关键词: 情绪调节, 内隐自动化情绪调节, 条件化安慰剂效应, 背外侧前额叶

Abstract: Placebo effects have been conceptualized as an automatic emotion regulation strategy that requires limited engagement of frontal regions and can operate under constrained cognitive resources. As such, they may represent a low-demand regulatory pathway, particularly beneficial for individuals with compromised prefrontal functioning. However, prior research has primarily focused on expectancy-based placebo effects, whereas the role of classical conditioning—operating in the absence of explicit expectations or intentional regulatory goals—remains largely unexplored, especially in the domain of emotion regulation. Although the dorsolateral prefrontal cortex (DLPFC) has been shown to play a causal role in expectancy-driven placebo effects, its involvement in conditioned placebo effects remains unclear. The present study examined whether classically conditioned placebo effects can attenuate negative emotions and whether the DLPFC plays a causal role in this process.
Seventy healthy participants completed a classical conditioning paradigm. Before the conditioning phase, repetitive transcranial magnetic stimulation was applied either to the right DLPFC or to a control site at the vertex. During both the conditioning and test phases, subjective ratings of negative emotion and pupil diameter were recorded as indices of emotional arousal and cognitive resource allocation. The results showed that, during conditioning, participants in the DLPFC group exhibited significantly greater pupil dilation in response to positive cues than those in the control group, indicating enhanced cognitive resource engagement. Moreover, participants in the DLPFC group reported lower negative emotion ratings and showed reduced pupil responses to images paired with positive cues, suggesting the formation of more positive emotional representations. During the test phase, both groups showed significant placebo and nocebo effects. Critically, however, the placebo effect was significantly stronger in the DLPFC group, as reflected in lower negative emotion ratings and smaller pupil responses following positive cues. Mediation analyses further revealed that DLPFC activation did not directly enhance the placebo effect. Instead, it exerted an indirect effect by increasing cognitive resource allocation to positive cues during conditioning and by amplifying representational differences between cue-emotion associations.
The present study provides causal evidence that the DLPFC contributes to the formation of classically conditioned placebo effects in negative emotion regulation. These findings extend placebo research beyond expectancy-based mechanisms and identify conditioning as a viable low-cognitive-load pathway for emotion regulation, with important theoretical and potential clinical implications for individuals with limited executive resources.

Key words: emotion regulation, implicit-automatic emotion regulation, conditioning placebo effect, dorsolateral prefrontal cortex