Speech motor stability in IPD: Effects of rate and loudness manipulations

Increasing phonatory effort, an integral component of the Lee Silverman Voi ce Treatment, LSVT. has been identified as an effective management strategy for adults with hypokinetic dysarthria associated with Parkinsonism. The p resent study compares the effects of increased loudness on lower lip moveme nts to those of changes in speaking rate, another approach to the treatment of hypokinetic dysarthria. Movements of the lower lip/jaw during speech we re recorded from 8 adults with IPD, 8 healthy aged adults, and 8 young adul ts. The spatiotemporal index (STI), a measure of spatial and temporal varia bility revealed that for all speaker groups slow rate was associated with t he most variability. Compared to the other conditions, STI values from the loud condition were closest to those from habitual speech. Also, the normal ized movement pattern for the loud condition resembled that of habitual spe ech. It is hypothesized that speaking loudly is associated with a spatial a nd temporal organization that closely resembles that used in habitual speec h, which may contribute to the success of the LSVT.