CHARACTERISTICS OF SPEAKING RATE IN THE DYSARTHRIA ASSOCIATED WITH AMYOTROPHIC-LATERAL-SCLEROSIS

The ability to alter speaking rate was studied in a group of 9 subject s with amyotrophic lateral sclerosis (ALS) and 9 age- and gender-match ed, neurologically intact controls. Subjects were instructed to speak at three different rates (i.e., habitual, twice as fast as habitual, a nd one-half as fast as habitual). Speaking rate, articulation rate, an d pause duration and frequency were calculated. The proportional incre ase in speaking rate was similar between the groups; however, the dysa rthric speakers slowed rate to a smaller extent. Articulation rate and pause duration and frequency covaried with speaking rate in a similar manner for both groups. There was evidence that dysarthric speakers s howed a greater dependence on pause duration and frequency, as compare d to articulation rate, especially when increasing rate. In addition, although it was found that the slope of the function relating phrase d uration to phrase length in syllables was statistically significant fo r both normal and dysarthric speakers, the slope of the function was s ignificantly more shallow for the dysarthric speakers. Perceptual judg ments of speaking rate indicated that dysarthric speakers spoke faster for a given physical speaking mte. Finally, results suggested that th e function relating physical to perceived speaking mte grew more rapid ly for dysarthric as compared to normal speakers. Discussion focuses o n the importance of these findings to rate manipulation therapies and models of speaking rate in dysarthric speech.