Subjects: Psychology >> Cognitive Psychology submitted time 2023-02-14
Abstract：
Under the influence of the novel coronavirus epidemic, some negative social events, such as separation of family or friends and home isolation have increased. These events can cause negative emotion experiences similar to physical pain, thus they are called social pain. Placebo effect refers to the positive response to the inert treatment with no specific therapeutic properties, which has been shown to be one of the effective ways to alleviate social pain. Studies have shown that the dorsolateral prefrontal cortex (DLPFC) plays a key role in placebo effect. Therefore, this study aimed to explore whether activating DLPFC by using transcranial magnetic stimulation (TMS) could improve the ability of placebo effects to regulate social pain. Besides, we also combined neuroimaging and neuromodulation techniques to provide bidirectional evidence for the role of the DLPFC on placebo effects. We recruited a total of 100 participants to finish the task of negative emotional rating of the social exclusion images. Among them, 50 participants were stimulated by TMS at the right DLPFC (rDLPFC), while the others were assigned to the sham group. This study contained two independent variables. The between-subject variable was TMS group (rDLPFC-activated group or sham group) and the within-subject variable was placebo type (no-placebo and placebo). All participants received nasal spray in two blocks. In the no-placebo condition, participants were instructed that they would receive a saline nasal spray which helped to improve physiological readings; in placebo block, participants were told to administrate an intranasal fluoxetine spray (saline nasal spray in fact) that could reduce unpleasantness within 10 minutes. To strengthen the expectation of intranasal fluoxetine, participants viewed a professional introduction to fluoxetine’s clinical and academic usage including downregulating negative emotion, such as fear, anxiety, and disgust. Participants who received the placebo block first would be reminded that fluoxetine’s effect was over before the next block to reduce the carry-over for the following block. Self-reported negative emotional and electroencephalogram data were recorded. There was a significant two-way interaction of TMS group and placebo type. Results showed that compared with the sham group, participants in the rDLPFC-activated group reported less negative emotional feeling and had a lower amplitude of the late positive potential (LPP) in placebo condition, a component that reflects the emotional intensity, suggesting that activating rDLPFC can improve the ability of placebo effect to regulate social pain. The above finding suggested that activating DLPFC can improve the placebo effect of regulating negative emotion. Moreover, this study is the first attempt to investigate the enhancement of placebo effects by using TMS on emotion regulation. The findings not only support the critical role of DLPFC on placebo effect using neuroimaging and neuromodulation techniques, but also provide a potential brain target for treating emotional regulation deficits in patients with psychiatric disorders.
Peer Review Status:
Awaiting Review
Subjects: Psychology >> Cognitive Psychology submitted time 2022-08-02
Abstract： Emotion regulation is crucial to mental health and social life. Traditional view conceived emotion regulation as a deliberative process. However, there is growing evidence that emotion regulation can implement at an implicit level without or with limited involvement of the lateral prefrontal cortex (LPFC) that is responsible for cognitive control. Unlike explicit emotion regulation, we have few knowledge on the neural mechanisms underlying implicit emotion regulation. Here, we investigated the effect of excitatory the ventromedial prefrontal cortex (vmPFC) using transcranial direct current stimulation (tDCS) to provide causal evidence for the key role of the vmPFC in implicit emotion regulation. This study had a mixed design, with group (anodal vs. sham) as the between-subject factor and priming type (reappraisal vs. baseline) as the within-subject factor. A total of 80 participants were recruited and randomly assigned to the anodal group and the sham tDCS group. The task was divided into two blocks, i.e., the implicit reappraisal block and the baseline block. The order of the two blocks was counterbalanced within the participants in each group. At the beginning of each block, participants were required to complete a tDCS session (1.5 mA; 10 min for the active group and 1 min for the sham group). The anodal electrode was placed in the middle of Fz and Fpz and the ground electrode was placed under the chin). Then, participants completed six sessions of sentence unscramble task (10 trials per session) to prime the emotion regulation goal. Each session of the sentence unscramble task was followed by a picture viewing task (5 trials) to evoke negative emotions. The self-reported emotion rating and EEG signals were recorded during the picture viewing task. Half an hour after the end of the picture viewing task, participants were asked to rate the valence (1 = very unpleasant; 9 = very pleasant) of all viewed images in the picture viewing task. The results showed that the experimental group (n = 40) reported lower negative emotional experience and showed lower LPP amplitudes (measured as the average amplitude of Pz P3, P4, CP1, CP2) when the vmPFC was activated in the cognitive reappraisal block compared to the control group (n = 40), indicating that excitatory vmPFC could effectively facilitate the ability of implicit emotion regulation. Furthermore, we also found that excitatory vmPFC can reduce the P1 amplitude (measured as the average amplitude of O1, O2) under both baseline and reappraisal conditions. The above results indicated that activating the vmPFC could not only facilitate implicit emotion regulation but also reduce early attention distribution to negative stimuli. This study is the first attempt to use the tDCS technique to investigate priming-induced implicit emotion regulation. The results directly reveal the causal relationship between the vmPFC and implicit cognitive reappraisal, suggesting this brain region as a potential target of neural modulation to enhance the ability of implicit emotion regulation in clinical populations.
Peer Review Status:Awaiting Review
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