EFFECTS OF LENGTH AND LINGUISTIC COMPLEXITY ON TEMPORAL ACOUSTIC MEASURES IN APRAXIA OF SPEECH

The purpose of this study was to examine the effects of varying length and linguistic utterance types on temporal acoustic characteristics o f the imitative speech of apraxic speakers. Vowel duration and two bet ween-word segment durations were examined during the production of thr ee response types: words, word-strings, and sentences. Three length co nditions were studied in words, two length conditions for word-strings , and three length conditions for sentences, yielding eight experiment al conditions. Apraxic speakers exhibited significantly longer vowel a nd between-word segment durations than control speakers in all conditi ons, Apraxic speakers consistently produced longer vowel and between-w ord segment durations in sentence contexts than in word contexts. Furt her, intrasubject and intersubject variability for between-word segmen t durations were substantially greater for the apraxic speakers in sen tences compared to word conditions, whereas control speakers exhibited greater homogeneity in sentence production. The differences in durati on and variability in sentence production versus word or word-string p roduction imply different mechanisms for executing motor programs for varying linguistic stimuli.