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Transcranial direct current stimulation (tDCS) over the left inferior frontal gyrus (IFG) was found to improve oral and written naming in post-stroke and primary progressive aphasia (PPA), speech fluency in stuttering, a developmental speech-motor disorder, and apraxia of speech (AOS) symptoms in post-stroke aphasia. This paper addressed the question of whether tDCS over the left IFG coupled with speech therapy may improve sound duration in patients with apraxia of speech (AOS) symptoms in non-fluent PPA (nfvPPA/AOS) more than sham. Eight patients with non-fluent PPA/AOS received either active or sham tDCS, along with speech therapy for 15 sessions. Speech therapy involved repeating words of increasing syllable-length. Evaluations took place before, immediately after, and two months post-intervention. Words were segmented into vowels and consonants and the duration of each vowel and consonant was measured. Segmental duration was significantly shorter after tDCS compared to sham and tDCS gains generalized to untrained words. The effects of tDCS sustained over two months post-treatment in trained and untrained sounds. Taken together, these results demonstrate that tDCS over the left IFG may facilitate speech production by reducing segmental duration. The results provide preliminary evidence that tDCS may maximize efficacy of speech therapy in patients with nfvPPA/AOS.

This chapter contains sections titled: What is a Prosodic Impairment? Phonetic Approach Linguistic Approach Interactional Approach Psycholinguistic Approach Prosodic Impairments in Developmental Disorders Prosodic Impairments in Acquired Disorders Future Directions References

This chapter contains sections titled: Coarticulation: The Concept Measurement of Coarticulation Coarticulation in Clinical Populations: General Issues Coarticulation in Specific Clinical Populations Conclusion References

Abstract BACKGROUND AND IMPORTANCE Apraxia of speech is a disorder of articulatory coordination and planning in speech sound production. Its diagnosis is based on deficits in articulation, prosody, and fluency. It is often described concurrent with aphasia or dysarthria, while pure apraxia of speech is a rare entity. CLINICAL PRESENTATION A right-handed man underwent focal surgical resection of a recurrent grade III astrocytoma in the left hemisphere dorsal premotor cortex located in the posterior middle frontal gyrus. After the procedure, he experienced significant long-term speech production difficulties. A battery of standard and custom language and articulatory assessments were administered, revealing intact comprehension and naming abilities, and preserved strength in orofacial articulators, but considerable deficits in articulatory coordination, fluency, and prosody—consistent with diagnosis of pure apraxia of speech. Tractography and resection volumes compared with publicly available imaging data from the Human Connectome Project suggest possible overlap with area 55b, an under-recognized language area in the dorsal premotor cortex and has white matter connectivity with the superior longitudinal fasciculus. CONCLUSION The case reported here details a rare clinical entity, pure apraxia of speech resulting from resection of posterior middle frontal gyrus. While not a classical language area, emerging literature supports the role of this area in the production of fluent speech, and has implications for surgical planning and the general neurobiology of language.

Purpose: This study aimed to compare sound production errors arising due to phonological processing impairment with errors arising due to motor speech impairment. Method: Two speakers with similar clinical profiles who produced similar consonant cluster simplification errors were examined using a repetition task. We compared both overall accuracy and acoustic details of hundreds of productions with target consonant clusters to tokens with singletons. Changes in accuracy over the course of the study were also compared. Results: In target words with consonant cluster simplification, the individual whose errors reflected phonological impairment produced articulatory timing consistent with singleton onsets. These productions improved when resyllabification was possible, but error rates were not affected by exposure. In contrast, the individual with motoric-based errors produced simplifications that contained the articulatory timing associated with clusters. Accuracy was not affected by the ability to resyllabify, but it did significantly improve following repeated production. Conclusions: Our findings reveal clear differences between errors arising in phonological processing and in motor planning that reflect the underlying systems. The changes over the course of the study suggest that error types with different sources are responsive to different intervention strategies.