ニホンザル一次聴覚野における刺激側の影響について

抄録

The auditory pathways in the mammalian CNS have ipsi- and contralateral components, therefore the auditory cortex receives stimuli from both ears. This work was carried out to observe the effect of the stimulation side in primary auditory cortex of Japanese monkeys. Three Japanese monkeys (Macaca fuscata) weighing 4-7 kg, were anesthetized with ketamine, xylazine and Nitrous oxide. A craniotomy was performed and electrodes were inserted in order to reach the auditory areas. White noise and pure tones were presented by a dynamic earphone. The stimuli had a linear rise time of 10 msec, a plateau of 20 msec and a falling phase of 10 msec. Varnish-coated tungsten microelectrodes were used to record single unit activity, and post stimulus time histograms and tuning curves were constructed. After the recording, the animals were perfused and parvalbumin staining was done to confirm that the units recorded in this study were located in primary auditory cortex (AI and R). The results revealed that the side of unilateral stimulus (ipsilateral or contralateral) did not influence the best frequency of the AI and R neurons. As there are several cross-overs in the auditory system, the each hemisphere receives the hearing information from both ears. The results of this study are compatible with the hypothesis that there are strong connections between the zones of different areas with the same best-frequency, and the auditory center has a simple systems to process various and complicated auditory informations.