Hot sauce study finds asymmetric placebo effect may offer insight into pain perception

Humans’ expectations of a pleasant sensation asymmetrically shape neural responses and subjective experiences to hot sauce, according to a study published October 8 in the open access journal. Biology PLOS by Yi Luo of East China Normal University, Kenneth Kishida of Wake Forest School of Medicine, USA, and colleagues.

Expectations shape our perception and profoundly influence how we interpret the world. Positive expectations about sensory stimuli can alleviate distress and reduce pain through the so-called placebo effect, while negative expectations can increase anxiety and exacerbate pain. In the new study, Luo, Kishida and their colleagues investigated the impact of the hedonic aspect of expectations on subjective experiences.

Specifically, the researchers measured neurobehavioral responses to the taste of hot sauce in individuals with a wide range of taste preferences.

A total of 47 participants completed the tasks while undergoing functional magnetic resonance imaging. The researchers identified participants who liked spicy flavors versus those who strongly disliked them and provided contextual clues about how hot the sauce was to taste.

In this way, they were able to dissociate the effects of positive and negative expectations from sensory stimuli (i.e. visual and taste stimuli), which were the same for all participants.

The results showed that positive expectations lead to modulations in the intensity of subjective experience. These modulations were accompanied by increased activity in brain regions previously linked to pleasure, information integration, and the placebo effect, including the anterior insula, dorsolateral prefrontal cortex, and anterior cingulate cortex. dorsal.

In contrast, negative expectations decreased hedonic experience and increased neural activity in the pain neurological signature network.

Taken together, these findings demonstrate that hedonic aspects of a person’s expectations asymmetrically shape how the brain processes sensory input and associated behavioral reports of subjective experiences of intensity, pleasure, and pain. The results suggest a dissociable impact of hedonic information.

While positive expectancies facilitate higher-level information integration and reward processing, negative expectancies promote lower-level processes related to pain and emotion. According to the authors, this study demonstrates the powerful role of hedonic expectations in shaping subjective reality and suggests potential avenues for therapeutic and consumer interventions targeting the neural processes induced by expectations.

The authors add: “Our study highlights how hedonic expectations shape subjective experiences and neural responses, providing new insights into the mechanisms behind pain perception. »