The Effect of Non-invasive Brain Stimulation on Language Production in Post-stroke Aphasia

The Effect of Speech and Language Therapy With and Without Transcranial Direct-current Stimulation on Discourse Production in People With Post-stroke Aphasia: a Pilot Randomised Controlled Trial

Aphasia is a language impairment caused by brain injury such as stroke that affects the ability to understand and express language, read and write due to damage in the language regions of the brain. Non-invasive brain stimulation (NIBS) techniques like transcranial direct-current stimulation (tDCS) have been found to improve aphasia treatment effects in post stroke patient populations such as improved naming abilities. However, the effect of tDCS on more functional, higher level language skills such as discourse production (i.e. story telling, giving instructions) has yet to be understood.Therefore the aim of this study is to determine the potential effectiveness of tDCS as an adjunct to speech and language therapy (SLT) to improve discourse speech production in people with post-stroke aphasia. It is hypothesised that SLT combined with tDCS will result in greater improvements in discourse language production compared to SLT on its own.

Participants randomly allocated to this group using a random number generator will receive a once weekly, 6-week block of language treatment with active tDCS.

Participants randomly allocated to this group using a random number generator will receive a once weekly, 6-week block of language treatment without active tDCS (sham)

All participants will receive a 6-week block of language treatment for improving verb retrieval in discourse production by a professional speech and language therapist. The treatment goals for this block of treatment are to 1) improve verb retrieval and language quantity and complexity in discourse production 2) improve functional communication skills and; 3) improve quality of life and psychological state in people with post-stroke chronic aphasia.

Transcranial direct-current stimulation is a non-invasive brain stimulation method that can modify spontaneous cortical activity in targeted brain regions. Anodal tDCS delivered through a positively charged electrode has been found to increase cortical excitability in a targeted brain region. The use of tDCS as an adjunct to speech and language therapy has been found to improve aphasia treatment effects in post stroke patient populations.

The main verbs and their arguments will be identified in each sentence within a language sample. A PAS complexity score will be calculated using the formula: number of arguments/number of main verbs

CETI is a valid and reliable measure of change in functional communication ability in adults with aphasia. This assessment includes 16 everyday situations such as having a one to one conversation and giving yes or no answers appropriately. Participants are asked to rate their ability in each particular communication situation using a rating scale with one end labelled as 'not at all able and the other 'as able as before

AIQ is a self-report questionnaire which utilises pictures to enable people with aphasia to communicate their experiences of aphasia. There are 8 questionnaires to select from with scales that vary in relation to gender and race. Pictorial responses can be translated into numerical scores, and then documented on a summary score sheet. The questionnaire has three sections; communication, participation and well-being/emotional state. The first section looks at activities which are commonly difficult for people with aphasia such as talking and understanding. The participation section looks at how communication difficulties arising from aphasia impact the person's ability to complete tasks in everyday life such as shopping and work. The last section looks at the emotional effect of aphasia.

HADS is a 14-item scale which assesses non-somatic anxiety and depression symptoms. Scores range from 0 to 21 for each sub-scale with a score ≥8 proposed for the identification of caseness, for both depression and anxiety.

The MoCA is a brief and easy to administer cognitive assessment. Different aspects of cognition such as memory, executive function, language, visual-spatial ability and orientation are assessed. Scores range from 0-30, where the recommended cut-off score for identifying multi-domain cognitive impairment in persons with chronic stroke is 20/30.

Inclusion Criteria: aphasia caused by a single stroke at least 6 months post stroke at least 18 years old competent English speaker prior to stroke right handed prior to stroke normal aided or unaided visual acuity willing to participate and to comply with the proposed block of intervention and testing regime. Exclusion Criteria: Persons with neurological symptoms or history of a neurological event other than their stroke contraindications to tDCS including history of epilepsy or seizures and pacemakers global/severe aphasia cognitive impairment identified by a score less than 20/30 in the Montreal Cognitive Assessment left-handed dominance prior to stroke visual problems which interfere with persons' ability to access visual materials (i.e. pictures) inability to attend sessions

All information collected will be kept confidential and stored anonymously on password protected computers used only by research staff who are part of the study. Data will be stored securely in accordance with the Data Protection Act (1998) and the General Data Protection Regulations (May 2018). Stored, anonymised data may be used for future medical and health-related studies. Anonymised data will be retained for 10 years.

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