Placebo Effect on Modulating Empathic Pain: Reduced Activation in Posterior Insula

Empathic pain: Underlying neural mechanism

Empathy is usually regarded as the ability to perceive the emotional state of others, which is an altruistic motivation to promote prosocial behavior and thus plays a key role in human life and social development. Empathic pain-the capacity to feel and understand the pain of others-constitutes a significant aspect in the study of empathy behaviors. For an extended duration, investigations into empathic pain have predominantly centered on human neuroimaging studies. Fortunately, recent advancements have witnessed the utilization of animal models in the exploration of the fundamental neural underpinnings of empathic pain. There is substantial evidence implicating multiple brain regions and neural networks in the generation and maintenance of empathic pain. Nevertheless, further elucidation of the neural mechanisms underlying empathic pain is warranted. This review provides a concise overview of prior studies on the neural mechanisms of empathic pain, outlining the pertinent brain regions, neural pathways, synaptic mechanisms, and associated molecules while also delving into future prospects.

Interoceptive awareness mediated the effects of a 15-minute diaphragmatic breathing on empathy for pain: A randomized controlled trial

Although empathy for pain plays an important role in positive interpersonal relationships and encourages engagement in prosocial behavior, it remains largely unknown whether empathy for pain could be effectively altered by psychophysiological techniques. This study aimed to investigate the impact of a single session of diaphragmatic breathing practice on empathy for pain and examine the potential mechanism involving interoceptive awareness. A total of 66 healthy participants were randomly assigned to the intervention group or the control group. The intervention group received a 15-minute diaphragmatic breathing (DB) practice with real-time biofeedback, while the control group was to gaze at a black screen at rest and not engaged in any other activities. Before and after the invention, all participants were instructed to evaluate the intensity and unpleasantness of empathy for pain while watching different pictures with pain or non-pain conditions. The Multidimensional Assessment of Interoceptive Awareness (MAIA) was then administered to measure interoceptive awareness. The results indicated a significant interaction between group and time with regard to empathy for pain and MAIA. The DB group showed a statistically significant decrease in both pain intensity and unpleasantness during the pain picture condition, as well as a noteworthy increase in MAIA scores. The control group did not demonstrate any substantial changes. More importantly, the regulation of attention, a dimension of MAIA, had a significant mediating effect on the impact of diaphragmatic breathing on reported unpleasantness. Diaphragmatic breathing could serve as a simple, convenient, and practical strategy to optimize human empathy for pain that warrants further investigation, which has important implications not only for individuals with impaired empathy for pain but also for the improvement of interoceptive awareness.

Cognitive and affective interaction with somatosensory afference in acupuncture-a specific brain response to compound stimulus

Introduction

Acupuncture is a clinical intervention consisting of multiple stimulus components, including somatosensory stimulation and manipulation of therapeutic context. Existing findings in neuroscience consolidated cognitive modulation to somatosensory afferent process, which could differ from placebo mechanism in brain. Here, we aimed to identify intrinsic process of brain interactions induced by compound stimulus of acupuncture treatment.

Methods

To separately and comprehensively investigate somatosensory afferent and cognitive/affective processes in brain, we implemented a novel experimental protocol of contextual manipulation with somatosensory stimulation (real acupuncture: REAL) and only contextual manipulation (phantom acupuncture: PHNT) for fMRI scan, and conducted independent component (IC)-wise assessment with the concatenated fMRI data.

Results

By our double (experimentally and analytically) dissociation, two ICs (CA1: executive control, CA2: goal-directed sensory process) for cognitive/affective modulation (associated with both REAL and PHNT) and other two ICs (SA1: interoceptive attention and motor-reaction, SA2: somatosensory representation) for somatosensory afference (associated with only REAL) were identified. Moreover, coupling between SA1 and SA2 was associated with a decreased heart rate during stimulation, whereas CA1 was associated with a delayed heart rate decrease post-stimulation. Furthermore, partial correlation network for these components demonstrated a bi-directional interaction between CA1 and SA1/SA2, suggesting the cognitive modulation to somatosensory process. The expectation for the treatment negatively affected CA1 but positively affected SA1 in REAL, whereas the expectation positively affected CA1 in PHNT.

Discussion

These specific cognitive-somatosensory interaction in REAL were differed from vicarious sensation mechanism in PHNT; and might be associated with a characteristic of acupuncture, which induces voluntary attention for interoception. Our findings on brain interactions in acupuncture treatment elucidated the underlying brain mechanisms for compound stimulus of somatosensory afferent and therapeutic contextual manipulation, which might be a specific response to acupuncture.

Predicting response to tVNS in patients with migraine using functional MRI: A voxels-based machine learning analysis

Background

Migraine is a common disorder, affecting many patients. However, for one thing, lacking objective biomarkers, misdiagnosis, and missed diagnosis happen occasionally. For another, though transcutaneous vagus nerve stimulation (tVNS) could alleviate migraine symptoms, the individual difference of tVNS efficacy in migraineurs hamper the clinical application of tVNS. Therefore, it is necessary to identify biomarkers to discriminate migraineurs as well as select patients suitable for tVNS treatment.

Methods

A total of 70 patients diagnosed with migraine without aura (MWoA) and 70 matched healthy controls were recruited to complete fMRI scanning. In study 1, the fractional amplitude of low-frequency fluctuation (fALFF) of each voxel was calculated, and the differences between healthy controls and MWoA were compared. Meaningful voxels were extracted as features for discriminating model construction by a support vector machine. The performance of the discriminating model was assessed by accuracy, sensitivity, and specificity. In addition, a mask of these significant brain regions was generated for further analysis. Then, in study 2, 33 of the 70 patients with MWoA in study 1 receiving real tVNS were included to construct the predicting model in the generated mask. Discriminative features of the discriminating model in study 1 were used to predict the reduction of attack frequency after a 4-week tVNS treatment by support vector regression. A correlation coefficient between predicted value and actual value of the reduction of migraine attack frequency was conducted in 33 patients to assess the performance of predicting model after tVNS treatment. We vislized the distribution of the predictive voxels as well as investigated the association between fALFF change (post-per treatment) of predict weight brain regions and clinical outcomes (frequency of migraine attack) in the real group.

Results

A biomarker containing 3,650 features was identified with an accuracy of 79.3%, sensitivity of 78.6%, and specificity of 80.0% (p < 0.002). The discriminative features were found in the trigeminal cervical complex/rostral ventromedial medulla (TCC/RVM), thalamus, medial prefrontal cortex (mPFC), and temporal gyrus. Then, 70 of 3,650 discriminative features were identified to predict the reduction of attack frequency after tVNS treatment with a correlation coefficient of 0.36 (p = 0.03). The 70 predictive features were involved in TCC/RVM, mPFC, temporal gyrus, middle cingulate cortex (MCC), and insula. The reduction of migraine attack frequency had a positive correlation with right TCC/RVM (r = 0.433, p = 0.021), left MCC (r = 0.451, p = 0.016), and bilateral mPFC (r = 0.416, p = 0.028), and negative with left insula (r = −0.473, p = 0.011) and right superior temporal gyrus/middle temporal gyrus (r = −0.684, p < 0.001), respectively.

Conclusions

By machine learning, the study proposed two potential biomarkers that could discriminate patients with MWoA and predict the efficacy of tVNS in reducing migraine attack frequency. The pivotal features were mainly located in the TCC/RVM, thalamus, mPFC, and temporal gyrus.

Cerebral structural alterations in the patients undergoing postherpetic neuralgia: A VBM-MRI study

This study aimed to investigate the changes in gray matter (GM) volume and density in patients with postherpetic neuralgia (PHN). Using voxel-based morphometry (VBM), the differences in cerebral GM volume and concentration between 25 PHN patients and 25 healthy controls with similar gender ratios, ages, and education were compared. Meanwhile, correlation analysis was performed between the value of GM volume/concentration in the brain areas with discrepancy and the visual analog scale (VAS) score/lesion duration. The global GM volume in PHN patients was lower than that of healthy controls, while the total volume of cerebrospinal fluid in PHN patients was higher than that of healthy controls. In PHN patients, the GM volume decreased in the striatum, cerebellum, precentral gyrus, middle frontal gyrus, parahippocampal gyrus, postcentral gyrus, and so forth; the GM concentration decreased in the striatum, insula, middle and posterior cingulate, and superior temporal gyrus. There was a negative correlation between GM concentration in the right parahippocampal gyrus and the VAS in patients with PHN. In PHN patients, GM volume and density in the brain regions involved in nociceptive sensation, pain perception, and integration decreased significantly. The interaction between chronic pain of PHN and alteration of the cerebral structure may contribute to the occurrence and development of PHN.

The neuroscience of empathy and compassion in pro-social behavior

Research in the scientific literature increasingly demonstrates that empathy consists of multiple dimensions, and that defining empathy as a single encompassing term may be imprecise. Recent calls have been made for increasing empathy as means to increase pro-social behavior. However, contradictory evidence exists that empathy may reduce pro-social behavior. This debate has sparked confusion around what is empathy, along with the value of empathy in promoting pro-social behavior. This paper will examine recent advances in affective neuroscience to better understand the construct of empathy and its relationship to pro-social behavior. Individuals' responses to affective empathy, seeing the suffering of others can result in personal distress or empathic concern, which may then subsequently affect motivation for pro-social behavior. Current research in affective neuroscience suggests that combining compassion interventions in conjunction with both affective and cognitive empathy offers the most optimal likelihood that individuals will engage in pro-social behavior.