Enhancing speech fluency in people who stutter

Developmental stuttering (also known as stammering in the UK) affects one in twenty children and persists to adulthood in one in a hundred. People who stutter experience disruption to the normal flow of speech. They produce frequent repetitions or prolongations of sounds, syllables and words and frequent hesitations or pauses when speech can appear blocked. Children and adults who stutter can experience restrictions in their academic and career choices and some suffer from anxiety as a result of their speech difficulties. Fluency can be achieved temporarily by people who stutter by changing the way speech is produced, for example by singing, speaking with a different accent or in time with an external stimulus, such as a metronome or another speaker. Altering the auditory feedback associated with speech production can also be effective; for example, feedback that is noisy, or altered in pitch or time (delayed) can result in almost complete fluency in some people (as portrayed in the film The King's Speech). The effectiveness of altering auditory feedback in enhancing fluency suggests that stuttering may be caused by a problem in combining motor and auditory information.

In this research study, we will use speech therapy techniques that change the way speech is produced by people who stutter and improves their speech fluency. While people undergo this therapy, we will stimulate their brain with a weak electric current. This form of stimulation is painless and can improve the amount and rate at which new skills are learned. The therapy will take place over five days. Half of the people in the study will have therapy and stimulation, while the other half will have therapy and no stimulation. The participants and the researchers will not know who is having real stimulation and who is not. We will measure the effects of this therapy and stimulation by measuring rates of stuttering, speech naturalness and attitudes to stuttering before and after the five days of treatment.

We are also interested in understanding the brain abnormalities that cause stuttering. We will use MRI brain scans to measure how brain areas involved in producing speech (motor areas) and in monitoring speech (auditory areas) communicate with each other. We expect that the communication between the motor and auditory areas will improve as speech fluency improves. MRI scans give us very detailed pictures of the brain's anatomy and its function. It can also be used to see what is happening inside our mouths when we are speaking. We will develop new ways of using MRI to scan the mouth and vocal tract during fluent speech and during stuttering. This will provide us with new information about how people who stutter control their tongue and lips and other muscles involved in speech production. As speech fluency improves, we expect that we will see differences in the brain and vocal tract images, which will provide us with another way of measuring the outcome of the speech fluency and brain stimulation training.

MRI scans are very noisy and are not ideal for looking at the sensitivity of the brain areas involved in listening to speech. Also, speech is produced and understood extremely rapidly (10-12 speech sounds per second are typical in fluent speech). MRI cannot capture these rapid changes so it is necessary to use another brain imaging method called magnetoencephalography (MEG). MEG measures brain waves with very precise timing. In people who stutter, researchers have shown using MEG that speech production can alter auditory signals in the brain and that the timing of these signals is abnormal in people who stutter. We will also use MEG while people listen to and produce speech. We hope that this work will help us to understand how altering speech feedback can improve speech fluency. Such an understanding is critical for further development of effective therapies for stuttering.

Developmental stuttering is a disorder affecting the fluency of speech, characterized by repetitions or prolongations of sounds and frequent hesitations or pauses. It affects 5% of children and persists to adulthood in about 1%. Changing the motor speech pattern in adults who stutter is a particular challenge for speech and language therapy and there is a need for novel interventions, therefore. One such intervention involves the application of transcranial direct current stimulation (TDCS) alongside speech therapy. TDCS influences brain activity by modulating neuronal plasticity through the application of weak electrical currents across the brain. Pairing TDCS with speech therapy has potential for producing larger or longer lasting effects and reducing time spent in therapy.

The first aim of our study is to evaluate the potential of TDCS combined with speech fluency training to improve outcomes in people who stutter (PWS). We will use techniques that alter speech motor patterns, typically by slowing the rate of speech while maintaining naturalness. PWS will have this training while receiving anodal TDCS over the left motor cortex for 5 days (1mA for 20 mins per day) in a double-blind randomized controlled trial. Outcomes will be measured in terms of changes to stuttering rates and naturalness ratings as well as attitudes to stuttering.

The second aim of our study is to understand how changes in sensorimotor interactions relate to changes in speech fluency in PWS. We will use MRI to measure brain structure and function during speech production. We will also image the vocal tract during fluent and dysfluent speech production and during speech motor learning. Magnetoencephalography (MEG) will provide detailed information on the timing of signals and sensorimotor interactions during speech in PWS. These studies will form additional outcome measures of the speech fluency training and brain stimulation in PWS.

Who will benefit from this research? How will they benefit?
1. People who stutter
We believe that the main beneficiaries of this research will be our research participants i.e. people who stutter and their families. These are the ones who are likely to be most interested in the proposed research and its outcomes and potentially stand to benefit the most from it. In our experience, it is helpful for people who stutter to understand more about the brain abnormalities that are found in association with this disorder. We have consulted with groups previously in an informal way about using the term "abnormalities" to describe the differences we see in the brains of people who stutter compared to people who do not. We have been told that the term is not offensive to them and that they find it useful to tell other people that the reason they stutter is because they have a brain abnormality. There has been a tendency for individuals or their parents to be blamed for stuttering (due to a nervous disposition, for example). We expect that the participants in this study will be keen to disseminate the findings of our research to other interested parties who are similarly affected by developmental stuttering. In general, the study may increase public awareness of stuttering and its neural origins.

2. Speech and Language Therapy Community
The work proposed here will shed further light on the underlying brain abnormalities associated with the disorder. It may also inform our understanding of how fluency-enhancing techniques are effective in people who stutter and whether these temporary effects can be prolonged and enhanced for effective therapy. Such an understanding would be of interest to a wider group of beneficiaries, not just the individuals who stutter, but the therapists and clinical teams that work with people who stutter and others with communication difficulties. It is likely that a better understanding of stuttering and its therapy will impact the health and wellbeing, and ultimately the quality of life, of people who stutter. Long-term, the project may contribute to shaping health services for people with communication disorders. There is potential impact for this research to affect evidence-based policy, for example research and clinical policy generated by the Royal College of Speech and Language Therapists.

3. Private sector
The potential for increased understanding of the mechanisms underlying fluency enhancing techniques such as altered auditory feedback will be of interest to the commercial sector. For example, there are a number of devices and 'apps' that can deliver altered auditory feedback as a fluency aid to people who stutter.

4. British Stammering Association (charity)
As noted in the communication plan, we maintain strong links with the British Stammering Association, a charity that disseminates important information to children, parents, teachers and employers about people who stutter. This charity is therefore another likely beneficiary of this research and will aid dissemination of our work to the wider public where it may reach people who stutter who are not involved in the research. This dissemination may increase interest in the charity, which could in turn benefit from public donations.