Semantic capacities of the right hemisphere as seen in two cases of pure word blindness

Two patients with pure alexia were studied with tachistoscopically presented stimuli to examine factors influencing their ability to distinguish words from nonwords and to derive semantic information at exposures too brief for explicit letter identification. Both patients had profound right hemianopia and computerized tomography (CT) evidence of splenial destruction. Both patients were successful in making word/nonword decisions for high-frequency, but not low-frequency, words. They could judge semantic class membership reliably for such common categories as animals and vegetables, but not for arbitrarily selected categories, such as office-related items. Judgments about the gender of people's names and place versus person name distinctions were made with high reliability. Results are interpreted as evidence for limited word recognition and semantic-processing capacity in the right hemisphere.