A cortical basis for perception of internal gut sensations
Interoception, the sensing of internal bodily signals, is essential for brain-body interactions and shapes emotion, cognition, and behavior1-5. Subconscious internal signals, including heartbeats or stomach fullness, can rise to conscious awareness, and this process can improve with practice, as seen in meditation, mindful eating, or toilet training in early infancy. Conversely, disrupted interoception is emerging as a common deficit in diverse psychiatric disorders1,3,6,7. Nevertheless, we still lack a fundamental understanding of the neurobiological basis of perception and conscious reporting of internal sensations. Here, we combine genetic and ultra-sensitive optogenetic tools in mice to establish a quantitative framework for studying internal perception. We developed a behavioral task in which mice report detecting non-invasive optogenetic activation of gut mechanosensory neurons, establishing "interoceptive psychophysics". We combine this approach with cellular-resolution imaging and manipulations to reveal the neuronal basis for perception of these internal gut sensations in the interoceptive insular cortex. While representations of sensory stimuli were consistently observed in insular cortex across different tasks, we found that perceptual reports were only encoded during a more difficult psychophysics task, but not during basic detection. Accordingly, manipulation of insular cortex activity affected behavioral reports only in the psychophysics task. These findings reveal a neural basis for perception of internal gut sensations and provide a blueprint for future quantitative exploration of other interoceptive modalities.