Opioid and orexin hedonic hotspots in rat orbitofrontal cortex and insula

Orbitofrontal cortex, insula, and related cortical regions are implicated in pleasure and motivation. However, determining whether cortical sites help cause hedonic reactions or instead merely encode signals generated elsewhere to facilitate other functions such as cognition remains unresolved. By mapping hedonic effects of individual drug microinjections, we generate detailed anatomical maps for potential gain-of-function affective sites in rat limbic cortex. Here, we show that opioid or orexin stimulations in orbitofrontal cortex and insula causally enhance hedonic "liking" reactions to sweetness and find a third cortical site where the same neurochemical stimulations reduce positive hedonic impact. For comparison, we also map overlapping but separable regions where stimulations increase the motivation to eat.