Cooperative acoustic and auditory study on tree shrew

点击翻译按钮获取中文摘要

The purpose of this project is to make a catalog of the vocalization and to characterize the neurons of inferior colliculus and auditory cortex in the tree shrew (Tupaia belangeri chinensis), which is specific in the evolutionary point of view as primitive primates. A partner, Dr.Xinde Sun, has studied on the auditory system of the animal collected in the southern China, to which we joined for collaboration.The vocalization was analyzed first. One of the investigators visited Shanghai and recorded the vocalization in the sound proof room. The vocalization was recorded from female alone, male alone or from male and female in the analog tape and digitized by computer. The three kinds of vocalization were recognized, one of which was emiteed most often. The sound is composed of 6 to 7 syllables and emitted seriously, which is very specific to the animal. The digitized files were analyzed furthermore in Hong Kong, into which Kamada participated. Totally 500 sounds were analyzed and statistically divided based upon the durations, frequencies and frequency change with time. The result suggested there are two groups in the sounds, correspondingly to female and male. The fact is examined again this year. But there were limitations in laboratory condition to make clear that there are no more vocalizations other than 3 compared to natural condition.The sexual dimorphism was examined further in our laboratory with Dr.Sun invited here using KAY sonagraph. The careful analysis indicated the dimorphism in frequency and frequency change.Neurophysiological experiments were tried in inferior colliculus. Neurons were examined in basic properties and FM sensitivity. There was a difficulty in accessing the electrode to inferior colliculus because of overlapped superior colliculus on it. The basic responsibility and FM sensitive were similar to other mammals. Then we examined the auditory cortex.