Neural representation of hedonic valence during narrative listening
Hedonic valence, the intrinsic pleasantness or unpleasantness of an experience, is fundamental to human psychological functioning. Yet, how valence is represented in the brain remains an open question. Functional MRI studies have demonstrated that the brain encodes both positive and negative valence, but this evidence largely stems from experiments using simplified, controlled stimuli, such as images, sounds, or words. As a result, it remains unclear how valence is processed during rich, naturalistic experiences that more closely reflect real life. In addition, most studies adopt a single statistical model, raising concerns about the robustness of their findings. This study used a formal voxel-wise Bayesian model selection approach to test alternative statistical models supporting Bipolarity, Valence-General, and Bivalence hypotheses to identify the most optimal model of valence representation during narrative listening. Our results provide evidence for the Bipolar model. We identified distributed brain regions that selectively encode valence as a bipolar continuum (negative to positive) during narrative comprehension, including classical emotion-related hubs such as ventromedial prefrontal cortex, as well as regions not traditionally associated with emotion processing, such as inferior occipital cortex, supramarginal cortex, inferior frontal cortex, and middle cingulate. Regions selectively encoding arousal and those broadly responsive to both valence and arousal were also identified. These findings highlight the importance of using formal model comparison and naturalistic paradigms in affective neuroscience, advancing our understanding of how valence is represented in the brain during real-world experiences.