The role of insular cortex in reward learning

感官信息可以作为识别对象的线索，既有奖励对象，也有厌恶对象。然而，需要学习过程才能使用这些信息作为线索。感觉信息和奖励结果之间的关联将改变神经回路，并可能有助于改变感觉线索的价值。虽然大脑的许多区域都与进食行为有关，但人们对该回路中哪些神经元参与识别可食用食物的能力知之甚少。可能提供价态信息的一个重要区域是岛叶皮质。岛叶皮质是一个大脑区域，它整合了传入的感觉信息，包括躯体感觉和内脏信息，也被称为味觉皮质。此外，最近的发现表明，通过整合来自内脏线索的信息和奖励对象的感觉成分，岛叶皮质神经元可以有力地调节食欲行为。因此，我推测，在线索-奖赏联想学习训练中，岛叶皮质也会建立和完善与线索-奖赏学习有关的神经回路。 本研究的主要目的是证实在线索-奖赏联想学习训练过程中，岛叶皮质神经元的突触输入是否会得到增强。为了获得更准确的岛叶皮质神经元连接的解剖学信息，用荧光金标记的示踪剂逆行标记神经元，观察了传入岛叶皮质的信息。巴甫洛夫条件反射任务被用作线索奖赏学习的模型行为。老鼠在一周内学会了感觉线索和食物奖励之间的联系。为了证实岛叶皮质与这种行为有关，进行了药理学实验。用电生理学方法测量岛叶皮质神经元的突触输入。

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.