Abstract Neuronal plasticity forms the basis of our life­long ability to learn and adapt to new chal­lenges. Plasticity in adulthood, however, is of­ten limited and learning becomes increasing­ly laborious. Using a combination of behav­ioral tests and imaging of brain activity, we investigate in the visual system of mice how learning and plasticity change in the course of aging and after lesions and modify the structure and function of nerve cell networks. We hope that answering these key questions not only helps to understand the rules under­lying brain development, functioning, and learning, but will additionally open up new avenues to develop clinically relevant con­cepts to promote the regeneration and re­habilitation for diseased and injured brains. Our research has revealed clear evidence for a prominent influence of long-ranging neuro­nal interactions on cortical function and plas­ticity: they play a major role for the develop­ment of functional cortical architecture, and lesions in one cortical area affect function not only in the directly injured region but also in distant regions even on the opposite brain hemisphere.