Stop consonant production in isolated and repeated syllables in Parkinson's disease.

To determine if Parkinson's disease (PD) patients have increasing difficulty as speech tasks become longer or more complex, the timing and accuracy of isolated syllables and repeated sequences of syllables were studied. Acoustic measures of PD patient's syllables were similarly impaired relative to normal controls for both isolated and repeated syllable sequences. Listeners' identification scores were equally high for both types of productions. Unlike previous studies of other types of movements in PD, speech accuracy and timing does not deteriorate as items become longer or more complex.