The role of high-level speech planning in rehearsal: Evidence from patients with apraxia of speech

Abstract

Six patients with a disturbance of speech planning—apraxia of speech—and ten control subjects were tested on verbal memory span and other tasks that are thought to involve articulatory rehearsal. Patients' spans were significantly reduced compared to controls. As a group, they did not show the normal effects of word length or phonological similarity on span, and they had more difficulty with written rhyme than homophone judgments. This pattern is similar to that seen in normals when tested under conditions of articulatory suppression. There was a relationship between the magnitude of the phonological similarity and word length effects and articulation rate for both patients and controls. These results are in contrast to those of other studies in which patients with dysarthria, a lower-level speech output impairment, have been tested and they suggest that the speech-based process involved in planning the articulation of speech sounds, rather than in production, plays a role in rehearsal mechanisms.