Substrates of speech treatment-induced neuroplasticity in adults and children with motor speech disorders: A systematic scoping review of neuroimaging evidence

Purpose: Neuroimaging may provide clinical evidence for speech treatment-induced neuroplasticity. This review aimed to report the current scope of evidence relating to brain changes identified using neuroimaging techniques, following effective speech intervention in adults and children with motor speech disorders (MSD). Method: Studies were retrieved from five electronic databases (PubMed, CINAHL, EMBASE (Medline), SCOPUS, and Web of Science) and a general internet search. Result: Seven studies met the inclusion criteria. Using structural or functional neuroimaging techniques, five studies reported on the effects of the Lee Silverman Voice Treatment for dysarthria in adults and children, one study on the outcome of rhythmic-melodic voice training in adults with apraxia of speech, and one study on the effects of Prompts for Restructuring Oral Muscular Phonetic Targets therapy in children with idiopathic apraxia of speech. Identified brain changes included: enhanced white matter tract integrity; normalisation of baseline cortical activity; right-hemisphere shifts in re-organisation; perilesional activations; and cortical thinning. Conclusion: The current review identified preliminary evidence for treatment-dependent brain changes in adults and children with MSD. Although important to interpret within the context of Phase I research, the identification of therapeutic effects across seven heterogeneous studies suggests that treatment-induced improvements in speech performance are underpinned by demonstrable alterations in brain structure and/or function. Future research is required to better define these mechanisms of neuronal re-organisation in individuals receiving treatment for MSD, including their prognostic potential.