|Budget Amount *help
¥2,800,000 (Direct Cost: ¥2,800,000)
Fiscal Year 1999: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1998: ¥2,300,000 (Direct Cost: ¥2,300,000)
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.