Convergence of taste and visceral input in the insulr cortex in rats

在大鼠中，现在已经认识到，岛叶皮层的前部和后部分别被认为是味觉和内脏感觉区。然而，岛叶皮层这两个区域的功能作用仍然无法解释。此外，味觉和内脏区域之间可能存在联系。本研究旨在观察大鼠岛叶皮层神经元对味觉、内脏和伤害性刺激的反应特性。用电生理方法记录岛叶皮层神经元的单个单位活动。结果如下：（1）岛叶皮层神经元接受来自味觉神经的会聚性输入，包括鼓索、舌咽神经舌扁桃体分支、舌咽神经咽分支和上级喉神经。岛叶皮层神经元对舌咽神经舌扁桃体分支、舌咽神经咽分支和上级喉神经的刺激均有反应;（2）舌后区和咽喉区的味觉刺激引起的岛叶皮层味觉敏感神经元大多数也对内脏感觉（包括压力感受器和化学感受器）产生反应，（3）在味觉区和内脏感觉区之间或岛叶皮层的中间区记录到多模式反应的神经元。这些结果表明，岛叶皮层的中间区域接受来自各种感觉器官的会聚输入，可能在情绪系统中发挥一定的作用。

In rats, it has now been recognized that the anterior and posterior of the insular cortex are considered as taste and visceral sensory areas, respectively. However, the functional role of these two areas of the insular cortex is still unexplained. Furthermore, there may be a link between the taste and visceral areas. This study is an examination of the response properties in the neurons of the rat insular cortex to gustatory, visceral, and nociceptive stimuli. The single unit activity in the neurons of the insular cortex was recorded by using electrophysiological methods. The results are as follows: (1) The neurons in the insular cortex receive convergent inputs from taste nerves, including the chorda tympani, the lingual-tonsilar branch of the glossopharyngeal nerve, the pharyngeal branch of the glossopharyngeal nerve, and the superior laryngeal nerve. Most neurons in the insular cortex responded to all three taste-nerve stimuli, including the lingual-tonsilar branch of the glossopharyngeal nerve, the pharyngeal branch of the glossopharyngeal nerve, and the superior laryngeal nerve; (2) Most of the taste-sensitive neurons to gustatory stimulation of the posterior tongue and pharyngolaryngeal region in the insular cortex responded also to the visceral senses, including baro- and chemoreceptor, and to the nociceptive stimulation of the tail pinch; and (3) Those neurons showing multimodal response were recorded between the taste and visceral sensory areas or in the intermediate region of the insular cortex. These results suggest that the intermediate region of the insular cortex receiving convergent inputs from various sensory organs may have some role in the emotional system.