认知与发展心理学研究室知识库

A 型肉毒毒素（简称肉毒素）可引起可逆的局部肌肉麻痹，注射于特定面部肌肉可影响个体的情绪体验，还会干扰个体对情绪性材料（阈上呈现的面部表情、语言文字和视频）中情绪信息的加工，这些现象可能与肉毒素注射对杏仁核、奖赏系统的功能，以及部分与运动和认知加工相关的皮层功能的影响有关。但是，目前尚不清楚肉毒素注射是否会影响个体对阈下面部表情的加工。本研究通过采用表情刺激阈下呈现的实验范式，考察肉毒素注射对阈下面部表情加工的影响，并在前人研究基础上，考察肉毒素注射对主观情绪体验和阈上表情识别的影响。

本研究采用纵向对照组实验设计，37名25至48岁健康被试在4个月内按实验组肉毒素注射的不同阶段进行3次同样的一组阈下表情识别实验任务。为了同时追踪被试的情绪状态，采用情绪自评量表测量被试在不同阶段的主观情绪体验。同时，为了与阈下面部表情加工进行对比，被试也分别完成3次阈上表情识别任务。其中实验组被试19名，在前测后接受肉毒素注射，药物起效后（药物注射后大约7至14天）进行中测，肌肉恢复后（药物注射后大约3至4个月）进行后测；对照组被试18名，不进行注射，三次测试的时间间隔与实验组的平均时间间隔一致。

前中后测的阈下面部表情加工任务采用连续闪烁抑制和视觉掩蔽的阈下情绪启动实验范式，要求被试对阈下呈现的表情图片后出现的中性目标表情进行情绪效价强度的主观评分（情感错误归因程序范式），或者对随后出现的积极或消极表情目标图片进行正负性的快速分类判断（评价启动任务范式），考察肉毒素 注射对阈下面部表情的情绪启动效应的影响。采用焦虑自评量表和抑郁自评量表 对被试在前中后测时的抑郁和焦虑情绪进行测量，考察肉毒素注射对健康个体主观情绪体验的影响。在前中后测也采用局部面部表情和完整面部表情的阈上识别任务，考察肉毒素注射对阈上面部表情加工的影响，与阈下表情加工任务的结果 模式进行对比。

前中后测的结果如下。首先，在视觉掩蔽范式中，肉毒素注射干扰了情感错误归因程序中的阈下情绪启动效应，而对评价启动任务结果无显著影响。其次，在连续闪烁抑制范式中，未发现显著的阈下情绪启动效应，也未发现肉毒素注射对该效应的显著影响。最后，主观情绪体验的评分表明，实验组与对照组之间，以及各组前中后测之间的抑郁和焦虑情绪状态都无显著差异；阈上表情加工任务发现，肉毒素注射干扰了实验组被试对阈上完整表情的识别，尤其是对愤怒表情的识别，对其他条件下的阈上表情识别无显著影响。

上述发现表明，首先，肉毒素注射可以影响阈下水平的面部反馈效应，即肉毒素注射引起的肌肉麻痹导致原本由启动表情激活的面部反馈信息受阻，干扰被试对目标中性表情的情感错误归因。其次，肉毒素注射对情感错误归因程序与评价启动任务的影响不同，佐证了两者的潜在机制差异：情感错误归因程序的阈下启动效应基于个体的生理活动，肉毒素注射影响较大；而评价启动任务与对情绪性刺激的评价性反应有关，启动刺激引起的阈下面部反馈效应被习得反应和已有知识经验掩盖。最后，肉毒素注射眉间通过干扰被试对阈上消极表情的细分，使得愤怒表情与其他表情混淆，影响个体对阈上完整表情的识别。总体而言，阈上表情加工任务作为对前人研究的验证和补充，为阈下研究结果的归因提供了锚点；通过阈下任务进一步排除了概念水平加工的作用，发现无意识水平下的肌肉活动变化可直接影响个体的表情加工；但这一肌肉活动变化对健康个体情绪体验并没有显著影响。

本研究在前人研究基础上初步探索了阈下意识水平下肉毒素注射对面部表情加工的影响，尽可能减少了概念水平加工和已有知识经验的影响，进一步证实了肉毒素注射引起的肌肉麻痹和情绪加工变化的因果关系，对于面部反馈效应的探究和肉毒素的实际使用有着重要的理论意义和应用价值。

Botulinum toxin type A (BTX) induces a reversible muscle paralysis at the injection site. There is evidence that BTX injection in specific facial muscles affects emotional experience and the processing of emotional stimuli (e.g., supraliminal facial expressions, emotional language, and videos). The mechanisms behind these phenomena could be that BTX injection can affect the neural basis of emotional processing, including the function of amygdala, reward system and certain cortex related to motor and cognition. However, it’s still unclear whether BTX injection has any effect on subliminal facial expression processing.

The current study used the subliminal paradigms to investigate the effect of BTX injection on subliminal facial expression processing. Based on the previous researches, the effects of botulinum toxin injection on subjective emotional experience and supraliminal expression recognition were also investigated. The current study used a longitudinal controlled design. The subliminal experimental tasks were conducted on 37 normal subjects aged 25 to 48 and were repeated 3 times during 4 months according to different stages of BTX injection. Self-rating emotional scales were also used to measure their subjective emotional experience at different stages. Supraliminal tasks were also conducted to compare with the subliminal tasks. 19 subjects accomplished the pre-, mid- and post-test, right before receiving BTX injection, after BTX taking effect (7 to 14 days after injection) and after BTX losing efficacy (3 to 4 months after injection), respectively. 18 subjects in the control group didn’t receive any injection and the time interval between 3 stages was in accordant with the average time interval of the experimental group.

Using the continuous flash suppression (CFS) paradigm and the visual mask (VM) paradigm in the pre-, mid-, and post-test, the current research investigated the impact of BTX injection on subliminal affective priming effect. Subjects were required to rate the valence of the neutral expressions (affective misattribution procedure, AMP), or to classify the valence of the positive or negative expressions as quickly as possible (evaluative priming task, EPT) shown after the subliminal prime expressions. To investigate the effect of BTX injection on subjective emotional experience, this research also used the self-rating anxiety scale (SAS) and the self-rating depression scale (SDS) to measure the emotional state of the participants through 3 stages. To compare with the subliminal expression processing, the supraliminal facial expression recognition tasks were also conducted to investigate the effect of BTX injection on partial and complete facial expression recognition.

The results are as follows. First, results showed that BTX injection can interfere with subliminal affective priming effect in the AMP under VM, but no such effect was found in the EPT. Second, no subliminal affective priming effect under CFS was found, nor the impact of BTX injection on it. Last, the self-rating scales’ results showed no significant difference between two groups or among 3 stages; the supraliminal tasks’ results indicated that BTX injection can interfere with recognition of the complete facial expressions, especially anger, but no significance was found under other conditions.

The findings above indicate that, first, BTX injection can affect the facial feedback effect at the subliminal level. That is, the muscle paralysis caused by BTX injection blocked the facial feedback information induced by the priming facial expressions, and interfered with the affective misattribution occurred to the neutral stimuli. Second, the different effect of BTX injection on AMP and EPT is consistent with the different potential mechanisms of the two tasks: the subliminal priming effect of AMP is based on physiological activities, so BTX injection has larger effect on it; while the priming effect of EPT is related to the evaluative response to the emotional stimuli, so the potential facial feedback is covered by the subjects’ existing knowledge or experience and learned response. Finally, BTX injection may interfere with the subdivision of negative expressions, causing anger to be confused with other expressions, thus affect the recognition of the supraliminal complete facial expression. Overall, as a validation and supplements to the previous researches, the supraliminal expression recognition tasks provide an anchor point for the attribution of subliminal research findings. Through subliminal tasks, it was further clarified that the change of muscle activity could affect the processing of facial expressions directly without conceptual processing. However, this change of muscle activity could not affect the normal subjects’ subjective emotional experience significantly.

This study preliminarily explored the effect of BTX injection on subliminal facial expression processing, with the minimized influence of conceptual processing and individual knowledge or experience. Thus, it provided further evidence for the causal relationship between muscle paralysis caused by BTX injection and emotional processing changes, which has important theoretical significance and practical value for the investigation of the facial feedback effect and the clinical use of BTX.