Stress shift in aphasia: a multiple case study

An acoustic-perceptual investigation of the Rhythm Rule (RR), a phonologica l phenomenon in which adjacent stresses are adjusted to avoid 'stress clash ' (e.g. thirTEEN vs THIRteen MEN), was undertaken to identify the locus of functional impairments in speech prosody in different aphasic syndromes. Su bjects included two left brain-damaged aphasic patients (one fluent, one no nfluent), one right brain-damaged non-aphasic patient, and one non-neurolog ical control. They were instructed to read sentences containing experimenta l target words ('double stressed'; e.g, fourteen) and matching control word s ('initial stressed': e.g, forty) in the presence of a clause boundary or its absence. Perceptual tests indicated that rhythmic disturbances associat ed with the RR emerged for the non-fluent aphasic only. Acoustic analysis r evealed that duration of the final syllable was the principal, auditory cor relate of the RR for all talkers but the non-fluent aphasic. Findings are d iscussed in relation to issues concerning the nature and extent of disrupti on of the RR, phonology and phonetics of the RR, and more generally dyspros ody after brain damage.