"Deep" language disorders in nonfluent progressive Aphasia: an evaluation of the "summation" account of semantic errors across language production tasks.

This study focuses on the pattern of impairments seen in a new case KT, diagnosed with nonfluent progressive aphasia (NFPA), a degenerative disorder of language production. A systematic examination of KT's performance on a wide range of language production tasks (i.e., repetition, reading, spelling, spoken and written naming) determined that both written naming and repetition were better preserved than reading, spelling-to-dictation, and spoken naming. Closer examination of error performance in both reading aloud and written production revealed evidence of "deep dyslexia" and "deep dysgraphia" that has not been documented in previous cases of NFPA, and as such the present case represents the first detailed case study of this pattern of impairment in the context of progressive aphasia. An evaluation and discussion of such deep language impairment disorders in the context of other cases of NFPA has been undertaken with reference to the summation hypothesis proposed by Hillis and Caramazza (1991, 1995). It is suggested that as a principle that holds across all language production tasks, this account can encompass patterns of deep disorders thus far reported in NFPA, although other theoretical hypotheses cannot be excluded.