Speech production after unilateral brain damage: Aspects of linguistic prosody

Hemispheric specialization for the production of linguistic prosody is controversial. A review of the literature in this area suggests that the right hemisphere may be involved in the production of linguistic prosody, although the findings from various studies have been contradictory (e.g., Behrens, 1988; Baum & Pell, 1997; Pell & Baum, 1997; Van Lancker & Sidtis, 1992). Also, recent findings have implicated sentence length as a factor which may determine the relative contribution of the left and right hemispheres to the production of linguistic prosody (e.g., Behrens, 1989; Gandour, Petty, & Dardarananda, 1989). The purpose of this study was to conduct a perceptual and acoustic investigation of the effect of sentence length on the production of linguistic prosody in left hemisphere-damaged nonfluent (LHD-NFL), left hemisphere-damaged fluent (LHD-FL), and right hemisphere-damaged (RHD) patients. Specifically, LHD-NFL, LHD-FL, and RHD patients were required to produce phonemic stress contrasts (e.g., HOTdog vs. hotDOG) in sentences of increasing length. Perceptual evaluation of the productions of brain-damaged patients by normal listeners revealed that all brain-damaged patients were judged to be impaired in the production of phonemic stress. Listener accuracy for the LHD-FL group decreased with increasing sentence length. Acoustic analysis of the productions revealed that all brain-damaged groups relied heavily on the use of pause duration as an intersyllabic cue to signal phonemic stress, but could not use intrasyllabic cues, i.e., vowel duration, and F$\sb{\rm o}$, consistently to signal phonemic stress across all length conditions. The findings are discussed with respect to current theories of hemispheric specialization for speech prosody