of the Internalizer cohort (one for each emotion valence:positive, negative).For all performed analyses, the significance level was set at  p < 0 . 05. Post-hoc  comparisons (LSD Fisher test) were applied on allsignificant main factors and interactions. RESULTS BEHAVIORAL RESULTS Results of the repeated-measures ANOVA performed on behav-ioral rating scores showed that the factor Emotion was significant[ F  ( 2 , 56 ) = 222 . 52 p < 0 . 000]. Post-hoc  comparisons showed thatCry was rated by both groups more negative than Laugh andControl stimuli were considered without any emotional con-tent (all  p s < 0 . 000).Complementing this finding,the interactionbetween Emotion andModality[ F  ( 6 , 168 ) = 156 . 7  p < 0 . 000]wasalso significant( Figure 2 ). This interaction was due to the factthat the negative rating scores reported for Laugh stimuli duringthe AVI modality (in which participants saw cry and heard laugh)differed from the positive rating scores reported for Laugh stim-uli in all other modalities (all p s < 0 . 000). Similarly, the positiverating scores reported for Cry stimuli during the AVI modality (in which participants saw laugh and heard cry) significantly dif-fered from the negative rating scores reported for Cry stimuli inall other modalities (all p s < 0 . 000). These differences in ratingof AVI modality were due to the fact that both groups based theirratings on the emotion they saw (Laugh in AVI Cry and Cry inAVI Laugh), instead of the emotion they heard. Post-hoc  analysisalso showed that Control stimuli were rated as devoid of emo-tional content in all modalities by both groups (all p s < 0 . 000).Furthermore, with Laugh stimuli, V modality was rated morepositive than A modality (  p < 0 . 05).Results also showed a significant interaction Emotion by Group [ F  ( 2 , 56 ) = 3 . 43 p < 0 . 05]. However, post-hoc  analysesrevealed no significant differences between groups (all p s > 0 . 3). EMGRESULTS Two repeated measure ANOVAs, one for each muscle(Corrugator, Zygomaticus), were performed in order tocompare baselines between the two groups, with Modality (AVC,AVI, A, V) as within-participants factor and Group (SZP, CNT)as between-participants factor. We found no significant maineffect and interactions (all p s > 0 . 05). These results show that thebaselines were not significantly different between the two groups.Two repeated measures ANOVAs were performed in order toassess Zygomatic Major  and Corrugator Supercilii EMG responsesduring the presentation of the stimuli of positive, negative andneutral facial expressions and/or related sounds in four differentmodalities (AVC, AVI, A, V) (See Figures3 , 4 ). FIGURE 2 | Averaged rating scores detected for each modality (AVC,Audio-Visual Congruent; AVI, Audio-Visual Incongruent; A, Audio;V, Video) and emotion (Laugh, Cry, Control). Error bars representstandard errors of mean ( SE  ). Frontiers in Human Neurosciencewww.frontiersin.org July 2013 | Volume 7 | Article 368 | 5
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