A Golgi study on the zona incerta of the mouse.

Abstract

The zona incerta (ZI) of the mouse was studied by the rapid Golgi method. In the ZI, small and medium-sized neurons were recognized. The former were the main constituents; their soma were fusiform or piriform in shape (15.5×22 μm) and had 4 to 8 primary dendrites. Dendrites of the small neurons in the regions near the ventral and dorsal margins of the ZI ran medially and laterally along the margins of the ZI. The mediumsized neurons were seen in the central ZI portions at the caudal levels of the ZI; they had polygonal or fusiform cell bodies (25×31 μm) which emitted 5 to 9 primary dendrites. Some dendrites of the ZI neurons extended into the ventral lateral geniculate nucleus (LGNv), the nucleus of the field of Forel (FF), the cerebral peduncle and the internal capsule. On the other hand, some dendrites of neurons in the LGNv and FF extended into the ZI. Most axons of the ZI neurons coursed dorsally, and some of them could be traced into the medial lemniscus or the dorsal thalamus. A few neurons in the regions near the ventral margin of the ZI sent axons ventrally into the cerebral peduncle. Afferent fibers to the ZI were traced from the cerebral peduncle, internal capsule, field H1, medial lemniscus and dorsal thalamus. Collaterals of fibers in the Meynert's commissure and field H2 entered the ZI. Fibers passing through the LGNv also entered the ZI. Additionally, terminal collaterals were observed to arise from fibers running mediolaterally in the ZI. Some fibers were found to send terminals commonly to the ZI, FF and LGNv by way of axon collaterals.