Early motor reactivity to observed human body postures is affected by body expression, not gender

Individual differences in intracortical inhibition predict action control when facing emotional stimuli

Efficient inhibitory control in the context of prepotent actions is vital. However, such action inhibition may be profoundly influenced by affective states. Interestingly, research indicates that action control can be either impaired or improved by emotional stimuli. Thus, a great deal of confusion surrounds our knowledge of the complex dynamics subtending emotions and action control. Here, we aimed to investigate whether negative stimuli, even when non-consciously presented and task-irrelevant, can affect action control relative to neutral stimuli. Additionally, we tested whether individual differences in intracortical excitability may predict action control capabilities. To address these issues, we asked participants to complete a modified version of the Stop Signal Task (SST) in which fearful or neutral stimuli were subliminally presented before the go signals as primes. Moreover, we assessed participants' resting-state corticospinal excitability, short intracortical inhibition (SICI), and intracortical facilitation (ICF). Results demonstrated better action control capabilities when fearful stimuli were subliminally presented and interindividual SICI predicted stronger action inhibition capabilities. Taken together, these results shed new light on the intricate dynamics between action, consciousness, and motor control, suggesting that intracortical measures can be used as potential biomarkers of reduced motor inhibition in research and clinical settings.

The role of pre-supplementary motor cortex in action control with emotional stimuli: A repetitive transcranial magnetic stimulation study

Swiftly halting ongoing motor actions is essential to react to unforeseen and potentially perilous circumstances. However, the neural bases subtending the complex interplay between emotions and motor control have been scarcely investigated. Here, we used an emotional stop signal task (SST) to investigate whether specific neural circuits engaged by action suppression are differently modulated by emotional signals with respect to neutral ones. Participants performed an SST before and after the administration of one session of repetitive transcranial magnetic stimulation (rTMS) over the pre-supplementary motor cortex (pre-SMA), the right inferior frontal gyrus (rIFG), and the left primary motor cortex (lM1). Results show that rTMS over the pre-SMA improved the ability to inhibit prepotent action (i.e., better action control) when emotional stimuli were presented. In contrast, action control in a neutral context was fostered by rTMS over the rIFG. No changes were observed after lM1 stimulation. Intriguingly, individuals with higher impulsivity traits exhibited enhanced motor control when facing neutral stimuli following rIFG stimulation. These results further our understanding of the interplay between emotions and motor functions, shedding light on the selective modulation of neural pathways underpinning these processes.

Task-related modulation of motor response to emotional bodies: A TMS motor-evoked potential study

Exposure to emotional body postures during perceptual decision-making tasks has been linked to transient suppression of motor reactivity, supporting the monitoring of emotionally relevant information. However, it remains unclear whether this effect occurs implicitly, i.e., when emotional information is irrelevant to the task. To investigate this issue, we used single-pulse transcranial magnetic stimulation (TMS) to assess motor excitability while healthy participants were asked to categorize pictures of body expressions as emotional or neutral (emotion recognition task) or as belonging to a male or a female actor (gender recognition task) while receiving TMS over the motor cortex at 100 and 125 ms after picture onset. Results demonstrated that motor-evoked potentials (MEPs) were reduced for emotional body postures relative to neutral postures during the emotion recognition task. Conversely, MEPs increased for emotional body postures relative to neutral postures during the gender recognition task. These findings indicate that motor inhibition, contingent upon observing emotional body postures, is selectively associated with actively monitoring emotional features. In contrast, observing emotional body postures prompts motor facilitation when task-relevant features are non-emotional. These findings contribute to embodied cognition models that link emotion perception and action tendencies.

Early modulations of neural oscillations during the processing of emotional body language

The processing of threat-related emotional body language (EBL) has been shown to engage sensorimotor cortical areas early on and induce freezing in the observers' motor system, particularly when observing fearful EBL. To provide insights into the interplay between somatosensory and motor areas during observation of EBL, here, we used high-density electroencephalography (hd-EEG) in healthy humans while they observed EBL stimuli involving fearful and neutral expressions. To capture early sensorimotor brain response, we focused on P100 fronto-central event-related potentials (ERPs) and event-related desynchronization/synchronization (ERD/ERS) in the mu-alpha (8-13 Hz) and lower beta (13-20 Hz) bands over the primary motor (M1) and somatosensory (S1) cortices. Source-level ERP and ERD/ERS analyses were conducted using eLORETA. Results revealed higher P100 amplitudes in motor and premotor channels for 'Neutral' compared with 'Fear'. Additionally, analysis of ERD/ERS showed increased beta band desynchronization in M1 for 'Neutral', and the opposite pattern in S1. Source-level estimation showed significant differences between conditions mainly observed in the beta band over sensorimotor areas. These findings provide high-temporal resolution evidence suggesting that seeing fearful EBL induces early activation of somatosensory areas, which in turn could suppress M1 activity. These findings highlight early dynamics within the observer's sensorimotor system and hint at a sensorimotor mechanism supporting freezing during the processing of EBL.

How Music Moves Us: Music-induced Emotion Influences Motor Learning

Music is an important tool for the induction and regulation of emotion. Although learning a sequential motor behaviour is essential to normal motor function, to our knowledge, the role of music-induced emotion on motor learning has not been explored. Our experiment aimed to determine whether listening to different emotional music could influence motor sequence learning. We focused on two sub-components of motor sequence learning: the acquisition of the order of the elements in the sequence (the "what"), and the ability to carry out the sequence, combining the elements in a single, skilled action (the "how"). Twenty subjects performed a motor sequence-learning task with a digitizing tablet in three different experimental sessions. In each session they executed the task while listening to three different musical pieces, eliciting fearful, pleasant, and neutral mood. Eight targets were presented in a pre-set order and subjects were asked to learn the sequence while moving. Music-induced pleasure had an impact on movement kinematics with onset time and peak velocity decreasing and movement time increasing more with respect to neutral music session. Declarative learning, verbal recall of the sequence order, was improved under emotional manipulation, but only for fear-condition. Results suggest that music-induced emotion can influence both sub-components of motor learning in a different way. Music-induced pleasure may have improved motor components of sequence learning by means of increased striatal dopamine availability whereas music-induced fear may facilitate the recruitment of attentional circuits, thus acting on declarative knowledge of the sequence order.

What is missing in the study of emotion expression?

While approaching celebrations for the 150 years of "The Expression of the Emotions in Man and Animals", scientists' conclusions on emotion expression are still debated. Emotion expression has been traditionally anchored to prototypical and mutually exclusive facial expressions (e.g., anger, disgust, fear, happiness, sadness, and surprise). However, people express emotions in nuanced patterns and - crucially - not everything is in the face. In recent decades considerable work has critiqued this classical view, calling for a more fluid and flexible approach that considers how humans dynamically perform genuine expressions with their bodies in context. A growing body of evidence suggests that each emotional display is a complex, multi-component, motoric event. The human face is never static, but continuously acts and reacts to internal and environmental stimuli, with the coordinated action of muscles throughout the body. Moreover, two anatomically and functionally different neural pathways sub-serve voluntary and involuntary expressions. An interesting implication is that we have distinct and independent pathways for genuine and posed facial expressions, and different combinations may occur across the vertical facial axis. Investigating the time course of these facial blends, which can be controlled consciously only in part, is recently providing a useful operational test for comparing the different predictions of various models on the lateralization of emotions. This concise review will identify shortcomings and new challenges regarding the study of emotion expressions at face, body, and contextual levels, eventually resulting in a theoretical and methodological shift in the study of emotions. We contend that the most feasible solution to address the complex world of emotion expression is defining a completely new and more complete approach to emotional investigation. This approach can potentially lead us to the roots of emotional display, and to the individual mechanisms underlying their expression (i.e., individual emotional signatures).

Positive and negative facial valence perception are modulated differently by eccentricity in the parafovea

Understanding whether people around us are in a good, bad or neutral mood can be critical to our behavior, both when looking directly at them or when they are in our peripheral visual field. However, facial expressions of emotions are often investigated at central visual field or at locations right or left of fixation. Here we assumed that perception of facial emotional valence (the emotion's pleasantness) changes with distance from central visual field (eccentricity) and that different emotions may be influenced differently by eccentricity. Participants (n = 58) judged the valence of emotional faces across the parafovea (≤ 4°, positive (happy), negative (fearful), or neutral)) while their eyes were being tracked. As expected, performance decreased with eccentricity. Positive valence perception was least affected by eccentricity (accuracy reduction of 10-19% at 4°) and negative the most (accuracy reduction of 35-38% at 4°), and this was not a result of speed-accuracy trade-off or response biases. Within-valence (but not across-valence) performance was associated across eccentricities suggesting perception of different valences is supported by different mechanisms. While our results may not generalize to all positive and negative emotions, they indicate that beyond-foveal investigations can reveal additional characteristics of the mechanisms that underlie facial expression processing and perception.

Emotional body postures affect inhibitory control only when task-relevant

A classical theoretical frame to interpret motor reactions to emotional stimuli is that such stimuli, particularly those threat-related, are processed preferentially, i.e., they are capable of capturing and grabbing attention automatically. Research has recently challenged this view, showing that the task relevance of emotional stimuli is crucial to having a reliable behavioral effect. Such evidence indicated that emotional facial expressions do not automatically influence motor responses in healthy young adults, but they do so only when intrinsically pertinent to the ongoing subject's goals. Given the theoretical relevance of these findings, it is essential to assess their generalizability to different, socially relevant emotional stimuli such as emotional body postures. To address this issue, we compared the performance of 36 right-handed participants in two different versions of a Go/No-go task. In the Emotional Discrimination task, participants were required to withhold their responses at the display of emotional body postures (fearful or happy) and to move at the presentation of neutral postures. Differently, in the control task, the same images were shown, but participants had to respond according to the color of the actor/actress' t-shirt, disregarding the emotional content. Results showed that participants made more commission errors (instances in which they moved even though the No-go signal was presented) for happy than fearful body postures in the Emotional Discrimination task. However, this difference disappeared in the control task. Such evidence indicates that, like facial emotion, emotional body expressions do not influence motor control automatically, but only when they are task-relevant.

Stopping in (e)motion: Reactive action inhibition when facing valence-independent emotional stimuli

Emotions are able to impact our ability to control our behaviors. However, it is not clear whether emotions play a detrimental or an advantageous effect on action control and whether the valence of the emotional stimuli differently affects such motor abilities. One way to measure reactive inhibitory control is the stop-signal task (SST), which estimates the ability to cancel outright a response to the presentation of a stop signal by means of the stop signal reaction times (SSRT). Impaired as well as facilitated action control has been found when faced with emotional stimuli such as stop signals in SSTs and mixed results were observed for positive versus negative stimuli. Here, we aimed to investigate these unresolved issues more deeply. Action control capabilities were tested in 60 participants by means of a SST, in which the stop signals were represented by a fearful and a happy body posture together with their neutral counterpart. Results showed that both positive and negative body postures enhanced the ability to suppress an ongoing action compared to neutral body postures. These results demonstrate that emotional valence-independent emotional stimuli facilitate action control and suggest that emotional stimuli may trigger increased sensory representation and/or attentional processing that may have promote stop-signal processing and hence improved inhibitory performance.

The Influence of Vicarious Fear-Learning in “Infecting” Reactive Action Inhibition

Since the dawn of cognitive neuroscience, emotions have been recognized to impact on several executive processes, such as action inhibition. However, the complex interplay between emotional stimuli and action control is not yet fully understood. One way to measure inhibitory control is the stop-signal task (SST), which estimates the ability to cancel outright an action to the presentation of a stop signal by means of the stop-signal reaction times (SSRTs). Impaired as well as facilitated action control has been found when faced with intrinsic emotional stimuli as stop signals in SSTs. Here, we aimed at investigating more deeply the power of negative stimuli to influence our action control, testing the hypothesis that a previously neutral stimulus [i.e., the image of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)], which has been conditioned through vicarious fear learning, has the same impact on reactive action inhibition performance as an intrinsically negative stimulus (i.e., a fearful face or body). Action control capabilities were tested in 90 participants by means of a SST, in which the stop signals were represented by different negative stimuli. Results showed that the SARS-CoV-2 image enhanced the ability to suppress an ongoing action similarly to observing fearful facial expressions or fearful body postures. Interestingly, we found that this effect was predicted by impulsivity traits: for example, the less self-control the participants had, the less they showed emotional facilitation for inhibitory performance. These results demonstrated that vicarious fear learning has a critical impact on cognitive abilities, making a neutral image as threatening as phylogenetically innate negative stimuli and able to impact on our behavioral control.

Sensorimotor inhibition during emotional processing

Visual processing of emotional stimuli has been shown to engage complex cortical and subcortical networks, but it is still unclear how it affects sensorimotor integration processes. To fill this gap, here, we used a TMS protocol named short-latency afferent inhibition (SAI), capturing sensorimotor interactions, while healthy participants were observing emotional body language (EBL) and International Affective Picture System (IAPS) stimuli. Participants were presented with emotional (fear- and happiness-related) or non-emotional (neutral) EBL and IAPS stimuli while SAI was tested at 120 ms and 300 ms after pictures presentation. At the earlier time point (120 ms), we found that fear-related EBL and IAPS stimuli selectively enhanced SAI as indexed by the greater inhibitory effect of somatosensory afferents on motor excitability. Larger early SAI enhancement was associated with lower scores at the Behavioural Inhibition Scale (BIS). At the later time point (300 ms), we found a generalized SAI decrease for all kind of stimuli (fear, happiness or neutral). Because the SAI index reflects integrative activity of cholinergic sensorimotor circuits, our findings suggest greater sensitivity of such circuits during early (120 ms) processing of threat-related information. Moreover, the correlation with BIS score may suggest increased attention and sensory vigilance in participants with greater anxiety-related dispositions. In conclusion, the results of this study show that sensorimotor inhibition is rapidly enhanced while processing threatening stimuli and that SAI protocol might be a valuable option in evaluating emotional-motor interactions in physiological and pathological conditions.

The Neurobiological Correlates of Gaze Perception in Healthy Individuals and Neurologic Patients

The ability to adaptively follow conspecific eye movements is crucial for establishing shared attention and survival. Indeed, in humans, interacting with the gaze direction of others causes the reflexive orienting of attention and the faster object detection of the signaled spatial location. The behavioral evidence of this phenomenon is called gaze-cueing. Although this effect can be conceived as automatic and reflexive, gaze-cueing is often susceptible to context. In fact, gaze-cueing was shown to interact with other factors that characterize facial stimulus, such as the kind of cue that induces attention orienting (i.e., gaze or non-symbolic cues) or the emotional expression conveyed by the gaze cues. Here, we address neuroimaging evidence, investigating the neural bases of gaze-cueing and the perception of gaze direction and how contextual factors interact with the gaze shift of attention. Evidence from neuroimaging, as well as the fields of non-invasive brain stimulation and neurologic patients, highlights the involvement of the amygdala and the superior temporal lobe (especially the superior temporal sulcus (STS)) in gaze perception. However, in this review, we also emphasized the discrepancies of the attempts to characterize the distinct functional roles of the regions in the processing of gaze. Finally, we conclude by presenting the notion of invariant representation and underline its value as a conceptual framework for the future characterization of the perceptual processing of gaze within the STS.

After-Effects of Intermittent Theta-Burst Stimulation Are Differentially and Phase-Dependently Suppressed by α- and β-Frequency Transcranial Alternating Current Stimulation

Intermittent theta-burst stimulation (iTBS) using transcranial magnetic stimulation (TMS) is known to produce excitatory after-effects over the primary motor cortex (M1). Recently, transcranial alternating current stimulation (tACS) at 10 Hz (α) and 20 Hz (β) have been shown to modulate M1 excitability in a phase-dependent manner. Therefore, we hypothesized that tACS would modulate the after-effects of iTBS depending on the stimulation frequency and phase. To test our hypothesis, we examined the effects of α- and β-tACS on iTBS using motor evoked potentials (MEPs). Eighteen and thirteen healthy participants were recruited for α and β tACS conditions, respectively. tACS electrodes were attached over the left M1 and Pz. iTBS over left M1 was performed concurrently with tACS. The first pulse of the triple-pulse burst of iTBS was controlled to match the peak (90°) or trough (270°) phase of the tACS. A sham tACS condition was used as a control in which iTBS was administered without tACS. Thus, each participant was tested in three conditions: the peak and trough of the tACS phases and sham tACS. As a result, MEPs were enhanced after iTBS without tACS (sham condition), as observed in previous studies. α-tACS suppressed iTBS effects at the peak phase but not at the trough phase, while β-tACS suppressed the effects at both phases. Thus, although both types of tACS inhibited the facilitatory effects of iTBS, only α-tACS did so in a phase-dependent manner. Phase-dependent inhibition by α-tACS is analogous to our previous finding in which α-tACS inhibited MEPs online at the peak condition. Conversely, β-tACS reduced the effects of iTBS irrespective of its phase. The coupling of brain oscillations and tACS rhythms is considered important in the generation of spike-timing-dependent plasticity. Additionally, the coupling of θ and γ oscillations is assumed to be important for iTBS induction through long-term potentiation (LTP). Therefore, excessive coupling between β oscillations induced by tACS and γ or θ oscillations induced by iTBS might disturb the coupling of θ and γ oscillations during iTBS. To conclude, the action of iTBS is differentially modulated by neuronal oscillations depending on whether α- or β-tACS is applied.

Frozen in (e)motion: How reactive motor inhibition is influenced by the emotional content of stimuli in healthy and psychiatric populations

Efficient inhibitory control is vital. However, environmental cues can influence motor control especially in an emotional context. One common task to measure inhibitory control is the stop-signal task (SST), which asks participants to respond to go stimuli knowing that on some trials a stop signal will be presented, requiring them to inhibit their response. This paradigm estimates the ability to inhibit already-initiated responses by calculating participants' stop-signal reaction times (SSRT), an index of inhibitory control. Here, we aim to review the existing, often contradictory, evidence on the influence of emotional stimuli on the inhibitory process. We aim to discuss which factors may reveal an interference as well as an advantage of emotional stimuli on action inhibition performance. Finally, we review the existing evidence that has investigated the effect of such stimuli on action inhibition in the psychiatric population. Important factors are the relevance, the intensity and the valence of the emotional stimulus, as well as the affected component of the motor control. From all this evidence, it is clear that understand precisely how emotion is integrated into core executive functions, such as inhibitory control, is essential not only for cognitive neuroscience, but also for refining neurocognitive models of psychopathology.

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.

Memories are not written in stone: Re-writing fear memories by means of non-invasive brain stimulation and optogenetic manipulations

The acquisition of fear associative memory requires brain processes of coordinated neural activity within the amygdala, prefrontal cortex (PFC), hippocampus, thalamus and brainstem. After fear consolidation, a suppression of fear memory in the absence of danger is crucial to permit adaptive coping behavior. Acquisition and maintenance of fear extinction critically depend on amygdala-PFC projections. The robust correspondence between the brain networks encompassed cortical and subcortical hubs involved into fear processing in humans and in other species underscores the potential utility of comparing the modulation of brain circuitry in humans and animals, as a crucial step to inform the comprehension of fear mechanisms and the development of treatments for fear-related disorders. The present review is aimed at providing a comprehensive description of the literature on recent clinical and experimental researches regarding the noninvasive brain stimulation and optogenetics. These innovative manipulations applied over specific hubs of fear matrix during fear acquisition, consolidation, reconsolidation and extinction allow an accurate characterization of specific brain circuits and their peculiar interaction within the specific fear processing.

Modulation of Response Times During Processing of Emotional Body Language

The investigation of how humans perceive and respond to emotional signals conveyed by the human body has been for a long time secondary compared with the investigation of facial expressions and emotional scenes recognition. The aims of this behavioral study were to assess the ability to process emotional body postures and to test whether motor response is mainly driven by the emotional content of the picture or if it is influenced by motor resonance. Emotional body postures and scenes (IAPS) divided into three clusters (fear, happiness, and neutral) were shown to 25 healthy subjects (13 males, mean age ± SD: 22.3 ± 1.8 years) in a three-alternative forced choice task. Subjects were asked to recognize the emotional content of the pictures by pressing one of three keys as fast as possible in order to estimate response times (RTs). The rating of valence and arousal was also performed. We found shorter RTs for fearful body postures as compared with happy and neutral postures. In contrast, no differences across emotional categories were found for the IAPS stimuli. Analysis on valence and arousal and the subsequent item analysis showed an excellent reliability of the two sets of images used in the experiment. Our results show that fearful body postures are rapidly recognized and processed, probably thanks to the automatic activation of a series of central nervous system structures orchestrating the defensive threat reactions, strengthening and supporting previous neurophysiological and behavioral findings in body language processing.