Mapping a Novel Hedonic Hotspot in Insular Cortex

Abstract

Insular cortex has been implicated in a wide array of functions, including integrating multiple sensory modalities, coding disgust for unpleasant foods, and processing reward and motivation. Specifically, anterior insula appears to be involved in mediating disgust while posterior insula may produce positive affect and code for palatable food stimuli. The current known regional functions within insular cortex support the prediction of a hedonic hotspot and coldspot in anatomically localized areas. To determine whether such pleasure/displeasuregenerating zones actually exist in the region, anterior and posterior regions within insular cortex were selectively stimulated with DAMGO (mu-opioid agonist) or orexin-A, a peptide that is only produced in lateral hypothalamus. Posterior insular stimulation with either agonist amplified “liking” reactions to sucrose by three-fold, but failed to enhance intake of palatable M&M chocolate candies. In contrast, preliminary results from anterior insula stimulation with DAMGO or orexin shows suppressed “liking” of sucrose and no change in consumption of M&Ms. Taken together, these results support the discovery of a hedonic hotspot in posterior insula, and a potential hedonic coldspot in anterior insula. These results provide the first direct evidence for any cortical region amplifying or suppressing pleasure, and have important evolutionary implications on social and economic rewards in humans.