| Abstract: |
Individuals with severe apraxia of speech can improve verbalization with intensive training. However, when phonemes are trained in succession, improvements often overgeneralize to inappropriate untrained contexts. We investigated whether training multiple phonemes concurrently would result in increased production of trained phonemes with less overgeneralization to untrained contexts. Our subject, HH, had severe apraxia of speech following a large left hemisphere stroke. Prior to treatment, HH produced only stereotypic /w/-initial syllables for most verbal responses. HH received intensive training incorporating motor, tactile, and auditory cueing in a hierarchy from isolated consonant to alternating consonant-vowel syllables for three phonemes, /p, t, k/. In daily probes, we tested imitation of words incorporating trained phonemes and untrained /b, d, g, f/. Treatment led to improved imitation for trained /p/ and /t/, and generalization of /p/ to /b/ and /t/ to /d/. No improvements were evident for trained /k/, or untrained /f/ and /g/. HH produced overgeneralizations of /t/ and occasionally /p/ to these phonemes. These findings suggest that overgeneralization occurred when training helped to establish a limited set of motor patterns that HH drew upon in contexts in which he lacked an adequate motor program for pronunciation of the intended phoneme. |
