Implicit Emotional Processing Task Research Articles

Neural correlates of emotional valence for faces and words.

Stimuli with negative emotional valence are especially apt to influence perception and action because of their crucial role in survival, a property that may not be precisely mirrored by positive emotional stimuli of equal intensity. The aim of this study was to identify the neural circuits differentially coding for positive and negative valence in the implicit processing of facial expressions and words, which are among the main ways human beings use to express emotions. Thirty-six healthy subjects took part in an event-related fMRI experiment. We used an implicit emotional processing task with the visual presentation of negative, positive, and neutral faces and words, as primary stimuli. Dynamic Causal Modeling (DCM) of the fMRI data was used to test effective brain connectivity within two different anatomo-functional models, for the processing of words and faces, respectively. In our models, the only areas showing a significant differential response to negative and positive valence across both face and word stimuli were early visual cortices, with faces eliciting stronger activations. For faces, DCM revealed that this effect was mediated by a facilitation of activity in the amygdala by positive faces and in the fusiform face area by negative faces; for words, the effect was mainly imputable to a facilitation of activity in the primary visual cortex by positive words. These findings support a role of early sensory cortices in discriminating the emotional valence of both faces and words, where the effect may be mediated chiefly by the subcortical/limbic visual route for faces, and rely more on the direct thalamic pathway to primary visual cortex for words.

Automatic and controlled attentional orienting toward emotional faces in patients with Parkinson’s disease

Parkinson’s disease (PD) is a neurodegenerative motor disorder that can associate with deficits in cognitive and emotional processing. In particular, PD has been reported to be mainly associated with defects in executive control and orienting attentional systems. The deficit in emotional processing mainly emerged in facial expression recognition. It is possible that the defects in emotional processing in PD may be secondary to other cognitive impairments, such as attentional deficits. This study was designed to systematically investigate the different weight of automatic and controlled attentional orienting mechanisms implied in emotional selective attention in PD. To address our purpose, we assessed drug-naïve PD patients and age-matched healthy controls with two dot-probe tasks that differed for stimuli duration. Automatic and controlled attentions were evaluated with stimuli lasting 100 ms and 500 ms, respectively. Furthermore, we introduced an emotion recognition task to investigate the performance in explicit emotion classification. The stimuli used in both the tasks dot-probe and emotion recognition were expressive faces displaying neutral, disgusted, fearful, and happy expressions.Our results showed that in PD patients, compared with healthy controls, there was 1) an alteration of automatic and controlled attentional orienting toward emotional faces in both the dot-probe tasks (with short and long durations), and 2) no difference in the emotion recognition task. These findings suggest that, from the early stages of the disease, PD can yield specific deficits in implicit emotion processing task (i.e., dot-probe task) despite a normal performance in explicit tasks that demand overt emotion recognition.

Enhanced salience of musical sounds in singers and instrumentalists.

Music training has been linked to facilitated processing of emotional sounds. However, most studies have focused on speech, and less is known about musicians' brain responses to other emotional sounds and in relation to instrument-specific experience. The current study combined behavioral and EEG methods to address two novel questions related to the perception of auditory emotional cues: whether and how long-term music training relates to a distinct emotional processing of nonverbal vocalizations and music; and whether distinct training profiles (vocal vs. instrumental) modulate brain responses to emotional sounds from early to late processing stages. Fifty-eight participants completed an EEG implicit emotional processing task, in which musical and vocal sounds differing in valence were presented as nontarget stimuli. After this task, participants explicitly evaluated the same sounds regarding the emotion being expressed, their valence, and arousal. Compared with nonmusicians, musicians displayed enhanced salience detection (P2), attention orienting (P3), and elaborative processing (Late Positive Potential) of musical (vs. vocal) sounds in event-related potential (ERP) data. The explicit evaluation of musical sounds also was distinct in musicians: accuracy in the emotional recognition of musical sounds was similar across valence types in musicians, who also judged musical sounds to be more pleasant and more arousing than nonmusicians. Specific profiles of music training (singers vs. instrumentalists) did not relate to differences in the processing of vocal vs. musical sounds. Together, these findings reveal that music has a privileged status in the auditory system of long-term musically trained listeners, irrespective of their instrument-specific experience.

Neurobehavioral correlates of impaired emotion recognition in pediatric PTSD.

Despite broad evidence suggesting that adversity-exposed youth experience an impaired ability to recognize emotion in others, the underlying biological mechanisms remains elusive. This study uses a multimethod approach to target the neurological substrates of this phenomenon in a well-phenotyped sample of youth meeting diagnostic criteria for posttraumatic stress disorder (PTSD). Twenty-one PTSD-afflicted youth and 23 typically developing (TD) controls completed clinical interview schedules, an emotion recognition task with eye-tracking, and an implicit emotion processing task during functional magnetic resonance imaging )fMRI). PTSD was associated with decreased accuracy in identification of angry, disgust, and neutral faces as compared to TD youth. Of note, these impairments occurred despite the normal deployment of visual attention in youth with PTSD relative to TD youth. Correlation with a related fMRI task revealed a group by accuracy interaction for amygdala-hippocampus functional connectivity (FC) for angry expressions, where TD youth showed a positive relationship between anger accuracy and amygdala-hippocampus FC; this relationship was reversed in youth with PTSD. These findings are a novel characterization of impaired threat recognition within a well-phenotyped population of severe pediatric PTSD. Further, the differential amygdala-hippocampus FC identified in youth with PTSD may imply aberrant efficiency of emotional contextualization circuits.

Neural correlates of emotion processing predict resilience in youth at familial risk for mood disorders.

Aberrant face emotion processing has been demonstrated in youth with and at a familial risk for bipolar and major depressive disorders. However, the neurobiological factors related to emotion processing that underlie resilience from youth-onset mood disorders are not well understood. Functional magnetic resonance imaging data during an implicit emotion processing task were collected at baseline from a sample of 50 youth, ages 8-17, who were healthy but also familially at high risk for either bipolar disorder or major depressive disorder, and 24 healthy controls with no family history of psychopathology (HCL). Participants were reevaluated 3 years later and classified into three groups for analysis: high-risk youth who converted to a psychiatric diagnosis (CVT; N = 23), high-risk youth who were resilient from developing any psychopathology (RES; N = 27), and HCL youth (N = 24) who remained healthy at follow-up. For happy > calm faces, the CVT and RES groups had significantly lower activation in the left inferior parietal lobe (IPL), while the RES group had lower activation in the right supramarginal gyrus. For fear > calm faces, the RES group had lower activation in the right precuneus and inferior frontal gyrus (IFG) compared to the CVT group. Connectivity analyses revealed the RES group exhibited higher left IPL connectivity with visual cortical regions for happy > calm faces, and higher IFG connectivity with frontal, temporal, and limbic regions for fear > calm faces. These connectivities were correlated with improvements in prosocial behaviors and global functioning. Our findings suggest that differential activation and connectivity in the IPL, IFG, and precuneus in response to emotional stimuli may represent distinct resilience and risk markers for youth-onset mood disorders.

Interaction between hypothalamic-pituitary-adrenal axis genetic variation and maternal behavior in the prediction of amygdala connectivity in children

High levels of negative, and low levels of positive parenting behaviors can increase the risk of internalizing symptoms in children, but the mechanisms underlying this association are still unclear. One possibility is that parenting behaviors affect the neural correlates of emotion processing in children. Further, genetic variants relevant to the function of the hypothalamic–pituitary–adrenal (HPA) axis are thought to moderate the effect of early experiences on the brain circuits underlying emotion processing, particularly those involving the amygdala. However, no studies have investigated the interactive effect of parenting behaviors and HPA axis-related genes on amygdala activity and connectivity during emotion processing, and in turn internalizing symptoms in children. Participants comprised 80 children (46 females, mean age = 10.0 years) from the community. Observational measures of maternal behavior were collected during mother-child interactions. Children underwent functional magnetic resonance imaging while performing an implicit emotion-processing task, and mothers and children completed measures of child internalizing symptoms. Genetic risk was calculated using an HPA genetic risk score. HPA genetic risk score was indirectly associated with greater child self-reported depressive symptoms via increased amygdala-precuneus connectivity during the emotion-processing task, and interacted with negative maternal parenting behavior to predict increased connectivity between amygdala and superior frontal gyrus, anterior cingulate cortex and parietal cortex. HPA-related genetic variation appears to moderate the effect of negative maternal parenting behavior on the neural underpinnings of emotion processing in children, and may confer risk for depressive symptoms via modulation of amygdala connectivity.

The Influence of Maternal Parenting Style on the Neural Correlates of Emotion Processing in Children

The importance of parenting in influencing mental health outcomes, particularly depression, during childhood and adolescence is well known. However, the mechanisms are unclear. Emotion processing impairments in children are believed to be influenced by negative parenting behaviors and fundamental to depression. As such, investigating the association between parenting behavior and the neural underpinnings of emotion processing in children could provide fundamental clues as to the link between parenting and depression. Eighty-six children (49 girls, mean age 10.1 years), as part of a longitudinal study, participated. Observational measures of maternal behavior were collected during 2 mother-child interactions. Children underwent functional magnetic resonance imaging while performing an implicit emotion-processing task, and measures of child internalizing symptoms were collected. Maternal negative behavior exhibited during an event-planning interaction was associated with decreased activation in the lingual gyrus in girls, whereas maternal negative behavior during a problem-solving interaction was associated with increased amygdala activation in the entire sample during processing of angry and fearful faces. Maternal communicative behavior during the 2 mother-child interactions was associated with increased activity in the bilateral middle orbitofrontal cortex in the entire sample. Negative behavior during the problem-solving interaction was associated with connectivity between the amygdala and superior parietal lobe. Brain activity/connectivity was not related to internalizing symptoms. Results suggest that, in children, maternal behavior could be associated with activity in brain regions involved in emotion processing. However, more research is needed to elucidate the link among parenting, emotion processing, and depressive symptoms in young people.

Influence of Familial Risk for Depression on Cortico-Limbic Connectivity During Implicit Emotional Processing.

Imbalances in cortico-limbic activity and functional connectivity (FC) supposedly underlie biased emotional processing and present putative intermediate phenotypes (IPs) for major depressive disorder (MDD). To prove the validity of these IPs, we assessed them in familial risk. In 70 healthy first-degree relatives of MDD patients and 70 controls, brain activity and seed-based amygdala FC were assessed during an implicit emotional processing task for fMRI containing angry and fearful faces. Using the generalized psychophysiological interaction approach, amygdala FC was assessed (a) across conditions to provide comparable data to previous studies and (b) compared between conditions to elucidate its implications for emotional processing. Associations of amygdala FC with self-reported negative affect were explored post hoc. Groups did not differ in brain activation. In relatives, amygdala FC across conditions was decreased with superior and medial frontal gyrus (SFG, MFG) and increased with subgenual and perigenual anterior cingulate cortex (sgACC, pgACC). NA was inversely correlated with amygdala FC with MFG, pgACC and their interaction in relatives. Relatives showed aberrant condition-dependent modulations of amygdala FC with visual cortex, thalamus and orbitofrontal cortex. Our results do not support imbalanced cortico-limbic activity as IP for MDD. Diminished amygdala-dorsomedial prefrontal FC in relatives might indicate insufficient regulatory capacity, which appears to be compensated by ventromedial prefrontal regions. Differential task-dependent modulations of amygdala FC are discussed as a stronger involvement of automatic instead of voluntary emotional processing pathways. Reliability and etiological implications of these results should be investigated in future studies including longitudinal designs and patient-risk-control comparisons.

Interaction between DRD2 variation and sound environment on mood and emotion-related brain activity

Sounds, like music and noise, are capable of reliably affecting individuals’ mood and emotions. However, these effects are highly variable across individuals. A putative source of variability is genetic background. Here we explored the interaction between a functional polymorphism of the dopamine D2 receptor gene (DRD2 rs1076560, G>T, previously associated with the relative expression of D2S/L isoforms) and sound environment on mood and emotion-related brain activity. Thirty-eight healthy subjects were genotyped for DRD2 rs1076560 (G/G=26; G/T=12) and underwent functional magnetic resonance imaging (fMRI) during performance of an implicit emotion-processing task while listening to music or noise. Individual variation in mood induction was assessed before and after the task. Results showed mood improvement after music exposure in DRD2GG subjects and mood deterioration after noise exposure in GT subjects. Moreover, the music, as opposed to noise environment, decreased the striatal activity of GT subjects as well as the prefrontal activity of GG subjects while processing emotional faces. These findings suggest that genetic variability of dopamine receptors affects sound environment modulations of mood and emotion processing.

Amygdala-prefrontal cortical functional connectivity during implicit emotion processing differentiates youth with bipolar spectrum from youth with externalizing disorders

ObjectiveBoth bipolar spectrum disorders (BPSD) and attention deficit hyperactivity disorder (ADHD) present with emotion-regulation deficits, but require different clinical management. We examined how the neurobiological underpinnings of emotion regulation might differentiate youth with BPSD versus ADHD (and healthy controls, HCs), specifically assessing functional connectivity (FxC) of amygdala-prefrontal circuitry during an implicit emotion processing task. MethodsWe scanned a subset of the Longitudinal Assessment of Manic Symptoms (LAMS) sample, a clinically recruited cohort with elevated behavioral and emotional dysregulation, and age/sex-ratio matched HCs. Our sample consisted of 22 youth with BPSD, 30 youth with ADHD/no BPSD, and 26 HCs. We used generalized psychophysiological interaction (gPPI) to calculate group differences to emerging emotional faces vs. morphing shapes in FxC between bilateral amygdala and ventral prefrontal cortex/anterior cingulate cortex. ResultsFxC between amygdala and left ventrolateral prefrontal cortex (VLPFC) in response to emotions vs. shapes differed by group (p=.05): while BPSD showed positive FxC (emotions>shapes), HC and ADHD showed inverse FxC (emotions<shapes). A group x emotion interaction was found in amygdala-subgenual cingulate FxC (p=.025), explained by differences in FxC in response to negative emotions. While BPSD showed positive FxC, HC showed inverse FxC; ADHD were intermediate. Amygdala-subgenual FxC was also positively associated with depressive symptoms and stimulant medication. LimitationsCo-morbidity and relatively small sample size. ConclusionsYouth with BPSD showed abnormally positive FxC between amygdala and regions in the ventral prefrontal cortex during emotion processing. In particular, the amygdala-VLPFC finding was specific to BPSD, and not influenced by other diagnoses or medications.

Within- and Between-Session Changes in Neural Activity During Emotion Processing in Unipolar and Bipolar Depression

BackgroundBipolar disorder (BD) and unipolar depression (UD) can be difficult to distinguish clinically, particularly during episodes of depression. In this study, we test for differences between adults with BD, adults with UD, and healthy control (HC) adults regarding within-session and between-session changes in blood oxygen level–dependent (BOLD) response during implicit emotional processing. MethodsDuring functional magnetic resonance imaging, HC adults (n = 19) and adults with UD (n = 19) and BD (n = 16) performed an implicit emotion processing task. Each participant was scanned twice, separated by 6 months, resulting in 108 scans. The BOLD response and linear change in BOLD response were examined within and between sessions. ResultsWe observed within-session linear decreases in BOLD signal (regardless of group, condition, or session) in the left amygdala, a right-sided temporoparietal region, and a right-sided frontoinsular region. We also observed group differences in within-session BOLD signal change (p < .05, familywise error corrected) in a left-sided striatoinsular-thalamic region. Adults with BD demonstrated a linear decrease in BOLD signal compared with HC adults (p < .008, familywise error corrected) across this region and compared with adults with UD in the posterior insula portion of the region (p < .008, familywise error corrected). Finally, we observed main effects of emotional valence in bilateral visuospatial processing regions as well as in the left and right amygdala. ConclusionsAdults with BD demonstrated linear attenuation of BOLD response to emotional stimuli within left-sided striatoinsular-thalamic regions. Adults with BD may either have experienced abnormal habituation in this region or have disengaged quickly from processing the emotional stimuli, despite comparable task performance. This pattern may represent an underlying pathophysiologic process associated with BD that differs from UD.

Default mode network alterations during implicit emotional faces processing in first-episode, treatment-naive major depression patients.

Previous studies have focused on resting-state default mode network (DMN) alterations in the development and maintenance of depression; however, only a few studies have addressed DMN changes during task-related processing and their results are inconsistent. Therefore, we explored DMN patterns in young adult patients with first-episode, treatment-naïve major depressive disorder (MDD) performing an implicit emotional processing task. Patients with MDD (N = 29) and healthy controls (N = 33) were subjected to functional magnetic resonance imaging (fMRI) at rest and while performing a gender judgment task. Group independent component analysis (ICA) was used to identify DMN component under task state for both groups. The DMN of participants with MDD had decreased functional connectivity in bilateral prefrontal areas compared to controls. Right prefrontal gyrus connectivity for MDD patients correlated negatively with scores on maladaptive scales of the Cognitive Emotion Regulation Questionnaire (CERQ). Our findings suggest that depressed people have altered DMN patterns during implicit emotional processing, which might be related to impaired internal monitoring and emotional regulation ability.

Self perception and facial emotion perception of others in anorexia nervosa

Background: Whether individuals with anorexia nervosa (AN) are able to accurately perceive emotions from faces of others is unclear. Furthermore, whether individuals with AN process images of their own face differently to healthy individuals has thus far not been investigated. Therefore, the aim of this study was to investigate facial affect processing and the processing of one’s own face through measures of emotion identification, functional magnetic resonance imaging (fMRI) and eyetracking.Methods: Twenty-four females with AN and 25 matched healthy control participants were presented with an implicit emotion processing task during fMRI and eyetracking, followed by an explicit emotion identification task.Results: The AN group were found to ‘hyperscan’ stimuli and avoided visually attending to salient features of their own face images. Results of the fMRI revealed increased activity to own face stimuli in AN in the right inferior and middle temporal gyri, and right lingual gyrus. AN participants were not found to display emotion identification deficits to the standard emotional face stimuli.Discussion: The findings are discussed in terms of increased anxiety to disorder-relevant stimuli in AN. Potential clinical implications are discussed in relation to the use of eyetracking techniques to improve the perception of self in AN.

Implicit processing of visual emotions is affected by sound-induced affective states and individual affective traits.

The ability to recognize emotions contained in facial expressions are affected by both affective traits and states and varies widely between individuals. While affective traits are stable in time, affective states can be regulated more rapidly by environmental stimuli, such as music, that indirectly modulate the brain state. Here, we tested whether a relaxing or irritating sound environment affects implicit processing of facial expressions. Moreover, we investigated whether and how individual traits of anxiety and emotional control interact with this process. 32 healthy subjects performed an implicit emotion processing task (presented to subjects as a gender discrimination task) while the sound environment was defined either by a) a therapeutic music sequence (MusiCure), b) a noise sequence or c) silence. Individual changes in mood were sampled before and after the task by a computerized questionnaire. Additionally, emotional control and trait anxiety were assessed in a separate session by paper and pencil questionnaires. Results showed a better mood after the MusiCure condition compared with the other experimental conditions and faster responses to happy faces during MusiCure compared with angry faces during Noise. Moreover, individuals with higher trait anxiety were faster in performing the implicit emotion processing task during MusiCure compared with Silence. These findings suggest that sound-induced affective states are associated with differential responses to angry and happy emotional faces at an implicit stage of processing, and that a relaxing sound environment facilitates the implicit emotional processing in anxious individuals.

Reduced beta connectivity during emotional face processing in adolescents with autism.

BackgroundAutism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by impairments in social cognition. The biological basis of deficits in social cognition in ASD, and their difficulty in processing emotional face information in particular, remains unclear. Atypical communication within and between brain regions has been reported in ASD. Interregional phase-locking is a neurophysiological mechanism mediating communication among brain areas and is understood to support cognitive functions. In the present study we investigated interregional magnetoencephalographic phase synchronization during the perception of emotional faces in adolescents with ASD.MethodsA total of 22 adolescents with ASD (18 males, mean age =14.2 ± 1.15 years, 22 right-handed) with mild to no cognitive delay and 17 healthy controls (14 males, mean age =14.4 ± 0.33 years, 16 right-handed) performed an implicit emotional processing task requiring perception of happy, angry and neutral faces while we recorded neuromagnetic signals. The faces were presented rapidly (80 ms duration) to the left or right of a central fixation cross and participants responded to a scrambled pattern that was presented concurrently on the opposite side of the fixation point. Task-dependent interregional phase-locking was calculated among source-resolved brain regions.ResultsTask-dependent increases in interregional beta synchronization were observed. Beta-band interregional phase-locking in adolescents with ASD was reduced, relative to controls, during the perception of angry faces in a distributed network involving the right fusiform gyrus and insula. No significant group differences were found for happy or neutral faces, or other analyzed frequency ranges. Significant reductions in task-dependent beta connectivity strength, clustering and eigenvector centrality (all P <0.001) in the right insula were found in adolescents with ASD, relative to controls.ConclusionsReduced beta synchronization may reflect inadequate recruitment of task-relevant networks during emotional face processing in ASD. The right insula, specifically, was a hub of reduced functional connectivity and may play a prominent role in the inability to effectively extract emotional information from faces. These findings suggest that functional disconnection in brain networks mediating emotional processes may contribute to deficits in social cognition in this population.Electronic supplementary materialThe online version of this article (doi:10.1186/2040-2392-5-51) contains supplementary material, which is available to authorized users.

Which feature is fixated modulates the N170 regardless of facial expression

Facial expressions represent an important part of non-verbal communication used in everyday life. The N170 is widely regarded as a face-sensitive potential and has been linked to facial structural encoding, however it remains debated whether the N170 is modulated by facial expressions of emotion. We investigated how attention to facial features affects the early stages of emotion perception during an implicit emotion processing task. ERPs were recorded in response to presentations of fearful, joyful, or neutral facial expressions while fixation was restricted to the left eye, right eye, nose, or mouth using an eye tracker. Participants’ task was to discriminate the face gender. Enhanced N170 amplitudes and longer latencies were found when participants were fixated on the left and right eyes compared to the mouth and nose irrespective of emotion. Importantly, the N170 was not modulated by emotion. The results support the view that the N170 component is not sensitive to the facial expression in an implicit emotional task. In contrast, which feature is fixated modulates this component. As the eyes have been shown to be the diagnostic feature used to correctly categorize face gender, it could be that attention to the diagnostic feature is what drives N170 modulation with emotion in previous studies not controlling for fixation. This idea is currently being tested using an explicit emotional task with the same stimuli. Meeting abstract presented at VSS 2013

Prefrontal cortical response to emotional faces in individuals with major depressive disorder in remission

Abnormalities in the response of the orbitofrontal cortex (OFC) and dorsolateral prefrontal cortex (DLPFC) to negative emotional stimuli have been reported in acutely depressed patients. However, there is a paucity of studies conducted in unmedicated individuals with major depressive disorder in remission (rMDD) to assess whether these are trait abnormalities. To address this issue, 19 medication-free rMDD individuals and 20 healthy comparison (HC) participants were scanned using functional magnetic resonance imaging while performing an implicit emotion processing task in which they labeled the gender of faces depicting negative (fearful), positive (happy) and neutral facial expressions. The rMDD and HC groups were compared using a region-of-interest approach for two contrasts: fear vs. neutral and happy vs. neutral. Relative to HC, rMDD showed reduced activation in left OFC and DLPFC to fearful (vs. neutral) faces. Right DLPFC activation to fearful (vs. neutral) faces in the rMDD group showed a significant positive correlation with duration of euthymia. The findings support deficits in left OFC and DLPFC responses to negative emotional stimuli during euthymic periods of MDD, which may reflect trait markers of the illness or a ‘scar’ due to previous depression. Recovery may also be associated with compensatory increases in right DLPFC functioning.

Comparative processing of emotional prosody and semantics following basal ganglia infarcts: ERP evidence of selective impairments for disgust and fear

There is evidence from neuroimaging and clinical studies that functionally link the basal ganglia to emotional speech processes. However, in most previous studies, explicit tasks were administered. Thus, the underlying mechanisms substantiating emotional speech are not separated from possibly process-related task effects. Therefore, the current study tested emotional speech processing in an event-related potential (ERP) experiment using an implicit emotional processing task (probe verification). The interactive time course of emotional prosody in the context of emotional semantics was investigated using a cross-splicing method. As previously demonstrated, combined prosodic and semantic expectancy violations elicit N400-like negativities irrespective of emotional categories in healthy listeners. In contrast, basal ganglia patients show this negativity only for the emotions of happiness and anger, but not for fear or disgust. The current data serve as first evidence that lesions within the left basal ganglia affect the comparative online processing of fear and disgust prosody and semantics. Furthermore, the data imply that previously reported emotional speech recognition deficits in basal ganglia patients may be due to misaligned processing of emotional prosody and semantics.

Early emotional prosody perception based on different speaker voices

Decoding verbal and nonverbal emotional expressions is an important part of speech communication. Although various studies have tried to specify the brain regions that underlie different emotions conveyed in speech, few studies have aimed to specify the time course of emotional speech decoding. We used event-related potentials to determine when emotional speech is first differentiated from neutral speech. Participants engaged in an implicit emotional processing task (probe verification) while listening to emotional sentences spoken by a female and a male speaker. Independent of speaker voice, emotional sentences could be differentiated from neutral sentences as early as 200 ms after sentence onset (P200), suggesting rapid emotional decoding.

Modulation of neural response to happy and sad faces by acute tryptophan depletion

Central serotonin (5HT) plays a major role in emotional processing. We used functional neuroimaging (fMRI) to investigate the effects of experimental manipulation of central 5HT levels on the regional neural response to happy and sad facial expressions. Ten healthy participants (eight men and two women) were scanned during an implicit emotional processing task after receiving a tryptophan-free (acute tryptophan depletion, ATD) or a balanced amino acid drink in a double-blind design. ATD lowered total plasma tryptophan concentration by 80%. There was no significant effect on subjective mood ratings, on response accuracy and on reaction times. Compared to sham depletion, ATD attenuated activation in the right medial/inferior frontal gyrus, the posterior cingulate cortex, the occipital and parietal cortex bilaterally, the right hippocampus, claustrum and insula. Conversely, ATD was associated with relatively increased activation in the left inferior frontal gyrus. ATD had differential effects on activation during the processing of happy and sad faces in the right putamen and in the left superior temporal gyrus. In both cortical and sub-cortical regions, the neural response associated with processing emotional faces is significantly modulated by 5HT manipulation resulting from ATD. Moreover, in certain areas, this effect of 5HT depends on the emotional valence of the stimulus.