Neural substrates of linguistic prosody: evidence from syntactic disambiguation in the productions of brain-damaged patients.

The present investigation focussed on the neural substrates underlying linguistic distinctions that are signalled by prosodic cues. A production experiment was conducted to examine the ability of left- (LHD) and right- (RHD) hemisphere-damaged patients and normal controls to use temporal and fundamental frequency cues to disambiguate sentences which include one or more Intonational Phrase level prosodic boundaries. Acoustic analyses of subjects' productions of three sentence types-parentheticals, appositives, and tags-showed that LHD speakers, compared to RHD and normal controls, exhibited impairments in the control of temporal parameters signalling phrase boundaries, including inconsistent patterns of pre-boundary lengthening and longer-than-normal pause durations in non-boundary positions. Somewhat surprisingly, a perception test presented to a group of normal native listeners showed listeners experienced greatest difficulty in identifying the presence or absence of boundaries in the productions of the RHD speakers. The findings support a cue lateralization hypothesis in which prosodic domain plays an important role.