Enhancing speech fluency with non-invasive brain stimulation in Developmental Stuttering

Communication is a key skill for maintaining employment, social relationships and a sense of wellbeing. Over 1 million children in the UK have a communication disorder. For many children, the communication difficulties they experience during development are successfully treated with Speech and Language Therapy. However, for some people these difficulties continue into adulthood. For adults, speech disorders carry particular negative connotations that may affect their mental wellbeing and achievement of life goals. Speech and Language Therapy can support adults with speech disorders to communicate as effectively as possible, and also provide support for living with the disorder. However, it can be difficult to change abnormal patterns of speech that have been used since childhood, and the results can sound unnatural. Advances in Speech and Language Therapy techniques to improve speech skills could positively affect all aspects of communication, and the related psychological and social factors.

This project will investigate how a new technique for electrically stimulating the brain may improve speech abilities in people with developmental stuttering (DS). We will use a method called transcranial direct current stimulation (tDCS), which involves passing an extremely weak electrical current through the scalp and the underlying part of the brain. This electrical stimulation results in a change in brain activity, and can improve the ability to perform tasks involving the stimulated brain area. tDCS has great potential as a tool for rehabilitating a range of disorders that are understood to involve abnormalities in the brain. tDCS is already being applied to acquired communication disorders. For example, it can improve language abilities in aphasia, the communication disorder experienced following a stroke. However, the potential for improving skills in developmental speech and language disorders has not yet been studied.

The project will focus on DS, a disorder that affects the fluency of speech. This can result in avoidance and anxiety around speaking, and DS has been associated with a reduced quality of life. Brain imaging studies of DS have shown subtle differences in brain regions involved in speech production. We will consider how tDCS to these brain regions can be paired with Speech and Language Therapy techniques for increasing fluency. We are interested in how tDCS may improve therapy outcomes by increasing speech skills, and by maintaining these improvements for longer. The effects of tDCS are generally measured by considering changes in behaviour. However, an important part of this project involves measuring both changes in behaviour (speech in this case), and associated changes in brain structure and function. We will use innovative combinations of tDCS with various brain imaging approaches to achieve this aim.

This research has the novel aim to develop our understanding of tDCS as a tool to improve the treatment of developmental speech disorders. Furthermore, using tDCS in combination with brain imaging techniques will enable us to measure the changes in brain activity that support speech improvements. This will advance understanding of both tDCS, and of the brain processes involved in the speech disorder studied, DS. Positive results found here may indicate a potential broader use in speech rehabilitation, for example for children with speech disorders, or adults with acquired speech impairments following stroke or brain injury.

The main aim of this project is investigate the effects of Transcranial Direct Current Stimulation (tDCS) of motor speech brain regions to improve speech Developmental Stuttering (DS).

The study objectives are to 1) Measure behavioural changes associated with single sessions of tDCS to speech motor brain regions paired with a speech task, in DS 2) Measure neurophysiological changes resulting from this intervention, in DS 3) Measure behavioural and neurophysiological effects of tDCS paired with fluency therapy over an extended period (5 consecutive days intervention).

Methodology:
tDCS: All studies will use anodal tDCS, which increases neuronal excitability, and improve task performance. The anodal electrode will be centred on electrode position FC5 in international EEG 10-20 positioning system in left hemisphere. The electrode area (5x7cm) will cover inferior frontal cortex. The reference electrode placed on the contralateral supraorbital ridge. 1 mA direct current will be applied for 20 minutes, whilst the participant completes a speech task.

Magnetic Resonance Imaging: High resolution structural and and echo planar (functional) images of the whole head will be acquired using a 3 Tesla imaging system. A sparse sampling methodology will be used to reduce motion artefacts due to participants completing speech tasks. Concurrent tDCS with fMRI will be achieved using an MR compatible DC stimulator.

Magnetoencephalography (MEG): A wholehead 306 channel magnetometer will be used to record neuromagnetic responses in motor speech regions, whilst participants complete speech tasks.

I expect my research project to impact the health and wellbeing, and ultimately the quality of life, of people with developmental speech disorders. This benefit will be realized through investigation of transcranial direct current stimulation (tDCS) as a therapeutic adjunct, as well as increasing knowledge regarding the neural basis of developmental stuttering. I also expect that clinicians (principally Speech and Language Therapists) working with people with developmental, and acquired, communication disorders to be significant beneficiaries of this research, through the same means. Long-term, the project may contribute to shaping health services for people with communication disorders.

There is potential impact for affecting evidence-based policy, for example research and clinical policy generated by the Royal College of Speech and Language Therapists. Furthermore, Speech and Language Therapy Services have seen significant funding cuts in recent years. This research work investigates tDCS, a cutting edge approach for neural modulation, and contributes to strengthening the evidence base for interventions in communication disorders. This may positively impact allocation of future funding for Speech and Language Therapy intervention.

The project has the potential for a broader impact regarding the development of tDCS in clinical intervention. As tDCS is a new approach in neuro-rehabilitation generally, the project will contribute to the evidence base for it's effectiveness and broadening the scope for application to a developmental disorder of speech.

As the project involves a new approach that may advance the treatment of developmental stuttering, the results may be used to the advantage of charities such the British Stammering Association, to generate interest in the disorder. Finally, the project will also increase public awareness of new advances in therapy for disorders of neural origin.