How emotions are reflected in gastric myoelectrical activity: is it a reliable marker?

Emotions have a basic impact on cognition, behavior, and general well-being in humans. Numerous physiological techniques have been used to study them, however compared to respiratory, cardiac, electrodermal, and facial myoelectrical activity, less focus has been placed on gastric myoelectrical activity during emotional states. Electrogastrography (EGG) has gained popularity recently for examining the connection between gastrointestinal electrical activity and emotions. The aim of this narrative review is to provide a comprehensive understanding of the link between gastric myoelectrical activity and emotions, highlighting the potential of EGG as a tool for studying the physiological underpinnings of emotions. In general, the effect of emotional states on gastric activity has not been studied sufficiently. A scarce amount of research is described both within dimensional and discrete approaches to emotions. In addition, there is no consensus on the standardized protocol of analysis. The results are contradictory and show that gastric activity may be related to valence, arousal or discrete emotional states. In general, different emotional states appear to decrease normogastria reflecting complex, non-linear autonomic and myogenic shifts rather than a simple branch-specific reaction. Integrated EGG and other autonomic measures can further improve understanding of the physiological foundations of emotion. Nevertheless, current advancements suggest that gastric myoelectrical activity holds significant potential to serve as a distinctive indicator of affective states, whether mapped onto dimensional axes (valence and arousal) or encapsulated within discrete emotional categories such as sadness or disgust.