Emotion in voice matters: Neural correlates of emotional prosody perception

The ability to perceive emotions is imperative for successful interpersonal functioning. The present study examined the neural characteristics of emotional prosody perception with an exploratory event-related potential analysis. Participants were 59 healthy individuals who completed a discrimination task presenting 120 semantically neutral word pairs from five prosody conditions (happy/happy, angry/angry, neutral/neutral, angry/happy, happy/angry). The task required participants to determine whether words in the pair were spoken in same or different emotional prosody. Reflective of an initial processing stage, the word 1 N1 component was found to have greatest amplitude in parietal regions of the hemispheres, and was largest for emotional compared to neutral stimuli, indicating detection of emotion features. A second processing stage, represented by word 1 P2, showed similar topographic effects; however, amplitude was largest for happy in the left hemisphere while angry was largest in the right, illustrating differentiation of emotions. At the third processing stage, word 1 N3 amplitude was largest in frontal regions, indicating later cognitive processing occurs in the frontal cortex. N3 was largest for happy, which had lowest accuracy compared to angry and neutral. The present results support Schirmer and Kotz's (2006) model of vocal emotion perception because they elucidated the function and ERP components by reflecting three primary stages of emotional prosody perception, controlling for semantic influence.     

A right‐ear bias of auditory selective attention is evident in alpha oscillations

Auditory selective attention makes it possible to pick out one speech stream that is embedded in a multispeaker environment. We adapted a cued dichotic listening task to examine suppression of a speech stream lateralized to the nonattended ear, and to evaluate the effects of attention on the right ear's well‐known advantage in the perception of linguistic stimuli. After being cued to attend to input from either their left or right ear, participants heard two different four‐word streams presented simultaneously to the separate ears. Following each dichotic presentation, participants judged whether a spoken probe word had been in the attended ear's stream. We used EEG signals to track participants' spatial lateralization of auditory attention, which is marked by interhemispheric differences in EEG alpha (8–14 Hz) power. A right‐ear advantage (REA) was evident in faster response times and greater sensitivity in distinguishing attended from unattended words. Consistent with the REA, we found strongest parietal and right frontotemporal alpha modulation during the attend‐right condition. These findings provide evidence for a link between selective attention and the REA during directed dichotic listening.     

Selective attention to threatening faces in delusion‐prone individuals

Introduction. Selective attention to threat‐related information has been associated with clinical delusions in schizophrenia and nonclinical delusional ideation in healthy individuals. However, it is unclear whether biased attention for threat reflects early engagement effects on selective attention, or later difficulties in disengaging attention from perceived threat. The present study examined which of these processes operate in nonclinical delusion‐prone individuals.

Methods. A total of 100 psychologically healthy participants completed the Peters et al. () Delusions Inventory (PDI). Twenty‐two scoring in the upper quartile (high‐PDI group) and 22 scoring in the lower quartile (low‐PDI group) completed a modified dot‐probe task. Participants detected dot‐probes appearing 200, 500, or 1250 ms after an angry‐neutral face pair or a happy‐neutral face pair.

Results. High‐PDI individuals responded faster to dot‐probes presented in the same location as angry compared to happy faces at the short 200 ms stimulus onset asynchrony (SOA), but only when the emotional faces were presented to the left visual field. At the two longer SOAs (500 ms, 1250 ms), the high‐PDI group were also faster to respond to dot‐probes presented in the same location as angry compared to happy faces and slower to respond to dot‐probes presented in different spatial locations to angry (vs. happy) faces. The latter effects were seen whether emotional faces were presented to the left or the right visual field.

Conclusions. Results support the operation of emotion‐selective engagement and defective disengagement for threat‐related facial expressions (i.e., anger) in delusion‐prone individuals.     

Current status of the anger superiority hypothesis: A meta‐analytic review of N2pc studies

Numerous investigators have tested contentions that angry faces capture early attention more completely than happy faces do in the context of other faces. However, syntheses of studies on early event‐related potentials related to the anger superiority hypothesis have yet to be conducted, particularly in relation to the N200 posterior‐contralateral (N2pc) component which provides a reliable electrophysiological index related to orienting of attention suitable for testing this hypothesis. Fifteen samples (N = 534) from 13 studies featuring the assessment of N2pc amplitudes during exposure to angry‐neutral and/or happy‐neutral facial expression arrays were included for meta‐analysis. Moderating effects of study design features and sample characteristics on effect size variability were also assessed. N2pc amplitudes elicited by affectively valenced expressions (angry and happy) were significantly more pronounced than those elicited by neutral expressions. However, the mean effect size difference between angry and happy expressions was ns. N2pc effect sizes were moderated by sample age, number of trials, and nature of facial images used (schematic vs. real) with larger effect sizes observed when samples were comparatively younger, more task trials were presented and schematic face arrays were used. N2pc results did not support anger superiority hypothesis. Instead, attentional resources allocated to angry versus happy facial expressions were similar in early stages of processing. As such, possible adaptive advantages of biases in orienting toward both anger and happy expressions warrant consideration in revisions of related theory.     

Perceptual aberration and brain hemisphere reversal of foreperiod effect on time estimation

An auditory warning signal of 3 seconds' duration was followed by tachistoscopic presentation of a single dark dot to either the left or the right visual field (N = 18). The warning signal was presented monaurally to the left or to the right ear. The duration of the warning signal constituted foreperiod. The task was verbal estimation of the duration of the dot. For those who showed little or no sign of aberration of personal body image, as detected by Chapman's Perceptual Aberration Scale, time estimation of dot duration tended to be longer when the warning signal was presented to the left ear than to the right ear. For those who showed substantial sign of such aberration, the laterality of foreperiod effect was reversed, so that time estimation of dot duration was longer for the right ear than for the left ear. There was no such hemispheric reversal in terms of visual field.     

Reliability and magnitude of perceptual asymmetries in a dichotic word recognition task

The hypothesis that control of idiosyncratic attention deployment and retrieval strategies would improve the reliability and magnitude of laterality effects obtained in an auditory word recognition task was investigated. Sixty participants completed a dichotic word recognition task under 1 of 3 conditions. In free recall, they reported the 2 words presented on each trial (1 to each ear). In focused attention, they reported only the word presented to a prespecified ear. In target detection, they indicated whether a target word was presented to either ear on each trial. Results showed that the target-detection condition produced the largest and most reliable laterality effects compared with the other 2 conditions. The mechanisms likely to be responsible for these findings are discussed.     

When anger dominates the mind: Increased motor corticospinal excitability in the face of threat

Threat demands fast and adaptive reactions that are manifested at the physiological, behavioral, and phenomenological level and are responsive to the direction of threat and its severity for the individual. Here, we investigated the effects of threat directed toward or away from the observer on motor corticospinal excitability and explicit recognition. Sixteen healthy right‐handed volunteers completed a transcranial magnetic stimulation (TMS) task and a separate three‐alternative forced‐choice emotion recognition task. Single‐pulse TMS to the left primary motor cortex was applied to measure motor evoked potentials from the right abductor pollicis brevis in response to dynamic angry, fearful, and neutral bodily expressions with blurred faces directed toward or away from the observer. Results showed that motor corticospinal excitability increased independent of direction of anger compared with fear and neutral. In contrast, anger was better recognized when directed toward the observer compared with when directed away from the observer, while the opposite pattern was found for fear. The present results provide evidence for the differential effects of threat direction on explicit recognition and motor corticospinal excitability. In the face of threat, motor corticospinal excitability increases independently of the direction of anger, indicative of the importance of more automatic reactions to threat.     

Left hemisphere advantage for classical conditioning to auditory verbal CSs: Effects of nonattended extinction

The effects of brain laterality, or hemispheric asymmetry, on electrodermal classical conditioning during both attended and nonattended stimulus conditions were studied. Participants were conditioned to consonant-vowel (CV) syllables during an acquisition, or learning, phase of the experiment. During a subsequent extinction phase, the conditioned stimuli (CS) were presented in a dichotic mode of presentation. Half of the participants attended to the left car (right hemisphere) during the extinction phase and the other half of the participants attended to the right ear (left hemisphere). The results showed effects of conditioning for all participants during the acquisition phase. During dichotic extinction, the left hemisphere group showed remaining learning effects in both the attended and nonattended conditions, whereas the right hemisphere group demonstrated conditioning only in the attended condition.     

Instability of hemispheric asymmetry in dyslexic children.

The study tested the hypothesis of abnormal brain asymmetry in dyslexic children. Two dyslexic groups classified as "phonetic disorder" and "language disorder" and a control group participated in two experiments. In both experiments was employed a dichotic listening procedure consisting in recalling pairs of words presented simultaneously to two ears. In Experiment I the children were to recognize four words presented at a level of loudness typical for natural speech. In Experiment II only two words were used in each trial but they were presented at a low intensity level. The recognition scores for stimuli presented to the left and right ears were compared. In Experiment I all groups of children showed a typical right ear/left hemisphere superiority, i.e. their recognition scores were higher for the right than for the left ear. Dyslexics, however, performed significantly less well. In Experiment II the control children and those from "phonetic disorder" group again performed better when words were presented to their right ears. Unlike those two groups, the children from "language disorder group" showed the right hemisphere superiority, i.e. they performed better in the left ear presentation condition. The results do not support the hypothesis that dyslexic children have abnormal lateralization of verbal functions. They suggest that the pattern of hemispheric asymmetry in dyslexics is less stable and depends both on the kind of dyslexia and on task variation.     

Laterality, word valence, and visual attention: a comparison of depressed and non-depressed individuals.

Thirteen depressed and 13 non-depressed college students attended to valence-loaded word pairs (euphoric/dysphoric, euphoric/neutral, and neutral/dysphoric) on a computer screen. Each pair was observed through a viewing box with a vertical partition, each word in a different visual field. As a prior-entry task (Titchener, 1908) the words were simultaneously replaced by colored bars. Participants indicated which color bar (left or right) was seen first. As predicted, identifications of color bars following euphoric words in the right visual field (left hemisphere) exceeded their identification in the left visual field (right hemisphere). Also, as predicted, the non-depressed participants made identifications following the euphoric word of a pair more often than did the depressed participants. No interaction occurred between laterality and participant classification. Implications for research and therapy are discussed.     

On the perception of sarcasm in dichotic listening

The purpose of the present study was to investigate the processing of sincere and sarcastic statements by the cerebral hemispheres. Forty right-handed students were asked to localize sincere and sarcastic statements presented dichotically. Participants either indicated the ear that perceived the sarcastic statement or the ear that perceived the sincere statement in counterbalanced blocks of trials. As expected, results revealed a left ear advantage for sarcastic statements and a right ear advantage for sincere statements. In addition, participants showed faster response time when localizing targets (both sarcastic and sincere) to the left ear compared to the right. Finally, a significant negative correlation between laterality effects in the two tasks provided support for causal hemispheric complementarity. Results are discussed with reference to the contribution of the right and left hemispheres to language processing. Their implications for models of sarcasm perception are also discussed.     

Neurolinguistic deficits and the left hemisphere in the reading disabled

The relationship between cerebral laterality and neuropsychological functions, particularly phonemic analysis, was examined in a group of 20 reading disabled (RD) and 20 nonreading disabled (NRD) 8‐ to 12‐year‐old boys. Compared with NRD children, RD children exhibited an equivalent right ear and left hemispheric superiority for reporting dichotically presented words. However, even with experimental control for attention, the RD boys’ performance was poorer than NRD boys with both left and right ears. In addition, the RD children displayed poor performance on nine scales of the Luria Nebraska Neuropsychological Battery‐Children's Revision (LNNB‐CR), and had the most difficulty with the scales and items designed to tap left hemispheric dysfunction (i.e., the Left Sensorimotor, Receptive Speech, Expressive Language, Reading, and Writing scales). All of the RD children also performed poorer than any NRD child on a test of phonemic analysis, the Lindamood Test of Auditory Conceptualization (LAC), which assesses phonemic functions presumably best processed by the left hemisphere. In contrast, the RD children performed equivalently to NRD children on tasks considered best performed by the right hemisphere, including dichotically presented melodies and the Visual and Right Sensorimotor scales of LNNB‐CR. The “left hemispheric” tasks tended to be more strongly correlated with each other, and less strongly correlated with “right hemispheric” tasks. These data were interpreted as supportive of the notion that RD children display similar patterns of general hemispheric specialization as NRD children, but have problems with specific, and predominately left hemispheric, cognitive processes which are critical to reading.     

Chlorpromazine and the lateralisation of the perception of emotion.

In a double-blind design, sixteen volunteer students were administered 50 mg of chlorpromazine or a placebo in tablet form on separate occasions, two hours prior to testing. The test was a lexical decision paradigm involving unilateral presentation of pairs of neutral, positive and negative emotional words and nonwords to the left or right visual fields. Reaction time to identify words and nonwords was recorded. Neutral stimuli were processed faster in the left hemisphere, while negative stimuli were processed faster in the right hemisphere. Chlorpromazine improved speed of response for neutral stimuli presented to the right hemisphere and for affective stimuli presented to the left hemisphere. Thus chlorpromazine seems to benefit right hemisphere processing of nonaffective stimuli and benefit left hemisphere processing of affective stimuli. Chlorpromazine appeared to have a different impact on neutral and affective words, and on the right and the left hemispheres. The general effect of chlorpromazine was to reduce lateralisation. It was suggested that this occurred because chlorpromazine blocked dopamine and possibly other neurotransmitters.     

Modulation of the neural network involved in the processing of anger prosody: the role of task-relevance and social phobia

Individuals with social phobia display neural hyperactivation towards angry facial expressions. However, it is uncertain whether they also show abnormal brain responses when processing angry voices. In an event-related functional magnetic resonance imaging study, we investigated brain responses to neutral and angry voices in 12 healthy control participants and 12 individuals with social phobia when emotional prosody was either task-relevant or task-irrelevant. Regardless of task, both phobic and non-phobic participants recruited a network comprising frontotemporal regions, the amygdala, the insula, and the striatum, when listening to angry compared to neutral prosody. Across participants, increased activation in orbitofrontal cortex during task-relevant as compared to task-irrelevant emotional prosody processing was found. Compared to healthy controls, individuals with social phobia displayed significantly stronger orbitofrontal activation in response to angry versus neutral voices under both task conditions. These results suggest a disorder-associated increased involvement of the orbitofrontal cortex in response to threatening voices in social phobia.     

What does the dot‐probe task measure? A reverse correlation analysis of electrocortical activity

The dot‐probe task is considered a gold standard for assessing the intrinsic attentive selection of one of two lateralized visual cues, measured by the response time to a subsequent, lateralized response probe. However, this task has recently been associated with poor reliability and conflicting results. To resolve these discrepancies, we tested the underlying assumption of the dot‐probe task—that fast probe responses index heightened cue selection—using an electrophysiological measure of selective attention. Specifically, we used a reverse correlation approach in combination with frequency‐tagged steady‐state visual potentials (ssVEPs). Twenty‐one participants completed a modified dot‐probe task in which each member of a pair of lateralized face cues, varying in emotional expression (angry‐angry, neutral‐angry, neutral‐neutral), flickered at one of two frequencies (15 or 20 Hz), to evoke ssVEPs. One cue was then replaced by a response probe, and participants indicated the probe orientation (0° or 90°). We analyzed the ssVEP evoked by the cues as a function of response speed to the subsequent probe (i.e., a reverse correlation analysis). Electrophysiological measures of cue processing varied with probe hemifield location: Faster responses to left probes were associated with weak amplification of the preceding left cue, apparent only in a median split analysis. By contrast, faster responses to right probes were systematically and parametrically predicted by diminished visuocortical selection of the preceding right cue. Together, these findings highlight the poor validity of the dot‐probe task, in terms of quantifying intrinsic, nondirected attentive selection irrespective of probe/cue location.     

Contralateral white noise selectively changes left human auditory cortex activity in a lexical decision task

In a previous study, we hypothesized that the approach of presenting information-bearing stimuli to one ear and noise to the other ear may be a general strategy to determine hemispheric specialization in auditory cortex (AC). In that study, we confirmed the dominant role of the right AC in directional categorization of frequency modulations by showing that fMRI activation of right but not left AC was sharply emphasized when masking noise was presented to the contralateral ear. Here, we tested this hypothesis using a lexical decision task supposed to be mainly processed in the left hemisphere. Subjects had to distinguish between pseudowords and natural words presented monaurally to the left or right ear either with or without white noise to the other ear. According to our hypothesis, we expected a strong effect of contralateral noise on fMRI activity in left AC. For the control conditions without noise, we found that activation in both auditory cortices was stronger on contralateral than on ipsilateral word stimulation consistent with a more influential contralateral than ipsilateral auditory pathway. Additional presentation of contralateral noise did not significantly change activation in right AC, whereas it led to a significant increase of activation in left AC compared with the condition without noise. This is consistent with a left hemispheric specialization for lexical decisions. Thus our results support the hypothesis that activation by ipsilateral information-bearing stimuli is upregulated mainly in the hemisphere specialized for a given task when noise is presented to the more influential contralateral ear.     

The voices of wrath: brain responses to angry prosody in meaningless speech

We report two functional magnetic resonance imaging experiments showing enhanced responses in human middle superior temporal sulcus for angry relative to neutral prosody. This emotional enhancement was voice specific, unrelated to isolated acoustic amplitude or frequency cues in angry prosody, and distinct from any concomitant task-related attentional modulation. Attention and emotion seem to have separate effects on stimulus processing, reflecting a fundamental principle of human brain organization shared by voice and face perception.     

Automatic emotion regulation in response inhibition: The temporal dynamics of emotion counter‐regulation during a go/no‐go task

Recent behavioral studies indicate that emotion counter‐regulation automatically allocates attention to events that are opposite in the valence to the experienced emotional state. The present study explored the effect of emotion counter‐regulation on response inhibition by using ERPs in a go/no‐go paradigm. We recruited 58 subjects and randomly assigned them to either the angry priming group (watching Nanjing Massacre movie clips) or the neutral priming group (watching “mending a computer” movie clips). The behavioral results revealed that participants in the angry priming group responded significantly more accurately to go happy and no‐go angry faces than go angry and no‐go happy faces. The analyses of ERPs revealed that the amplitudes of the no‐go N2 and no‐go P3 were significantly larger for the happy faces than for the angry faces in the angry priming group. However, no such effects were found in the neutral priming group. These results suggest that highly aroused angry emotion could prompt a priority response to happy emotion stimuli and restrict the responses to angry emotion stimuli through emotion counter‐regulation.     

Tripeptidyl peptidase-I is essential for the degradation of sulphated cholecystokinin-8 (CCK-8S) by mouse brain lysosomes

The prioritized processing of threat is suggested to be motivated by anxiety, regulated by the parasympatheticus, and biased to the right hemisphere. However, according to an anterior dimensional model of negative affect this is unlikely to be true when threat is of social origin. Social threat is communicated by the angry facial expression, and recent research indicates that prioritized processing of angry faces is motivated by anger. Anger is a sympathetically dominated emotion, and for its expression and experience, neuroimaging data have demonstrated anterior lateralization to the left hemisphere. To scrutinize the above diverging statements, suprathreshold low-frequency repetitive transcranial magnetic stimulation (rTMS) was applied over the right and the left prefrontal cortex (PFC) of ten healthy subjects during 15min continuously, and the subsequent effects on sympathetic and parasympathetic activity of the heart, and selective attention to angry facial expressions were investigated. Combined rTMS-neuroimaging studies have shown contralateral excitation after unilateral supratheshold low-frequency rTMS, hence the strengthening of contralaterally mediated emotion functions. The earlier reported increases in selective attention to angry facial expressions after right-PFC rTMS were found to be accompanied by and significantly associated with elevations in sympathetic activity. Our data suggest that a left-PFC lateralized, sympathetic mechanism directs attention towards the angry facial expression.     

Lateralized effects of prefrontal repetitive transcranial magnetic stimulation on emotional working memory

Little is known about the neural correlates underlying the integration of working memory and emotion processing. We investigated the effects of low-frequency repetitive transcranial magnetic stimulation (rTMS) applied over the left or right dorsolateral prefrontal cortex (DLPFC) on emotional working memory. In a sham-controlled crossover design, participants performed an emotional 3-back task (EMOBACK) at baseline and after stimulation (1 Hz, 15 min, 110 % of the resting motor threshold) in two subsequent sessions. Stimuli were words assigned to the distinct emotion categories fear and anger as well as neutral words. We found lateralized rTMS effects in the EMOBACK task accuracy for fear-related words, with enhanced performance after rTMS applied over the right DLPFC and impaired performance after rTMS applied over the left DLPFC. No significant stimulation effect could be found for anger-related and neutral words. Our findings are the first to demonstrate a causal role of the right DLPFC in working memory for negative, withdrawal-related words and provide further support for a hemispheric lateralization of emotion processing.