Abstract: As basic emotions, fear and disgust are negative emotions that are related to threats and make people feel strongly unpleasant. They are of great importance to human survival and adaptation. Moderate fear and disgust are conducive to the individual's awareness of danger and rapid defensive responses, but excessive fear and disgust will affect the individual's daily functioning and may even develop into post-traumatic stress disorder, obsessive-compulsive disorder, phobia, and other anxiety disorders. Previous studies have shown that excessive fear is the core mechanism of anxiety disorders, ignoring the role of disgust in it. In recent years, with the emergence of the ineffectiveness of exposure therapy for certain anxiety disorders and the disclosure of the close relationship between disgust and anxiety disorders, researchers began to explore the mechanisms underlying anxiety disorders from a new perspective. That is, disgust is also an important pathogenic factor of anxiety disorder, and fear and disgust should be combined to explain the pathogenesis of anxiety disorder.
Fear and disgust are the main emotions of anxiety disorders, and analyzing the characteristics of fear and disgust from the perspective of conditioned learning is expected to provide an important basis for related clinical treatment. Pavlovian conditioning is a classic paradigm for fear and disgust learning. A differential conditioning paradigm is often used in fear learning and disgust learning: a neutral stimulus(CS+) is repeatedly paired with an unconditional stimulus (US) that can cause aversion, and another neutral stimulus (CS-) never paired with unconditioned stimulus(US), as a result, only presenting a neutral stimulus (CS+) will cause aversive responses. Fear and disgust conditioning not only simulates the acquisition and extinction of fear and disgust, improving our theoretical understanding of the functional properties of fear and disgust, but also has implications for the prevention and targeted treatment of fear and disgust diseases.
Therefore, this article analyzes the characteristics of fear and disgust from the perspective of conditional learning, and summarizes the differences between fear learning and disgust learning. This article has three aims. First, the article discusses the relations among fear, disgust, and related anxiety disorders, and distinguishes the dominance of the two emotions. Secondly, from the perspective of conditioned learning, it compares the behavioral and neural mechanisms of fear and disgust. An in-depth analysis of extinction differences was carried out. Finally, from the insufficiency of research on disgust conditioning learning, we discussed directions for future studies. That is, future research can continue to explore the mechanisms underlying the disgust learning from generalization, extinction intervention, etc., and try to use adolescents and clinical patients as target groups. In sum, the emotional dominance of several different subtypes of anxiety disorder is distinguished and summarized, which provides an important theoretical basis for the screening of clinical anxiety disorder treatment targets; The differences between fear and disgust conditioning in subjective feelings, physiological response and functional brain areas indicate that exposure therapy is indeed an effective treatment for fear-led anxiety disorders, but cognitive intervention may be preferred for disgust-led disorders.

Key words: disgust, fear, anxiety disorders, classical conditioning

摘要： 过度的恐惧及厌恶是焦虑障碍的核心特征之一,从条件学习视角探析恐惧与厌恶的特性,有望为相关临床治疗提供重要依据。首先从面部表情、心率、认知及功能脑区层面论述了恐惧、厌恶与焦虑相关疾病的情绪主导性关系。其次,从条件学习视角对比恐惧和厌恶的行为与神经机制差异,发现相对于习得的恐惧,厌恶更难以消除;两者的条件学习既会共同激活dACC、OFC和NAcc等参与联结意识发展和效价评估的脑区,也会激活各自特异的功能脑区,如杏仁核等在恐惧学习中具有重要地位,脑岛在厌恶学习中具有重要地位。最后,从厌恶条件学习研究的不足性,讨论了未来研究可以从泛化、消退干预等方向继续探究。

关键词: 厌恶, 恐惧, 焦虑障碍, 经典条件作用