Extensive topographical reorganization occurs in mammalian visual areas following a retinal lesion. This reorganization is most robust following months of recovery;however, the adaptive cortical mechanisms driving this reorganization are initiated within seconds of visual deafferentation (short-term plasticity). Very little is known abut short-term plasticity in the human visual system and even less is known about the role of feedback from higher-order visual areas in these processes. The proposed project will investigate the neural mechanisms of short-term plasticity in the human visual system, focusing on the role of cortico-cortical feedback projections. A perceptually-induced retinal scotoma (artificial scotoma) will be used to safely mimic the short-term effects of a retinal lesion. Resultant changes in visual cortical response properties will be measured using a combination of event-related potentials (ERP), transcranial magnetic stimulation (TMS), and psychophysical measurements. At the conclusion of this project we will have an understanding of the spatiotemporal dynamics of feedback in short-term plasticity and the cortical origins of these feedback signals.
Following retinal damage visual brain areas reorganize and begin responding to new inputs. The functional brain mechanisms that lead to reorganization begin within seconds of damage but are poorly understood, particularly in the human brain. Understanding these mechanisms is critical for the development of visual prosthetics and the treatment of retinal degenerative diseases. This project will investigate neural mechanisms of short-term visual adaptations in the human visual system following a loss of patterned visual input from the retina.