The influence of cerebellar transcranial direct current stimulation (tDCS) on motor skill learning in swallowing.

The cerebellum is highly involved in motor skill learning and has a primary role in the coordination of movements and error correction. Transcranial direct current stimulation (tDCS) applied over the cerebellum increases cerebellar excitability and enhances motor skill learning of healthy individuals in the corticospinal system. Whether these effects also occur for corticobulbar-related motor functions like swallowing is unknown. Cerebellar tDCS, as an adjuvant technique to motor skill training in swallowing, may offer new directions for enhancing functional and physiological outcomes for neurological swallowing rehabilitation. Based on outcomes of cerebellar tDCS combined with skill training in limb function, it was hypothesised that anodal tDCS would enhance, and cathodal tDCS would inhibit motor performance and motor skill learning in this study of swallowing. In Behavioural study I, a double-blind randomised controlled trial (RCT) was performed to evaluate the effects of cerebellar tDCS on motor performance and learning in swallowing. Thirty-nine healthy adults were assigned to one of three conditions (anodal tDCS, cathodal tDCS, and sham). Two swallowing skill training sessions, with preceding cerebellar tDCS, were completed on consecutive days. The sessions consisted of a 2 mA current applied over midline cerebellum for 20 min, followed by skill training using sEMG biofeedback to target volitional control of timing and magnitude of submental muscle activation during swallowing. Similar to the corticospinal literature, cathodal tDCS inhibited motor skill learning of temporal accuracy gains compared to the sham condition (p < .05). However, anodal tDCS also inhibited the temporal aspects of motor skill learning in swallowing compared to sham (p < .05), which is in contrast to the hypotheses and the corticospinal literature. This suggests differences in the effects of cerebellar tDCS on corticobulbar and corticospinal motor functions. Furthermore, polarity dependent mechanisms of cerebellar tDCS need to be addressed in future research, since cathodal tDCS was not the behavioural inverse of anodal tDCS, as is seen in limb literature. Behavioural study II represented a preliminary exploration of cerebellar tDCS on motor performance and learning in patients with neurological impairment. In this proof-of-concept study, six patients with oropharyngeal dysphagia following stroke were randomly assigned to one of the three conditions (anodal tDCS, cathodal tDCS or sham). The same experimental procedure as in Behavioural study I was performed, however, a behavioural swallowing exam prior to commencement of the study and in the follow-up assessments was added. The assessment of swallowing skill learning, without visual feedback, was too challenging to complete in four out of the six patients. Only the patients in the cathodal group were able to complete the assessment, which hinders comparisons of learning between the three conditions in this study. Future studies will require development of an alternate measure of swallowing skill learning. All patients were able to complete the skill training protocol and the assessment of motor performance (with visual feedback). The outcomes in the assessment of performance did not change considerably from baseline in any patient over time regardless of stimulation condition. This is in contrast to the results of healthy participants in Behavioural study I where only one session of swallowing skill training was sufficient to significantly improve swallowing performance that remained over time. This indicates that two days of treatment may not be sufficient to increase swallowing performance in neurologically impaired patients. These patients may need multiple skill training sessions to increase volitional control over swallowing behaviours. The majority of studies looking at the effects of cerebellar tDCS have been performed in the corticospinal motor system and have utilised a mono-hemispheric electrode placement. This placement has been validated by showing significant changes in cerebellar excitability, i.e. a significant increase in cerebellar-brain inhibition (CBI), immediately following cerebellar tDCS. However, unlike limb motor control, swallowing involves midline structures that are bilaterally innervated by the corticobulbar motor system. Therefore, this proof-of-concept study aimed to assess, if midline placement of the tDCS electrode over the cerebellum could achieve the same for a bilaterally innervated midline function. Changes in cerebellar excitability were assessed in fifteen healthy individuals using paired-pulse TMS over the cerebellum and motor cortex by measuring MEPs from the submental muscle group and the first dorsal interosseus muscle (FDI) of the dominant hand. Although MEPs from the submental muscles at rest were reported in previous research, no reliable MEP responses from this muscle group could be collected at a reasonable stimulator output (below 80% maximal stimulator output) in the current study. There were no statistically significant differences between the active tDCS and sham group when evaluating tDCS effects of the cerebellum on the FDI motor circuits over time. This may suggest that a midline electrode placement for cerebellar tDCS of 2 mA applied over 20 minutes is not sufficient to induce neurophysiological changes within the corticospinal system. However, the lack of difference may likely be due to the large inter-individual response variability. This hypothesis is supported by findings in Behavioural study I, where behavioural inhibition was demonstrated using the same electrode placement. The results of this study provide guidance for adapted or newly developed assessment protocols that evaluate the effects of cerebellar tDCS at midline for swallowing, e.g. using pharyngeal MEP measures. This research programme was the first to investigate the use of cerebellar tDCS for motor skill learning in swallowing in healthy individuals and patients with dysphagia following stroke. Cerebellar tDCS in combination with motor skill training, using the protocol as proposed in this research programme, inhibited motor skill learning in healthy individuals and may well be contraindicated for patients in swallowing rehabilitation using skill training. Further research is required to confirm this. However, swallowing skill training without tDCS was demonstrated to improve motor performance and motor skill learning in swallowing. This provides a strong indication for future research into the potential implementation of skill training in swallowing rehabilitation

Scoping Review Protocol: Characteristics of dysphagia in people with Parkinson's Disease

PROTOCOL: Scoping Review to systematically synthesise and analyse the characteristics of oropharyngeal and oesophageal dysphagia in people with PD including the diagnostic assessment tools that have been reported

Therapeutic relationships in speech-language pathology : a scoping review protocol

Objective: The purpose of this scoping review is to provide an overview of empirical research regarding the therapeutic relationship between speech-language pathologists and their clients of all ages and clinical areas. Introduction: The influence of a positive relationship between professionals and clients on the process and outcome of interventions is well documented for many health professions. However, research in speech-language pathology predominantly focuses on the outcome of specific treatment methods and techniques. The number of empirical research studies on the therapeutic relationship within this research area is increasing. At present, existing research has not been summarized and compared. Inclusion criteria: The review will include all empirical research that addresses the therapeutic relationship between speech-language pathologists and their clients of all ages and clinical areas. Since speech-language pathologists often collaborate intensively with caregivers of their clients, such as parents or partners, these groups will also be included. Methods: Systematic searches will be conducted across seven research databases (ASHAWire, CINAHL, ERIC, Fachportal Pädagogik, LIVIVO, MEDLINE [PubMed], and PsycINFO) and four unpublished/gray literature databases (evidenssst, ndldt, OpenGrey, and SSOAR). Data will be extracted by two independent reviewers for author(s), year of publication, country of origin, research questions, participants, terminology and theoretical foundations, research design, and focus. Central findings concerning the therapeutic relationship on the input-, process-, outcome, and output-level of speech-language interventions will be analyzed. Results will be presented as a narrative summary

Scoping Review Protocol: Characteristics of dysphagia in people with Parkinson's Disease

PROTOCOL: Scoping Review to systematically synthesise and analyse the characteristics of oropharyngeal and oesophageal dysphagia in people with PD including the diagnostic assessment tools that have been reported

Therapeutic relationships in speech-language pathology: A scoping review of empirical studies

Purpose: This scoping review provides an overview of empirical studies investigating therapeutic relationships between speech-language pathologists (SLPs), clients, and caregivers across all ages and clinical areas, and identifies areas of future research. Method: The Joanna Briggs Institute’s (JBI) scoping review method was employed. Systematic searches were conducted across seven databases and four grey literature databases. Research published in English and German until 3 August 2020 was included. Data were extracted for the primary aim, terminology and theoretical foundations, research design, and focus. Central findings concerning the input-, process-, outcome-, and output-level of speech-language pathology were categorised. Result: Of 5479 articles, 44 articles were included in the analysis. Psychotherapy was the leading discipline for the theoretical foundation and measurement of relationship quality. Most findings focused on therapeutic attitudes, qualities, and relational actions to build the basis of a positive therapeutic relationship. A small number of studies indicated connections between clinical outcomes and the quality of the relationships. Conclusion: Future research needs to address precision of terminology, expansion of qualitative and quantitative research methods, development and psychometric examination of measuring instruments specific to SLPs and the development and evaluation of concepts to support professional relationship building in speech-language pathology training and everyday work.</p