Functional link between the superior colliculus and the cerebellum in saccade studied with multiple recording and axonal reconstruction.

通过多次记录，对上丘与小脑之间的功能联系进行了解剖学和电生理学研究。在解剖分析方面取得了重大成就。已知上丘通过下橄榄核经攀升纤维系统投射到小脑。然而，攀升纤维系统的投射模式还不是很清楚。本研究将生物素标记的葡聚糖注入大鼠下橄榄核内，完全重建了34个单一的橄榄小脑轴突。已阐明，单个下橄榄神经元的轴突平均分支产生约7个攀爬纤维，并投射到小脑皮质一个纵向带状的小区域(被称为节段)，并且大多数橄榄小脑神经轴突的侧支投射到小脑核的小区域。内侧副橄榄后半部内侧区神经元将上丘投射至小脑，投射到小脑皮质第VI小叶和第VII小叶的带状小区。另一方面，邻近的第I-V小叶和第VIII小叶由内侧副橄榄尾侧半部分较外侧区的神经元支配，可能与肢体运动控制有关。我们还重建了单个苔藓纤维的完整轨迹，这是小脑皮质的另一个主要投射系统。单个苔藓纤维在小脑内广泛分支和分布，向许多纵向带状区域突起。这些结果将为了解小脑的功能提供重要信息。此外，这些结果将有助于理解小脑的功能微区化，因为它是由小脑的输入和输出纤维的连接决定的。

Functional link between the superior colliculus and the cerebellum was studied anatomically and electrophysiologically with multiple recording. Significant achievement was attained in anatomical analyzes. It has been already known that the the superior colliculus project to the cerebellum via the climbing fiber system through the inferior olive nucleus. However, projection patterns of the climbing fiber system have not been much clarified. In this study 34 single olivocerebellar axons were reconstructed completely by labeling single axons with biotinylated dextran injected into the inferior olive nucleus of rats. It was clarified that an axon of a single inferior olive neuron ramified to produce about seven climbing fibers, on average, and projects to a longitudinal band-shaped small area in the cerebellar cortex (designated as 'segment') and that most of the olivocerebellar axons had collaterals that projected to small area of the cerebellar nuclei. The neurons in the medial area in the posterior half of the medial accessory olive, which relays the superior colliculus projection to the cerebellum, were found to project to small band-shaped areas in lobule VI and VII of the cerebellar cortex. On the other hand, neighboring lobule I-V and lobule VIII were innervated by neurons in the more lateral areas of the caudal half of the medial accessory olive, presumably concerned with the control of limb movement. We also reconstructed complete trajectories of single mossy fibers, the other main projection system in the cerebellar cortex. Single mossy fibers ramified and spread broadly in the cerebellum, projecting to many longitudinal band-shaped areas. These results would give important informations in understanding function of the cerebellum. Furthermore, these results would help to understand functional micro-compartmentalization of the cerebellum, since it is determined by the connection of input and output fibers of the cerebellum.