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 reorganization of the visuotopic map in primary visual cortex. Associated with this change is a strengthening of an existing plexus of long-range horizontal connections by sprouting of axon collaterals and synaptogenesis. To explore the molecular substrate of this change, we studied the expression of potential 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 elevation in their receptors. We also measured elevation of transcription factors, CaMKII, MAP2 and synapsins. These experiments provide evidence for a signal transduction cascade associated with cortical reorganization.