Reading: selective sparing of closed-class words in Wernicke's aphasia

One aspect of Broca's aphasia, induced by anterior perisylvian lesions, is an inability to read closed-class words (eg, articles, prepositions) with a preserved ability to read open-class words (eg, nouns, verbs). We examined a man with profound Wernicke's aphasia induced by an infarct of the posterior portion of the superior temporal gyrus (Wernicke's area). He could not read substantive words or pronounceable nonwords but could read closed-class words. These observations suggest that the reading of closed- and open-class words is mediated by separable systems. Whereas the anterior perisylvian region appears to be important in reading functional words, the posterior perisylvian region is important in reading substantive words.