The role of insular cortex in reward learning

感官信息可以作为识别对象的线索，包括奖励对象和厌恶对象。但是，需要一个学习的过程来使用这些信息作为线索。感觉信息与奖励结果之间的联系会改变神经回路，并可能有助于改变感觉线索的价值。 虽然许多大脑区域都涉及进食行为，但人们对回路中哪些神经元介导识别可食用食物的能力知之甚少。岛叶皮层是提供效价信息的一个重要区域。岛叶皮层是整合传入的感觉信息（包括躯体感觉和内脏信息）的大脑区域，并且也被称为味觉皮层。此外，最近的研究表明，通过整合来自内脏线索和奖励对象的感觉成分的信息，岛叶皮层神经元可以强大地调节食欲行为。因此，笔者推测，在线索-奖赏联想学习训练中，岛叶皮层也会形成和完善参与线索-奖赏学习的神经回路。 本研究的主要目的是证实在线索-奖赏联想学习训练中，岛叶皮层神经元的突触输入是否会增强。为了获得关于岛叶皮层神经元连接的更精确的解剖学信息，通过使用称为荧光金的示踪剂逆行标记神经元来观察传入到岛叶皮层的传入输入。巴甫洛夫条件反射任务被用作线索奖励学习的模型行为。小鼠在一周内学会了感觉提示和食物奖励之间的联系。为了证实岛叶皮层参与了这一行为，进行了药理学实验。采用电生理学方法测量传入岛叶皮层神经元的突触传入。

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.