Molecular correlates of topographic reorganization in primary visual cortex following retinal lesions

Adult visual cortex undergoes substantial functional change as a result of alterations in visual experience. Binocular retinal lesions lead to a reorg anization of the visuotopic map in primary visual cortex. Associated with t his change is a strengthening of an existing plexus of long-range horizonta l connections by sprouting of axon collaterals and synaptogenesis. To explo re the molecular substrate of this change, we studied the expression of pot ential factors involved in neural plasticity in the area of reorganization. We found elevation in a number of factors as early as 3 days following the lesion, including neurotrophins BDNF. NT3, NGF and the insulin-like growth factor IGF-1. Associated with the changes in neurotrophin levels was an el evation in their receptors. We also measured elevation of transcription fac tors, CaMKII, MAP2 and synapsins. These experiments provide evidence for a signal transduction cascade associated with cortical reorganization.