Developmental plasticity of selected spinocerebellar axons. Studies using the North American opossum, Didelphis virginiana.

When the thoracic spinal cord of the opossum is hemisected at postnatal day 5 or 8, but not at day 12 or later ages, spinocerebellar axons which originate from spinal border cells, the sacral/coccygeal ventrolateral nucleus, and Stilling's nucleus grow through the lesion and reach the cerebellum. The critical period for such growth is comparable to that reported previously for spinocerebellar axons originating within Clarke's nucleus and for axons of the fasciculus gracilis, but shorter than that for most descending spinal axons. It appears, therefore, that differences exist in the ability of ascending and descending axons to traverse a lesion of their spinal pathway during development.