Spinocerebellar tracts in the brush-tailed possum, Trichosurus vulpecula

Abstract

The direct projections of the spinal cord onto the cerebellar cortex were traced using Nauta method following the placement of cervical or thoracic spinal cord hemisections in six brush-tailed possums. Degenerating fibres reached the cerebellum via typically placed dorsal and ventral spinocerebellar tracts. Although complete differentiation of the terminations of ventral and dorsal tracts was not possible, it was found that the dorsal tract terminates mainly in the ipsilateral anterior lobe ermis and in the pyramis and paraflocculus of the ipsilateral posterior lobe. The ventral tract ends almost entirely in the anterior lobe with the majority of fibres terminating contralateral to the side of the hemisection. Within the anterior lobe, degenerating fibers were distributed fairly symmetrically about the midline in five sagittal rows. Three such rows were found in the posterior lobe. The relatively small number of rows in the anterior lobe (five) may be a characteristic feature of marsupials when compared with eutherian mammals.