Distinct and common mechanisms of cross-model semantic conflict and response conflict in an auditory relevant task.

The mechanisms of semantic conflict and response conflict in the Stroop task have mainly been investigated in the visual modality. However, the understanding of these mechanisms in cross-modal modalities remains limited. In this electroencephalography (EEG) study, an audiovisual 2-1 mapping Stroop task was utilized to investigate whether distinct and/or common neural mechanisms underlie cross-modal semantic conflict and response conflict. The response time data showed significant effects on both cross-modal semantic and response conflicts. Interestingly, the magnitude of semantic conflict was found to be smaller in the fast response time bins than in the slow response time bins, whereas no such difference was observed for response conflict. The EEG data demonstrated that cross-modal semantic conflict specifically increased the N450 amplitude. However, cross-modal response conflict specifically enhanced theta band power and theta phase synchronization between the medial frontal cortex (MFC) and lateral prefrontal electrodes as well as between the MFC and motor electrodes. In addition, both cross-modal semantic conflict and response conflict led to a decrease in P3 amplitude. Taken together, these findings provide cross-modal evidence for domain-specific mechanism in conflict detection and suggest both domain-specific and domain-general mechanisms exist in conflict resolution.

Prepared to stop: how sense of agency in a preceding trial modulates inhibitory control in the current trial.

Feeling in control of actions and events can enhance motivation for further actions. How this sense of agency (SoA) in fact influences flexible motor control remains poorly understood. Here, we investigated the effect of SoA on subsequent response inhibition in a modified go/no-go task with EEG recordings. We manipulated participants' SoA by varying the presence, predictability, and emotional valence of a visual outcome for a given motor action. When participants unexpectedly did not receive any visible outcome following their action on trial n - 1, they exhibited slower responses and lower hit rates to the go signal but higher rates of successful inhibition to the no-go signal on trial n, regardless of the emotional valence of the expected action outcome. Furthermore, enhanced inhibitory tendencies were accompanied by reduced N2 and P3 amplitudes, midfrontal theta power, and theta synchronization between midfrontal and medial to parietal areas, indicating that less top-down control is required for successful response inhibition on trial n after experiencing low SoA on trial n - 1. These findings suggest that feeling less in control in a preceding trial makes it easier to implement inhibitory control in the current trial, thereby providing new insights into the role of SoA in goal-directed behavior.

Ready to go: Higher sense of agency enhances action readiness and reduces response inhibition.

Sense of agency is the subjective feeling of being in control of one's actions and their effects. Many studies have elucidated the cognitive and sensorimotor processes that drive this experience. However, less is known about how sense of agency influences flexible cognitive and motor control. Here, we investigated the effect of sense of agency on subsequent action regulation using a modified Go/No-Go task. In Experiment 1, we modulated participants' sense of agency by varying the occurrence of action outcomes (present vs. absent) both locally on a trial-by-trial basis and globally in terms of the overall probability of action outcomes within a block of trials (high vs. low). Importantly, we investigated how this manipulation influenced participants' responses to subsequent Go, No-Go, or Free-Choice cues. When participants' previous action led to an outcome (i.e., a happy face) compared with no outcome, they responded more accurately and faster to Go cues, reacted less accurately to No-Go cues, as well as made go decisions more frequently and faster to Free-Choice cues. These effects were even stronger when action outcomes occurred more frequently overall in a given block or in several previous trials. Experiment 2 further demonstrated that the effects of action outcome manipulation on subsequent action regulation were independent of the emotional valence of the action outcome (i.e., a happy or an angry face). Our results suggest that a higher sense of agency as induced by the presence of action outcomes enhanced action readiness and suppressed response inhibition. These findings highlight the impact of the control felt on the control used in action regulation, thereby providing new insights into the functional significance of the sense of agency on human behavior.

Culture-sex interaction in self-report empathy: The theory and meta-analyses.

Empathy is sharing and understanding others' emotions. Recently, researchers identified larger Western-Asian cultural differences in self-report empathy with females relative to males (i.e., the culture-sex interaction theory). Neglecting this phenomenon, previous researchers focused on identifying the cultural impact on empathy per se and reported divergent results. This meta-analysis aims to reveal the heterogeneity of the earlier publications and decode the heterogeneity as per the culture-sex interaction. The current results suggested the following: First, the cultural impact on empathy increased along with three sex stratification categories (male-only, mixed-sex, and female-only, in that order). Second, the effect size statistically differed between the binary classifications of sex (female-only > male-only). Third, the mixed-sex samples' effect size was positively regressed on the samples' sex ratio (i.e., percentage of females). The current results revealed the heterogeneity of previous publications and highlighted the significance of the culture-sex interaction effect on empathy for future investigations.

Multisensory integration of anticipated cardiac signals with visual targets affects their detection among multiple visual stimuli.

Many studies have elucidated the multisensory processing of different exteroceptive signals (e.g., auditory-visual stimuli), but less is known about the multisensory integration of interoceptive signals with exteroceptive information. Here, we investigated the perceptual outcomes and electrophysiological brain mechanisms of cardio-visual integration by using participants' electrocardiogram signals to control the color change of a visual target in dynamically changing displays. Reaction times increased when the target change coincided with strong cardiac signals concerning the state of cardiovascular arousal (i.e., presented at the end of ventricular systole), compared to when the target change occurred at a time when cardiac arousal was relatively low (i.e., presented at the end of ventricular diastole). Moreover, the concurrence of the target change and cardiac arousal signals modulated the event-related potentials and the beta power in an early period (~100 ms after stimulus onset), and decreased the N2pc and the beta lateralization in a later period (~200 ms after stimulus onset). Our results suggest that the multisensory integration of anticipated cardiac signals with a visual target negatively affects its detection among multiple visual stimuli, potentially by suppressing sensory processing and reducing attention toward the visual target. This finding highlights the role of cardiac information in visual processing and furthers our understanding of the brain dynamics underlying multisensory perception involving both interoception and exteroception.

Response inhibition is disrupted by interoceptive processing at cardiac systole.

The present study investigated how cardiac signals influence response inhibition at both behavioral and electrophysiological levels by using participants' electrocardiogram signals to control the occurrence of events in a stop-signal task, in which the go cue was unpredictably followed by a stop signal requiring the cancellation of the prepotent response. We observed prolonged stop-signal reaction times, reduced stop-signal P3 amplitudes, and higher heartbeat evoked potential amplitudes when the stop signal was presented at cardiac systole, compared to presentation randomly within the cardiac cycle. These effects were independent of the emotional attribute of the stop signal (i.e., emotional facial expression change or non-emotional color change). Our results suggest that coupling stop signals to peripheral autonomic cardiac signals has an impeding effect on response inhibition, probably via shifting attention from exteroception to interoception. Our findings help clarify the precise impact of interoceptive signals on inhibitory control.

Different priming effects of empathy on neural processing associated with firsthand pain and nonpain perception.

The shared-representation model of empathy is still debated. One of the major questions is whether empathy-eliciting stimuli depicting others' pain selectively activate the representations of self-pain. To address this issue, we assessed the priming effects of empathy-eliciting pictures on firsthand pain and nonpain perception, as well as its associated neural processing. In Experiment 1, when compared with nonpainful pictures depicting individuals' body parts with no injury, participants primed by painful pictures showing individuals' body parts with injury reported higher ratings for perceived intensity, unpleasantness, and salience of nociceptive and auditory stimuli, but they only exhibited increased N2 amplitude in response to nociceptive stimuli. In Experiment 2, the results from another group of participants replicated the observations of Experiment 1 and validated the findings in the non-nociceptive somatosensory modality. Importantly, participants' concern ratings for priming pictures predicted their unpleasantness ratings for subsequent nociceptive stimuli, while participants' attention ratings predicted their unpleasantness ratings for subsequent auditory and tactile stimuli. This finding implies that empathy for pain might influence pain and nonpain perception via different psychological mechanisms. In summary, our findings highlight the existence of pain-selective representations in empathy for pain and contribute to a better understanding of the shared-representation model of empathy.

Can self-pain sensitivity quantify empathy for others' pain?

Empathy is essential for the survival of social species. In many studies, especially those with animal models, empathy for pain was evaluated by the modulation of pain sensitivity. However, the relationship between pain sensitivity and empathy for pain is not well established. Here, by performing two experiments, we aimed to investigate their relationship at both behavioral and electrophysiological levels. In Experiment 1, we characterized individual pain sensitivity using pain threshold and tolerance in a cold pressor test, self-report empathy using Interpersonal Reactivity Index, and pain-related psychological factors, including pain-related anxiety, depression, pain catastrophizing, and pain-related fear, using well-validated questionnaires. We observed that pain sensitivity was positively correlated with emotional empathy, and their relationship was mediated by pain-related anxiety, pain catastrophizing, and pain-related fear. In Experiment 2, we quantified empathy for pain using pain intensity and unpleasantness as well as event-related potentials (ERPs) in an empathy for pain task. Positive correlations were observed between pain sensitivity and psychophysiological empathic responses (i.e., the P3 component and the late positive potential in ERPs), and their relationship was mediated by pain-related fear. These results suggested that being influenced by some pain-related psychological factors, individuals with higher pain sensitivity tended to have stronger empathy for pain, manifested as stronger emotional reactions to others' pain. Our results indicated that the conventional strategy of using pain sensitivity to quantify empathy should be treated with caution, as their relationship could be disturbed by experimental manipulations or pathological modulations that could influence individual emotional states or cognitive processes.

Impact Factors of Empathy in Mainland Chinese Youth.

Empathy was investigated in 592 Mainland Chinese youth using the Interpersonal Reactivity Index. Participants' empathy-related information covering demographic traits, emotional wellness, as well as academic and social problems were recorded. Results of Classification and Regression Tree (CART) analysis showed that emotional empathy, cognitive empathy, and empathy-related personal distress was impacted by inherited traits (e.g., sex), acquired traits (e.g., study major), and a combination of both aspects, respectively. Moreover, empathy was found to be higher in youth in a vulnerable social position (i.e., outlander, female, and ethnic minority) than those in a dominant one (i.e., local, male, and ethnic majority). It was also found that personal distress, rather than empathy, was significantly correlated with academic, social, and emotional problems in the youth cohort. Hence, the current study provided an innovative observation of the relationships between empathy, personal distress, ethnicity, social vulnerability, wellness, study major, and other key characteristics in Mainland Chinese youth.

Transcutaneous Electrical Nerve Stimulation in Relieving Neuropathic Pain: Basic Mechanisms and Clinical Applications.

PURPOSE OF REVIEW: Transcutaneous electrical nerve stimulation (TENS) is widely used as a non-pharmacological approach for pain relief in a variety of clinical conditions. This manuscript aimed to review the basic mechanisms and clinical applications regarding the use of TENS for alleviating the peripheral (PNP) and central neuropathic pain (CNP). RECENT FINDINGS: Basic studies on animal models showed that TENS could alleviate pain by modulating neurotransmitters and receptors in the stimulation site and its upper levels, including the spinal cord, brainstem, and brain. Besides, many clinical studies have investigated the efficacy of TENS in patients with CNP (caused by spinal cord injury, stroke, or multiple sclerosis) and PNP (induced by diabetes, cancer, or herpes zoster). Most clinical trials have demonstrated the efficacy of TENS in attenuating neuropathic pain and suggested that appropriate stimulation parameters (e.g., stimulation frequency and intensity) were critical to improving the analgesic effects of TENS. However, there are some conflicting findings related to the efficacy of TENS in relieving neuropathic pain. With optimized stimulation parameters, TENS would be effective in attenuating neuropathic pain. To obtain sufficient evidence to support the use of TENS in the clinic, researchers recommended performing multicenter clinical trials with optimized TENS protocols for the treatment of various CNP and PNP.

Evaluating Cortical Alterations in Patients With Chronic Back Pain Using Neuroimaging Techniques: Recent Advances and Perspectives.

Chronic back pain (CBP) is a leading cause of disability and results in considerable socio-economic burdens worldwide. Although CBP patients are commonly diagnosed and treated with a focus on the "end organ dysfunction" (i.e., peripheral nerve injuries or diseases), the evaluation of CBP remains flawed and problematic with great challenges. Given that the peripheral nerve injuries or diseases are insufficient to define the etiology of CBP in some cases, the evaluation of alterations in the central nervous system becomes particularly necessary and important. With the development of advanced neuroimaging techniques, extensive studies have been carried out to identify the cortical abnormalities in CBP patients. Here, we provide a comprehensive overview on a series of novel findings from these neuroimaging studies to improve our understanding of the cortical abnormalities originated in the disease. First, CBP patients normally exhibit central sensitization to external painful stimuli, which is indexed by increased pain sensitivity and brain activations in pain-related brain regions. Second, long-term suffering from chronic pain leads to emotional disorders, cognitive impairments, and the abnormalities of the relevant brain networks among CBP patients. Third, CBP is associated with massive cortical reorganization, including structural, functional, and metabolic brain changes. Overall, a deep insight into the neural mechanisms underlying the development and outcome of CBP through more sophisticated neuroimaging investigations could not only improve our current understanding of the etiology of CBP but also facilitate the diagnosis and treatment of CBP based on precision medicine.