Impaired reading in patients with right hemianopia

A left occipital stroke may result in alexia for two reasons, which may coe xist depending on the distribution of the lesion. A lesion of the left late roventral prestriate cortex or its afferents impairs word recognition ("pur e" alexia). If the left primary visual cortex or its afferents are destroye d, resulting in a complete fight homonymous hemianopia, rightward saccades during text reading are disrupted ("hemianopic" alexia). By using functiona l imaging, we showed two separate but interdependent systems involved in re ading. The first, subserving word recognition, involved the representation of foveal vision in the left and right primary visual cortex and the ventra l prestriate cortex. The second system, responsible for the planning and ex ecution of reading saccades, consisted of the representation of right paraf oveal vision in the left visual cortex, the bilateral posterior parietal co rtex (left > right), and the frontal eye fields (right > left). Disruption of this distributed neural system was demonstrated in patients with severe right homonymous hemianopia, commensurate with their inability to perform n ormal reading eye movements. Text reading, before processes involved in com prehension, requires the integration of perceptual and motor processes. We have demonstrated these distributed neural systems in normal readers and ha ve shown how a right homonymous hemianopia disrupts the motor preparation o f reading saccades during text reading.