Purpose This study was designed to test two hypotheses about apraxia of speech (AOS) derived from the DIVA model (Guenther et al., 2006): (1) the Feedforward System Deficit Hypothesis and (2) the Feedback System Deficit Hypothesis. Method We used noise masking to minimize auditory feedback during speech. Six speakers with AOS and aphasia, four with aphasia without AOS, and two unimpaired speaker groups (younger and older adults) participated. Acoustic measures of vowel contrast, variability, and duration were analyzed. Results Younger, but not older unimpaired speakers showed significantly reduced vowel contrast with noise masking. Relative to older controls, the AOS group showed longer vowel durations, and a greater reduction in vowel contrast under masking conditions. There were no significant differences in variability. Three of the six speakers with AOS demonstrated the group pattern. Speakers with aphasia without AOS did not differ from controls in contrast, duration, or variability. Conclusion The greater reduction in vowel contrast with masking noise for the AOS group is consistent with the Feedforward System Deficit Hypothesis but not with the Feedback System Deficit Hypothesis; however, effects were small and not present in all individual speakers with AOS. Theoretical implications and alternative interpretations of these findings are discussed.

S1: https://doi.org/10.23641/asha.5103070. S2 and S3: https://doi.org/10.23641/asha.5106508.

Results provide preliminary support for the retrieval hypothesis, suggesting that access to motor programs may be impaired in speakers with AOS. However, the possibility that the motor programs may also be damaged cannot be ruled out.

Only a handful of published studies on apraxia of speech have used reaction time methods. However, these studies have provided deeper insight into speech planning impairments in AOS based on a variety of experimental paradigms.

Purpose This study examines the effects of enhanced conversational recast for treating morphological errors in preschoolers with developmental language disorder. The study assesses the effectiveness of this treatment in an individual or group ( n = 2) setting and the possible benefits of exposing a child to his or her partner's treatment target in addition to his or her own. Method Twenty children were assigned to either an individual ( n = 10) or group ( n = 10, 2 per group) condition. Each child received treatment for 1 morpheme (the target morpheme) for approximately 5 weeks. Children in the group condition had a different target from their treatment partner. Pretreatment and end treatment probes were used to compare correct usage of the target morpheme and a control morpheme. For children in the group condition, the correct usage of their treatment partner's target morpheme was also examined. Results Significant treatment effects occurred for both treatment conditions only for morphemes treated directly (target morpheme). There was no statistically significant difference between the treatment conditions at the end of treatment or at follow-up. Children receiving group treatment did not demonstrate significant gains in producing their partner's target despite hearing the target modeled during treatment. Conclusions This study provides the evidence base for enhanced conversational recast treatment in a small group setting, a treatment used frequently in school settings. Results indicate the importance of either attention to the recast or expressive practice (or both) to produce gains with this treatment. Supplemental Material https://doi.org/10.23641/asha.7859975