The present proposal represents an attempt to anatomically examine 1)some possible underlying mechanisms that govern the formation of certain remodeled central nervous system connections and 2) whether such connections may provide an anatomical substrate for functional recovery. Of particular relevance to this proposal is whether two normally convergent neuronal systems can still maintain a certain degree of functional convergence in response to neonatally induced cerebral cortical damage. These particular convergent systems include descending corticopontine projections from the primary somatosensory cortex. and ascending pontine afferent projections from the dorsal column nuclei (DCN). The orthograde transport of the axonal tracer WGA-HRP will be used at the light and electron microscopic level for two major purposes. First, to examine the normal developmental pattern and synaptogenesis of pontine afferents from the DCN in relation to the maturation of corticopontine projections. This should provide the necessary framework for examining some of the possible mechanisms which underly the remodeling these particular pontine afferents undergo in response to neonatal cortical lesions. Secondly, to determine whether the formation of these remodeled cortico- and DCN- pontine projections continue to form convergent connections with specific populations of pontocerebellar projection neurons (as they do in the normal, unablated animal). The maintenance of such precise anatomical connections implies that a certain degree of functional integrity is preserved through the development of these particular aberrant connections and also provides a basis for future examination of their electrophysiological influence on pontine neurons, as well as, the influence those pontine neurons have on cerebellar function.
