Case Study Stress shift in aphasia: a multiple case study

Abstract

An acoustic perceptual investigation of the Rhythm Rule (RR), a phonological 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 di erent aphasic syndromes. Subjects included two left brain damaged aphasic patients one fluent, one non fluent, one right brain damaged non aphasic patient, and one non neurological control. They were instructed to read sentences containing experimental target words ("double stressed"; e.g. fourteen) and matching control words ("initial stressed"; e.g. forty" in the presence of a clause boundary or its absence. Perceptual tests indicated that rhythmic disturbances associated with the RR emerged for the non fluent aphasic only. Acoustic analysis revealed that duration of the final syllable was the principal, auditory correlate of the RR for all talkers but the non fluent aphasic. Findings are discussed in relation to issues concerning the nature and extent of disruption of the RR, phonology and phonetics of the RR, and more generally dysprosody after brain damage.