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

Social threat avoidance depends on action-outcome predictability

Avoiding threatening individuals is pivotal for adaptation to our social environment. Yet, it remains unclear whether social threat avoidance is subtended by goal-directed processes, in addition to stimulus-response associations. To test this, we manipulated outcome predictability during spontaneous approach/avoidance decisions from avatars displaying angry facial expressions. Across three virtual reality experiments, we showed that participants avoided more often when they could predict the outcome of their actions, indicating goal-directed processes. However, above-chance avoidance rate when facing unpredictable outcomes suggested that stimulus-response associations also played a role. We identified two latent classes of participants: the "goal-directed class" showed above-chance avoidance only in the predictable condition, while the "stimulus-response class" showed no credible difference between conditions but had a higher overall avoidance rate. The goal-directed class exhibited greater cardiac deceleration in the predictable condition, associated with better value integration in decision-making. Computationally, this class had an increased drift-rate in the predictable condition, reflecting increased value estimation of threat avoidance. In contrast, the stimulus-response class showed higher responsiveness to threat, indicated by increased drift-rate for avoidance and increased muscular activity at response time. These results support the central role of goal-directed processes in social threat avoidance and reveal its physiological and computational correlates.

Volition and control in law and in brain science: neurolegal translation of a foundational concept

The law assumes that healthy adults are generally responsible for their actions and have the ability to control their behavior based on rational and moral principles. This contrasts with some recent neuroscientific accounts of action control. Nevertheless, both law and neuroscience acknowledge that strong emotions including fear and anger may "trigger" loss of normal voluntary control over action. Thus, "Loss of Control" is a partial defense for murder under English law, paralleling similar defenses in other legal systems. Here we consider the neuroscientific evidence for such legal classifications of responsibility, particularly focussing on how emotional states modulate voluntary motor control and sense of agency. First, we investigate whether neuroscience could contribute an evidence-base for law in this area. Second, we consider the societal impact of some areas where legal thinking regarding responsibility for action diverges from neuroscientific evidence: should we be guided by normative legal traditions, or by modern understanding of brain functions? In addressing these objectives, we propose a translation exercise between neuroscientific and legal terms, which may assist future interdisciplinary research.

Prioritized neural processing of social threats during perceptual decision-making

Emotional signals, notably those signaling threat, benefit from prioritized processing in the human brain. Yet, it remains unclear whether perceptual decisions about the emotional, threat-related aspects of stimuli involve specific or similar neural computations compared to decisions about their non-threatening/non-emotional components. We developed a novel behavioral paradigm in which participants performed two different detection tasks (emotion vs. color) on the same, two-dimensional visual stimuli. First, electroencephalographic (EEG) activity in a cluster of central electrodes reflected the amount of perceptual evidence around 100 ms following stimulus onset, when the decision concerned emotion, not color. Second, participants' choice could be predicted earlier for emotion (240 ms) than for color (380 ms) by the mu (10 Hz) rhythm, which reflects motor preparation. Taken together, these findings indicate that perceptual decisions about threat-signaling dimensions of facial displays are associated with prioritized neural coding in action-related brain regions, supporting the motivational value of socially relevant signals.

The Impact of the Perception of Primary Facial Emotions on Corticospinal Excitability

The link between emotional experience and motor body responses has long been acknowledged. A well-established approach to exploring the effect of the perception of emotional stimuli on the motor system is measuring variations in the excitability of the corticospinal tract (CSE) through motor-evoked potentials (MEP) elicited via transcranial magnetic stimulation (TMS). Previous evidence has indicated a selective increase in MEP amplitude while participants view emotional stimuli, such as emotional facial expressions, compared to neutral cues. However, it is still not clear whether this effect depends on the specific emotional meaning conveyed by the stimulus. In the present study, we explored whether viewing faces expressing the primary emotions compared to faces with a neutral expression affects individuals' CSE, measured using TMS-elicited MEPs. Specifically, we elicited MEPs from the left motor cortex (M1) while participants passively viewed the same faces expressing either anger, fear, disgust, happiness, sadness, surprise, and no emotion (in different blocks). We found that the observation of fearful, angry, disgusted, and happy facial expressions was associated with a significant increase in the MEPs' amplitude compared to neutral facial expressions, with a comparable enhancement in the CSE occurring across these emotions. In turn, viewing sad and surprised faces did not modulate the CSE. Overall, our findings suggest that only facial expressions that signal (real or potential) danger or a rewarding stimulus, but not emotional facial expressions per se, are capable of activating action-related mechanisms.

Mind matters: A narrative review on affective state-dependency in non-invasive brain stimulation

Variability in findings related to non-invasive brain stimulation (NIBS) have increasingly been described as a result of differences in neurophysiological state. Additionally, there is some evidence suggesting that individual differences in psychological states may correlate with the magnitude and directionality of effects of NIBS on the neural and behavioural level. In this narrative review, it is proposed that the assessment of baseline affective states can quantify non-reductive properties which are not readily accessible to neuroscientific methods. Particularly, affective-related states are theorized to correlate with physiological, behavioural and phenomenological effects of NIBS. While further systematic research is needed, baseline psychological states are suggested to provide a complementary cost-effective source of information for understanding variability in NIBS outcomes. Implementing measures of psychological state may potentially contribute to increasing the sensitivity and specificity of results in experimental and clinical NIBS studies.

Trait anger representation in microstructural white matter tracts: A diffusion MRI study

BACKGROUND

Understanding the microstructure of the brain that underlies emotions is of pivotal importance for psychology and psychiatry. Herein, we investigated white matter (WM) tracts associated with anger using the diffusion magnetic resonance imaging (DMRI) connectometry approach while exploring potential sex differences.

METHODS

225 healthy participants from the LEMON database were evaluated using the State-Trait Anger Expression Inventory (STAXI). WM images were prepared and analyzed with DMRI. Multiple regression models were fitted to address the correlation of local connectomes with STAXI components with age and handedness as covariates.

RESULTS

There were no statistically significant differences in state anger and trait anger between males and females (p = 0.55 and 0.30, respectively). DMRI connectometry revealed that quantitative anisotropy (QA) values in the bilateral corticospinal tract (CST), splenium of corpus callosum (SCC), middle cerebellar peduncle, left inferior cerebellar peduncle, left cingulum, and left fornix were negatively correlated with trait anger and trait anger temperament (TAT) in males. In contrast, the QA values in the bilateral CST and SCC showed a positive correlation with trait anger and TAT in females, which, however, did not reach statistical significance.

LIMITATIONS

The cross-sectional design and self-reported measures of anger limit the generalizability of our results.

CONCLUSIONS

This is the first DMRI connectometry study to investigate WM circuits involved in anger. We found that the pathways associated with the limbic system and movement-related regions were involved in trait anger and anger expression in men, while no brain pathways showed a significant relationship with anger in women.

The cognitive neural mechanism of response inhibition and error processing to fearful expressions in adolescents with high reactive aggression

Reactive aggression in adolescents is characterized by high levels of impulsivity. This is associated with deficits in response inhibition and error processing and spontaneous emotion-driven responses to a perceived threat. However, the characteristics and cognitive neural mechanisms of response inhibition and error processing to indirect threat in adolescents with high levels of reactive aggression are unclear. This study explored the characteristics and cognitive neural mechanisms of response inhibition and error processing to fearful expressions in adolescents with high levels of reactive aggression using an emotional Go/No-Go paradigm combined with ERP recordings. Adolescents with high levels of reactive aggression (n = 31) and a control group (n = 30) took part in this study. Results showed that when presented with fearful expressions, adolescents with high levels of reactive aggression showed a smaller No-Go P3 effect and smaller ERN amplitudes following commission errors on the No-Go task than the control group. Results suggested that when presented with fearful expressions, adolescents with high levels of reactive aggression have impaired response inhibition in the later stage of actual inhibitory control of the motor system and impaired error processing in the early stage of fast and automatic initial error detection.

Face emotional expressions influence interhemispheric inhibition

The processing of face expressions is a key ability to perform social interactions. Recently, it has been demonstrated that the excitability of the hand primary motor cortex (M1) increases following the view of negative faces expressions. Interhemispheric interactions and sensory-motor integration are cortical processes involving M1, which are known to be modulated by emotional and social behaviors. Whether these processes may mediate the effects of face emotional expressions on M1 excitability is unknown. Therefore, the aim of this study was to investigate the influence of the passive viewing of face emotional expressions on M1 interhemispheric connections and sensory-motor integration using standardized transcranial magnetic stimulation (TMS) protocols. Nineteen healthy subjects participated in the study. Interhemispheric inhibition (IHI) and short-afferent inhibition (SAI) were probed in the right first dorsal interosseous (FDI) muscle 300 ms after the randomized presentation of seven different face expressions (neutral, sadness, fear, disgust, surprise and happiness). Results showed a significantly reduced IHI following the passive viewing of fearful faces compared to neutral (p = .001) and happy (p = .035) faces and following the view of sad faces compared to neutral faces (p = .008). No effect of emotional faces was detected on SAI. Data suggest that sensory-motor integration process does not mediate the increased excitability of M1 induced by the view of negative face expressions. By contrast, it may be underpinned by a depression of IHI, which from a functional point of view may promote symmetrical avoiding movements of the hands in response to aversive stimuli.

Faces emotional expressions: from perceptive to motor areas in aged and young subjects

The role of age in perception and production of facial expressions is still unclear. Therefore, this work compared, in aged and young subjects, the effects of passive viewing of faces expressing different emotions on perceptive brain regions, such as occipital and temporal cortical areas and on the primary motor cortex (M1) innervating lower face muscles. Seventeen young (24.41 ± 0.71 yr) and seventeen aged (63.82 ± 0.99 yr) subjects underwent recording of event-related potentials (ERP), of motor potentials evoked by transcranial magnetic stimulation of face M1 in the depressor anguli oris muscle and reaction time assessment. In both groups, the P100 and N170 waves, as well as short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) were probed in face M1 after 300 ms from the presentation of images reporting faces expressing happy, sad, and neutral emotions. ERP data evidenced a major involvement of the right hemisphere in perceptual processing of faces, regardless of age. Compared with young subjects, the aged group showed a delayed N170 wave and a smaller P100 wave following the view of sad but not happy or neutral expressions, along with less accuracy and longer reaction times for recognition of the emotion expressed by faces. Aged subjects presented less SICI than young subjects, but facial expressions of happiness increased the excitability of face M1 with no differences between groups. In conclusion, data suggest that encoding of sad face expressions is impaired in the aged compared with the young group, whereas perception of happiness and its excitatory effects on face M1 remains preserved.NEW & NOTEWORTHY This study shows that aged subjects have less visual attention and impaired perception for sad, but not for happy, face expressions. Conversely, the view of happy, but not sad, faces increases excitability in face M1 bilaterally, regardless of age. The impaired attention for sad expressions, the preserved perception of faces expressing happiness, along with the enhancing effects of the latter on face M1 excitability, likely makes the aged subjects more motivated in approaching positive emotions.

Early Right Motor Cortex Response to Happy and Fearful Facial Expressions: A TMS Motor-Evoked Potential Study

The ability to rapidly process others' emotional signals is crucial for adaptive social interactions. However, to date it is still unclear how observing emotional facial expressions affects the reactivity of the human motor cortex. To provide insights on this issue, we employed single-pulse transcranial magnetic stimulation (TMS) to investigate corticospinal motor excitability. Healthy participants observed happy, fearful and neutral pictures of facial expressions while receiving TMS over the left or right motor cortex at 150 and 300 ms after picture onset. In the early phase (150 ms), we observed an enhancement of corticospinal excitability for the observation of happy and fearful emotional faces compared to neutral expressions specifically in the right hemisphere. Interindividual differences in the disposition to experience aversive feelings (personal distress) in interpersonal emotional contexts predicted the early increase in corticospinal excitability for emotional faces. No differences in corticospinal excitability were observed at the later time (300 ms) or in the left M1. These findings support the notion that emotion perception primes the body for action and highlights the role of the right hemisphere in implementing a rapid and transient facilitatory response to emotional arousing stimuli, such as emotional facial expressions.

A computational neuroethology perspective on body and expression perception

Survival prompts organisms to prepare adaptive behavior in response to environmental and social threat. However, what are the specific features of the appearance of a conspecific that trigger such adaptive behaviors? For social species, the prime candidates for triggering defense systems are the visual features of the face and the body. We propose a novel approach for studying the ability of the brain to gather survival-relevant information from seeing conspecific body features. Specifically, we propose that behaviorally relevant information from bodies and body expressions is coded at the levels of midlevel features in the brain. These levels are relatively independent from higher-order cognitive and conscious perception of bodies and emotions. Instead, our approach is embedded in an ethological framework and mobilizes computational models for feature discovery.

Right Hemisphere Dominance for Unconscious Emotionally Salient Stimuli

The present review will focus on evidence demonstrating the prioritization in visual processing of fear-related signals in the absence of awareness. Evidence in hemianopic patients without any form of blindsight or affective blindsight in classical terms will be presented, demonstrating that fearful faces, via a subcortical colliculo-pulvinar-amygdala pathway, have a privileged unconscious visual processing and facilitate responses towards visual stimuli in the intact visual field. Interestingly, this fear-specific implicit visual processing in hemianopics has only been observed after lesions to the visual cortices in the left hemisphere, while no effect was found in patients with damage to the right hemisphere. This suggests that the subcortical route for emotional processing in the right hemisphere might provide a pivotal contribution to the implicit processing of fear, in line with evidence showing enhanced right amygdala activity and increased connectivity in the right colliculo-pulvinar-amygdala pathway for unconscious fear-conditioned stimuli and subliminal fearful faces. These findings will be discussed within a theoretical framework that considers the amygdala as an integral component of a constant and continuous vigilance system, which is preferentially invoked with stimuli signaling ambiguous environmental situations of biological relevance, such as fearful faces.

Fearful faces modulate spatial processing in peripersonal space: An ERP study

Peripersonal space (PPS) represents the region of space surrounding the body. A pivotal function of PPS is to coordinate defensive responses to threat. We have previously shown that a centrally-presented, looming fearful face, signalling a potential threat in one's surroundings, modulates spatial processing by promoting a redirection of sensory resources away from the face towards the periphery, where the threat may be expected - but only when the face is presented in near, rather than far space. Here, we use electrophysiological measures to investigate the neural mechanism underlying this effect. Participants made simple responses to tactile stimuli delivered on the cheeks, while watching task-irrelevant neutral or fearful avatar faces, looming towards them either in near or far space. Simultaneously with the tactile stimulation, a ball with a checkerboard pattern (probe) appeared to the left or right of the avatar face. Crucially, this probe could either be close to the avatar face, and thus more central in the participant's vision, or further away from the avatar face, and thus more peripheral in the participant's vision. Electroencephalography was continuously recorded. Behavioural results confirmed that in near space only, and for fearful relative to neutral faces, tactile processing was facilitated by the peripheral compared to the central probe. This behavioural effect was accompanied by a reduction of the N1 mean amplitude elicited by the peripheral probe for fearful relative to neutral faces. Moreover, the faster the participants responded to tactile stimuli with the peripheral probe, relative to the central, the smaller was their N1. Together these results, suggest that fearful faces intruding into PPS may increase expectation of a visual event occurring in the periphery. This fear-induced effect would enhance the defensive function of PPS when it is most needed, i.e., when the source of threat is nearby, but its location remains unknown.

Fear-related signals are prioritised in visual, somatosensory and spatial systems

The human brain has evolved a multifaceted fear system, allowing threat detection to enable rapid adaptive responses crucial for survival. Although many cortical and subcortical brain areas are believed to be involved in the survival circuits detecting and responding to threat, the amygdala has reportedly a crucial role in the fear system. Here, we review evidence demonstrating that fearful faces, a specific category of salient stimuli indicating the presence of threat in the surrounding, are preferentially processed in the fear system and in the connected sensory cortices, even when they are presented outside of awareness or are irrelevant to the task. In the visual domain, we discuss evidence showing in hemianopic patients that fearful faces, via a subcortical colliculo-pulvinar-amygdala pathway, have a privileged visual processing even in the absence of awareness and facilitate responses towards visual stimuli in the intact visual field. Moreover, evidence showing that somatosensory cortices prioritise fearful-related signals, to the extent that tactile processing is enhanced in the presence of fearful faces, will be also reported. Finally, we will review evidence revealing that fearful faces have a pivotal role in modulating responses in peripersonal space, in line with the defensive functional definition of PPS.

TMS over the posterior cerebellum modulates motor cortical excitability in response to facial emotional expressions

Evidence suggests that the posterior cerebellum is involved in emotional processing. Specific mechanisms by which the cerebellum contributes to the perception of and reaction to the emotional state of others are not well-known. It is likely that perceived emotions trigger anticipatory/preparatory motor changes. However, the extent to which the cerebellum modulates the activity of the motor cortex to contribute to emotional processing has not been directly investigated. In this study, we assessed whether the activity of the posterior cerebellum influences the modulation of motor cortical excitability in response to emotional stimuli. To this end, we transiently disrupted the neural activity of the left posterior cerebellum using 1 Hz repetitive transcranial magnetic stimulation (rTMS) and examined its effect on motor cortical excitability witnessed during emotional face processing (in comparison to the effects of sham rTMS). Motor excitability was measured as TMS-based motor evoked potentials (MEPs) recorded from bilateral first dorsal interosseous (FDI) muscles during the viewing of negative emotional (i.e. fearful) and neutral facial expressions. In line with previous evidence, we found that MEP amplitude was increased during the viewing of fearful compared to neutral faces. Critically, when left posterior cerebellar activity was transiently inhibited with 1 Hz rTMS, we observed a reduction in amplitude of MEPs recorded from the contralateral (right) motor cortex during the viewing of emotional (but not neutral) faces. In turn, inhibition of the left posterior cerebellum did not affect the amplitude of MEPs recorded from the ipsilateral motor cortex. Our findings suggest that the posterolateral (left) cerebellum modulates motor cortical response to negative emotional stimuli and may serve as an interface between limbic, cognitive, and motor systems.

The spatial effect of fearful faces in the autonomic response

Peripersonal space (PPS) corresponds to the space around the body and it is defined by the location in space where multimodal inputs from bodily and external stimuli are integrated. Its extent varies according to the characteristics of external stimuli, e.g., the salience of an emotional facial expression. In the present study, we investigated the psycho-physiological correlates of the extension phenomenon. Specifically, we investigated whether an approaching human face showing either an emotionally negative (fearful) or positive (joyful) facial expression would differentially modulate PPS representation, compared to the same face with a neutral expression. To this aim, we continuously recorded the skin conductance response (SCR) of 27 healthy participants while they watched approaching 3D avatar faces showing fearful, joyful or neutral expressions, and then pressed a button to respond to tactile stimuli delivered on their cheeks at three possible delays (visuo-tactile trials). The results revealed that the SCR to fearful faces, but not joyful or neutral faces, was modulated by the apparent distance from the participant's body. SCR increased from very far space to far and then to near space. We propose that the proximity of the fearful face provided a cue to the presence of a threat in the environment and elicited a robust and urgent organization of defensive responses. In contrast, there would be no need to organize defensive responses to joyful or neutral faces and, as a consequence, no SCR differences were found across spatial positions. These results confirm the defensive function of PPS.

Indignation for moral violations suppresses the tongue motor cortex: preliminary TMS evidence

We commonly label moral violations in terms of ‘disgust’, yet it remains unclear whether metaphorical expressions linking disgust and morality are genuinely shared at the cognitive/neural level. Using transcranial magnetic stimulation (TMS), we provide new insights into this debate by measuring motor-evoked potentials (MEPs) from the tongue generated by TMS over the tongue primary motor area (tM1) in a small group of healthy participants presented with vignettes of moral transgressions and non-moral vignettes. We tested whether moral indignation, felt while evaluating moral vignettes, affected tM1 excitability. Vignettes exerted a variable influence on MEPs with no net effect of the moral category. However, in accordance with our recent study documenting reduced tM1 excitability during exposure to pictures of disgusting foods or facial expressions of distaste, we found that the vignettes of highly disapproved moral violations reduced tM1 excitability. Moreover, tM1 excitability and moral indignation were linearly correlated: the higher the moral indignation, the lower the tM1 excitability. Respective changes in MEPs were not observed in a non-oral control muscle, suggesting a selective decrease of tM1 excitability. These preliminary findings provide neurophysiological evidence supporting the hypothesis that morality might have originated from the more primitive experience of oral distaste.

The role of computational and subjective features in emotional body expressions

Humans are experts at recognizing intent and emotion from other people’s body movements; however, the underlying mechanisms are poorly understood. Here, we computed quantitative features of body posture and kinematics and acquired behavioural ratings of these feature descriptors to investigate their role in affective whole-body movement perception. Representational similarity analyses and classification regression trees were used to investigate the relation of emotional categories to both the computed features and behavioural ratings. Overall, postural rather than kinematic features discriminated better between emotional movements for the computed as well as for the behavioural features. In particular, limb angles and symmetry appeared to be the most relevant ones. This was observed independently of whether or not the time-related information was preserved in the computed features. Interestingly, the behavioural ratings showed a clearer distinction between affective movements than the computed counterparts. Finally, the perceived directionality of the movement (i.e. towards or away from the observer) was found to be critical for the recognition of fear and anger.

Happy faces selectively increase the excitability of cortical neurons innervating frowning muscles of the mouth

Although facial muscles are heavily involved in emotional expressions, there is still a lack of evidence about the role of face primary motor cortex (face M1) in the processing of facial recognition and expression. This work investigated the effects of the passive viewing of different facial expressions on face M1 and compared data with those obtained from the hand M1. Thirty healthy subjects were randomly assigned to two groups undergoing transcranial magnetic stimulation (TMS) of face or hand M1. In both groups, short-latency intracortical inhibition (SICI) and intracortical facilitation (ICF) were probed in the depressor anguli oris (DAO) and first dorsal interosseous (FDI) muscles 300 ms after presentation of a picture of a face that expressed happy, sad or neutral emotions. Statistical analysis of SICI showed a non-significant effect of muscle (F_1,28 = 1.903, p = 0.179), but a significant effect of emotion (F_2,56 = 6.860, p = 0.004) and a significant interaction between muscle and emotion (F_2,56 = 5.072, p = 0.015). Post hoc analysis showed that there was a significant reduction of SICI in the DAO muscle after presentation of a face with a happy expression compared with a neutral face (p < 0.001). In the FDI, a significant difference was observed between neutral and sad expressions (p = 0.010) No clear differences in ICF were detected. The different responses of face and hand muscles to emotional stimuli may be due to their functional roles in emotional expression versus protection of the body.

Anger and impulsiveness in migraine patients with and without aura

Background and purpose: Migraine is a common primary headache disorder triggered by internal or external stimuli. Impulsitivity and anger are associated with many neurological and psychiatric disorders. The aim of this study was to investigate the anger and impulsivity in migraine patients with or without aura.Methods: A total of 55 patients aged between 18 and 55, who were diagnosed with episodic migraine (31 with aura and 24 without aura) and 40 healthy controls were enrolled in this prospective cross-sectional study.Migraine diagnosis and classification were based on criteria from the International Classification of Headache Disorders, 3rd edition (beta version). Multidimensional Anger Scale and Barratt Impulsivity Scale-11 were administered to the patient and control groups.Results:Migraine patients with aura, migraine patients without aura and control groups were compared, anger symptoms were significantly higher in migraine patients with aura (p < 0.001), but between these groups there was no significant difference in terms of impulsivity (p = 0.711).Conclusions: It was found that anger symptoms were more common in migraine patients with aura compared to migraine patients without aura and control group, but in impulsitivity there was no difference between groups.Further studies in future investigating the relation between migraine with aura and anger may pave the way for different and more specified treatment approach.

How do you perceive threat? It's all in your pattern of brain activity

Whether subtle differences in the emotional context during threat perception can be detected by multi-voxel pattern analysis (MVPA) remains a topic of debate. To investigate this question, we compared the ability of pattern recognition analysis to discriminate between patterns of brain activity to a threatening versus a physically paired neutral stimulus in two different emotional contexts (the stimulus being directed towards or away from the viewer). The directionality of the stimuli is known to be an important factor in activating different defensive responses. Using multiple kernel learning (MKL) classification models, we accurately discriminated patterns of brain activation to threat versus neutral stimuli in the directed towards context but not during the directed away context. Furthermore, we investigated whether it was possible to decode an individual’s subjective threat perception from patterns of whole-brain activity to threatening stimuli in the different emotional contexts using MKL regression models. Interestingly, we were able to accurately predict the subjective threat perception index from the pattern of brain activation to threat only during the directed away context. These results show that subtle differences in the emotional context during threat perception can be detected by MVPA. In the directed towards context, the threat perception was more intense, potentially producing more homogeneous patterns of brain activation across individuals. In the directed away context, the threat perception was relatively less intense and more variable across individuals, enabling the regression model to successfully capture the individual differences and predict the subjective threat perception.

Angry and Fearful Face Conflict Effects in Post-traumatic Stress Disorder

In the presence of threatening stimuli, post-traumatic stress disorder (PTSD) can manifest as hypervigilance for threat and disrupted attentional control. PTSD patients have shown exaggerated interference effects on tasks using trauma-related or threat stimuli. In studies of PTSD, faces with negative expressions are often used as threat stimuli, yet angry and fearful facial expressions may elicit different responses. The modified Eriksen flanker task, or the emotional face flanker, has been used to examine response interference. We compared 23 PTSD patients and 23 military controls on an emotional face flanker task using angry, fearful and neutral expressions. Participants identified the emotion of a central target face flanked by faces with either congruent or incongruent emotions. As expected, both groups showed slower reaction times (RTs) and decreased accuracy on emotional target faces, relative to neutral. Unexpectedly, both groups showed nearly identical interference effects on fearful and neutral target trials. However, post hoc testing suggested that PTSD patients showed faster RTs than controls on congruent angry faces (target and flanker faces both angry) relative to incongruent, although this finding should be interpreted with caution. This possible RT facilitation effect with angry, but not fearful faces, also correlated positively with self-report measures of PTSD symptoms. These results suggest that PTSD patients may be more vigilant for, or primed to respond to, the appearance of angry faces, relative to fearful, but further study is needed.

Perception of Threatening Intention Modulates Brain Processes to Body Actions: Evidence From Event-Related Potentials

Efficiently perceiving a threatening intention conveyed by others’ bodily actions has great survival value. The current study examined if the human brain is sensitive to differences in intentions that are conveyed via bodily actions. For this purpose, a new intention categorization task was developed in which participants sat in front of a computer screen on which the pictures of highly threatening (HT), moderately threatening (MT), and non-threatening (NT) body actions were presented randomly. Participants were asked to press the corresponding buttons using threatening intention judgment, while event-related potentials (ERPs) were recorded. According to a cluster permutation test, we analyzed N190, N2, EPP (early posterior positivity), and P3. The results showed there was a positive correlation between the amplitude of the EPP induced by three kinds of body actions and the reaction time of the task. The results also revealed that when the deflection of EPP was less positive, the reaction time was shorter. We suggest that EPP might be useful as an index of body intention processing of the brain. The current study revealed that intention perception of body actions modulates brain processing.

Neural Responses to Consciously and Unconsciously Perceived Emotional Faces: A Spinal fMRI Study

Emotional stimuli modulate activity in brain areas related to attention, perception, and movement. Similar increases in neural activity have been detected in the spinal cord, suggesting that this understudied component of the central nervous system is an important part of our emotional responses. To date, previous studies of emotion-dependent spinal cord activity have utilized long presentations of complex emotional scenes. The current study differs from this research by (1) examining whether emotional faces will lead to enhanced spinal cord activity and (2) testing whether these stimuli require conscious perception to influence neural responses. Fifteen healthy undergraduate participants completed six spinal functional magnetic resonance imaging (fMRI) runs in which three one-minute blocks of fearful, angry, or neutral faces were interleaved with 40-s rest periods. In half of the runs, the faces were clearly visible while in the other half, the faces were displayed for only 17 ms. Spinal fMRI consisted of half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences targeting the cervical spinal cord. The results indicated that consciously perceived faces expressing anger elicited significantly more activity than fearful or neutral faces in ventral (motoric) regions of the cervical spinal cord. When stimuli were presented below the threshold of conscious awareness, neutral faces elicited significantly more activity than angry or fearful faces. Together, these data suggest that the emotional modulation of spinal cord activity is most impactful when the stimuli are consciously perceived and imply a potential threat toward the observer.

The Influence of Conscious and Unconscious Body Threat Expressions on Motor Evoked Potentials Studied With Continuous Flash Suppression

The observation of threatening expression in others is a strong cue for triggering an action response. One method of capturing such action responses is by measuring the amplitude of motor evoked potentials (MEPs) elicited with single pulse TMS over the primary motor cortex. Indeed, it has been shown that viewing whole body expressions of threat modulate the size of MEP amplitude. Furthermore, emotional cues have been shown to act on certain brain areas even outside of conscious awareness. In the current study, we explored if the influence of viewing whole body expressions of threat extends to stimuli that are presented outside of conscious awareness in healthy participants. To accomplish this, we combined the measurement of MEPs with a continuous flash suppression task. In experiment 1, participants were presented with images of neutral bodies, fearful bodies, or objects that were either perceived consciously or unconsciously, while single pulses of TMS were applied at different times after stimulus onset (200, 500, or 700 ms). In experiment 2 stimuli consisted of neutral bodies, angry bodies or objects, and pulses were applied at either 200 or 400 ms post stimulus onset. In experiment 1, there was a general effect of the time of stimulation, but no condition specific effects were evident. In experiment 2 there were no significant main effects, nor any significant interactions. Future studies need to look into earlier effects of MEP modulation by emotion body stimuli, specifically when presented outside of conscious awareness, as well as an exploration of other outcome measures such as intracortical facilitation.