SPARING OF VERBS AND PRESERVED, BUT INEFFECTUAL READING IN A PATIENT WITH IMPAIRED WORD PRODUCTION

We report a patient who, following a left fronto-temporal lesion, show ed a complete sparing of the semantic store and a deficit of word prod uction characterized by two types of dissociations. First, oral and wr itten output was severely disrupted in naming and partially impaired i n repetition, writing to dictation and oral spelling, with the excepti on of verbs, which were normally produced in every modality and condit ion of stimulation. Second, reading was normal for all type of words a s well as non-words. This pattern of deficits suggests two functional lesions, one affecting the connections between the semantic store and the phonological lexicon and the other damaging the sublexical route t hat converts sound to sound and sound to print. It also implies that w ords are independently organized in the phonological lexicon, based on their grammatical class and have discrete connections with the semant ic store. However, CT scan evidence does not support the hypothesis th at this functional dissociation finds its anatomical correlate in the specialization of the frontal premotor cortex for verbs and the antero -medial temporal cortex for nouns. In spite of his normal reading perf ormance, both in terms of comprehension and of accuracy and speed in w ord production, the patient complained that he met with great difficul ty in reading newspapers and books, to the point that he had to renoun ce to this previously favourite activity. It was found that it took hi m time and effort to grasp the meaning of complex sentences and passag es and it was speculated that, contrary to single words and elementary sentences, comprehension of this type of material cannot be achieved by the mere access of ortographic stimuli to semantics, but requires t he retrieval of word-forms. It would appear that a patient, whose lexi cal route is blocked, can only read passages, by first converting prin t to sound via the sublexical route and then re-entering the semantic store with oral input.