The role of insular cortex in reward learning

感官信息可以作为识别物体的线索，无论是奖励物体还是厌恶物体。然而，学习过程需要使用这些信息作为线索。感觉信息与奖励结果之间的关联会改变神经回路，并可能导致感觉线索价值的改变。尽管大脑的许多区域都与进食行为有关，但回路中哪些神经元调节识别可食用食物的能力却鲜为人知。一个可能提供价信息的重要区域是岛叶皮层。岛叶皮层是大脑的一个区域，它整合传入的感觉信息，包括体感和内脏信息，也被称为味觉皮层。此外，最近的研究结果表明，通过整合来自内脏线索和奖励物体的感觉成分的信息，岛皮质神经元可以有效地调节食欲行为。因此，我假设在线索奖励联想学习训练过程中，涉及线索奖励学习的神经回路也会在岛叶皮层形成和完善。

Sensory information can be used as clue for identifying objects, both rewarding objects and aversive objects. However, learning process would be required to use that information as clue. The association between sensory information and rewarding outcome would modify neural circuits and probably contribute to change value of the sensory cue. Although many brain areas are involving eating behavior, it is poorly known which neurons in the circuit mediate the ability to identify edible foods. One important region that may supply valence information is the insular cortex. The insular cortex is a brain region that integrates incoming sensory information including somatosensory and visceral information and is also known as the taste cortex. Furthermore, recent findings suggest that through the integration of information coming from visceral cues and sensory component of rewarding objects, insular cortex neurons can powerfully modulate appetitive behaviors. Therefore, I hypothesize that neural circuit that involve in cue-reward learning will also be made and refined in the insular cortex during cue-reward association learning training. Major purpose of this research is to confirm whether synaptic inputs into insular cortex neurons would be potentiated during cue-reward association learning training. To get more precise anatomical information about neuronal connection in the insular cortex, observation of afferent inputs into insular cortex by labeling neurons retrogradely using tracer called Fluorogold was performed. Pavlovian conditioning task was used as a model behavior of cue-reward learning. Mice learned association between sensory cue and food reward within one week. To confirm insular cortex is involved to this behavior, pharmacological experiments were performed. Electrophysiological approach was used to measure synaptic inputs into insular cortex neurons.