SUMMARY Spoken language is a central part of our everyday lives, but the precise roles that individual cortical regions play in the production of speech are often poorly understood. To address this issue, we focally lowered the temperature of distinct cortical regions in awake neurosurgical patients, and we relate this perturbation to changes in produced speech sequences. Using this method, we confirm that speech is highly lateralized, with the vast majority of behavioral effects seen on the left hemisphere. We then use this approach to demonstrate a clear functional dissociation between nearby cortical speech sites. Focal cooling of pars triangularis/pars opercularis (Broca’s region) and the ventral portion of the precentral gyrus (speech motor cortex) resulted in the manipulation of speech timing and articulation, respectively. Our results support a class of models that have proposed distinct processing centers underlying motor sequencing and execution for speech.

Purpose Single-case experimental designs are widely used to study interventions for communication disorders. Traditionally, single-case experiments follow a response-guided approach, where design decisions during the study are based on participants' observed patterns of behavior. However, this approach has been criticized for its high rate of Type I error. In masked visual analysis (MVA), response-guided decisions are made by a researcher who is blinded to participants' identities and treatment assignments. MVA also makes it possible to conduct a hypothesis test assessing the significance of treatment effects. Method This tutorial describes the principles of MVA, including both how experiments can be set up and how results can be used for hypothesis testing. We then report a case study showing how MVA was deployed in a multiple-baseline across-subjects study investigating treatment for residual errors affecting rhotics. Strengths and weaknesses of MVA are discussed. Conclusions Given their important role in the evidence base that informs clinical decision making, it is critical for single-case experimental studies to be conducted in a way that allows researchers to draw valid inferences. As a method that can increase the rigor of single-case studies while preserving the benefits of a response-guided approach, MVA warrants expanded attention from researchers in communication disorders.

Purpose To document the efficacy of ultrasound biofeedback treatment for misarticulation of the North American English rhotic in children. Because of limited progress in the first cohort, a series of two closely related studies was conducted in place of a single study. The studies differed primarily in the nature of tongue-shape targets (e.g., retroflex, bunched) cued during treatment. Method Eight participants received 8 weeks of individual ultrasound biofeedback treatment targeting rhotics. In Study 1, all 4 participants were cued to match a bunched tongue-shape target. In Study 2, participants received individualized cues aimed at eliciting the tongue shape most facilitative of perceptually correct rhotics. Results Participants in Study 1 showed only minimal treatment effects. In Study 2, all participants demonstrated improved production of rhotics in untreated words produced without biofeedback, with large to very large effect sizes. Conclusions The results of Study 2 indicate that with proper parameters of treatment, ultrasound biofeedback can be a highly effective intervention for children with persistent rhotic errors. In addition, qualitative comparison of Studies 1 and 2 suggests that treatment for the North American English rhotic should include opportunities to explore different tongue shapes, to find the most facilitative variant for each individual speaker.

This study develops the hypothesis that the child-specific phenomenon of positional velar fronting can be modeled as the product of phonologically encoded articulatory limitations unique to immature speakers. Children have difficulty executing discrete tongue movements, preferring to move the tongue and jaw as a single unit. This predisposes the child to produce undifferentiated linguopalatal contact, neutralizing the coronal-velar contrast. Adopting a phonetically sensitive model of phonology, I propose that children's difficulty with discrete tongue movement can be encoded in a violable constraint, Move.as-Unit. The positional nature of fronting reflects the fact that discrete lingual movement is penalized more heavily in the motorically challenging context of a larger gesture. This analysis is supported with a longitudinal study of one child (3 ; 9 to 4 ; 4) whose fronting was conditioned by both segmental and prosodic factors. Adopting Move.as-Unit in a Harmonic Grammar framework makes it possible to reframe disparate-seeming conditioning factors as a unified grammatical system.

This study examined inexperienced listeners' perceptions of children's naturally produced /r/ sounds with reference to levels of accuracy determined by consensus between two expert clinicians. Participants rated /r/ sounds as fully correct, distorted or incorrect/non-rhotic. Second and third formant heights were measured to explore the relationship between acoustic cues and perceptual judgments. Inexperienced listeners' agreement was greater for correct productions than for distorted or incorrect/non-rhotic productions. In addition, inexperienced listeners' differentiation of intermediate versus fully incorrect /r/ had lower sensitivity and specificity relative to an acoustically defined threshold than experienced listeners' classification. These findings are consistent with results of previous studies highlighting the difficulty in identifying gradations of correctness in misarticulated /r/, and they suggest that this ability may be influenced by clinical experience. Additionally, all listeners were noted to be more consistent in rating vocalic /r/ than consonantal /r/. Implications for clinician training and treatment planning are discussed.