白眉　（Emberiza　tristrami　Swinhoe）听觉中继核团上橄榄核的神经联系──HRP法研究

NEURAL CONNECTIONS OF AN AUDITORY RELAY NUCLEUS, NUCLEUS OLIVARIS SUPERIOR IN EMBERIZA TRISTRAMI SWINHOE ──AN HRP METHOD STUDY

采用ＨＲＰ顺逆行示踪技术对白眉 延脑听觉中继核团上橄榄核的纤维联系进行了研究。结果表明：上橄榄核接受双侧角状核的传入投射，并发出纤维上行投射至双侧外侧丘系核和中脑背外侧核。上橄榄核与角状核的联系以同侧为主，与外侧丘系核的联系以对侧为主。上橄榄核还发出纤维下行投射至巨细胞核。双侧上橄榄核之间还存在着交叉投射。

Auditory central pathways in birds have been studied by many authors. However, the neural connections of some auditory nuclei remain unclear. In the present study. HRP tracing method was used to investigate the afferents and efferents of an auditory relay nucleus, nucleus olivaris superior(OS) in Emberiza tristrami Swinhoe.Thirty animals received unilateral injections of HRP. Nine of them had misplaced HRP injections in the nearby structures of OS and were used to serve as controls in determining the neural connections of OS. In twenty-one animals with HRP injection into OS, anterogradely labelled fibers and terminals were observed in ipsilateral nucleus magnocellularis (NM),contralateral OS, the nuclei of the lateral lemniscus(nLL) and nucleus mesencephalicus lateralis, pars doraslis (MLd) on both sides of the brain consistently; retrogradely labelled cells were found in contralateral OS and bilateral nucleus angularis (NA). The labelled fibers and terminals in the contralateral nLL are denser than that in ipsilateral one. The HRP labelled cells in the ipsilateral NA are more than that in the contralateral one. These results show that: (1) OS mainly receives afferents from the ipsilateral NA. This corresponds with other studies. (2) OS proJects mainly to the contralateral nLL, which hasnot been previously reported. OS also projects bilaterally to MLd. (3) OS sends descending efferents to the ipsilateral NM. This indicates thai auditory descending pathways which has been demonstrated in mammalian species may exist in birds. (4) There are commissural connections between OS on the both sides of the brain.In short, according to the evidence from the study, we presume that OS not only involves in auditory ascending projection but also may play an important role in the integration of auditory information.