What V1 Damage Can Teach Us About Visual Perception and Learning

In humans, occipital strokes invariably damage the primary visual cortex (V1), causing a loss of conscious vision over large portions of the visual field. This unfortunate experiment of nature affects a significant proportion of all stroke victims, but there is a lack of accepted vision restoration therapies clinically, despite a rich history of studies into the resulting visual deficit and the perceptual abilities that paradoxically survive in affected portions of the visual field. Over the last two decades, the clinical dogma that V1-damaged adult visual systems cannot recover has been challenged by accumulating evidence that visual retraining to detect or discriminate stimuli in the blind field can restore perceptual abilities. This review summarizes key developments in training approaches, some of the mechanistic insights they have revealed, and limitations and opportunities that have emerged.