Stammering is a common condition in children that may last into adulthood and can affect people's self-esteem, education and employment prospects.
22 October is International Stammering Awareness Day and sees the launch of a new Oxford University trial investigating whether a form of non-invasive brain stimulation could help people who stammer achieve fluent speech more easily and make this fluency last longer.
I asked Kate Watkins and Jen Chesters of Oxford University's Department of Experimental Psychology, who are leading the new trial, about the science of stammering, what the trial will involve, and how brain stimulation could improve current therapies…
OxSciBlog: What is stuttering/stammering? How many people have a stammer?
Kate Watkins: Stammering (also known as stuttering) affects one in twenty children and one in a hundred adults. About four or five times more men than women are affected.
The normal flow of speech is disrupted when people stammer. The speaker knows what he or she wants to say but has problems saying it. The characteristics of stammering include production of frequent repetitions of speech sounds, and frequent hesitations when speech appears blocked. Children and adults who stammer can sometimes experience restrictions in their academic and career choices. Some people some suffer anxiety as a result of their speech difficulties.
OSB: What do we think causes people to stammer?
KW: The cause of stammering is unknown. Using MRI scans we have noticed small differences in the brains of people who stammer when compared with those of people who speak fluently. For example, we found differences in the amount of brain activity that occurs during speech production in people who stammer even when they are speaking fluently.
These brain imaging studies indicate abnormal function of brain areas involved in planning and producing speech, and in monitoring speech production. We have also used MRI scans to look at how these brain areas are connected and found that the white matter connections between these regions are disrupted in people who stammer.
A striking feature of stammering is that complete fluency can be achieved by changing the way a person perceives his or her own speech (so by altering the way the speaker hears his or her own voice). For example, masking speech production with noise (or loud music as demonstrated in the film The King's Speech or by Musharraf on Educating Yorkshire) can temporarily eliminate stuttering. Delaying auditory feedback of speech, altering its pitch, singing, speaking in unison with another speaker, or speaking in time with a metronome are all ways of temporarily enhancing fluency in people who stammer. These observations tell us that the cause of stammering may be due to a problem in combining motor and auditory information.
OSB: What treatments/therapies can people currently get for stammering?
Jen Chesters: Speech and Language Therapy for people who stammer may involve learning to reduce moments of stammering, or decrease the amount of tension when stammering. Techniques such as speaking in time with a metronome beat, or lengthening each speech sound can immediately increase fluency.
However, these approaches make speech sound unnatural, so moving towards fluent yet natural-sounding speech is the main challenge during therapy. Even when these methods are mastered within the speech therapy clinic, continual ongoing practice is needed for fluency to be maintained in everyday life. The fluency-enhancing effects can also just 'wear off' over time, even when these techniques are practised regularly. For all these reasons, therapy for adults who stammer often focuses instead on learning to live with the disorder.
OSB: How might brain stimulation improve on these?
JC: Non-invasive brain stimulation is a promising new method for treating disorders that affect the brain's function. The method we use is called transcranial direct current stimulation (or TDCS for short). TDCS involves passing a very weak electrical current across surface electrodes placed on the scalp, and through the underlying brain tissue (it doesn't hurt!). This stimulation changes the excitability of the targeted brain area. TDCS applied during a task that engages the stimulated brain region, can increase and prolong task performance or learning.
TDCS has been used in rehabilitation studies, for example it has been applied to brain regions involved in speech and language to increase these functions in patients who have problems with speech (aphasia) following a stroke. We are interested in how TDCS could help people who stammer to achieve fluent speech more easily, and maintain their fluency for longer. TDCS may have the potential to increase speech therapy outcomes, or to reduce the high levels of effort and practice that are needed in traditional speech therapy for stammering. Our research aims to explore this potential.
OSB: What is the aim of your new trial?
JC: In this study, we want to see how the effects of a brief course of fluency therapy might be increased or prolonged by using TDCS. We will use some techniques that we know will immediately increase fluency in most people who stammer, such as speaking in unison with another person or in time with a metronome. However, these techniques would normally need to be combined with other methods to help transfer this fluency into everyday speech. We will investigate how TDCS might help maintain the fluent speech that is produced using these methods.
OSB: What will volunteers be asked to do?
JC: Volunteers will be invited to have fluency therapy over five consecutive days, whilst receiving TDCS. In order to measure the effects of this intervention, they will also be asked to do some speech tasks before the fluency therapy, one week after the fluency therapy, and again six weeks later. We are also interested in how this combination of therapy and TDCS may change brain function and structure. So, volunteers will also be invited for MRI scans before and after the therapy.
OSB: How do you hope the trial results will benefit patients/your research?
JC: The results of the trial will give us a first indication about whether TDCS might be a useful method to develop for stammering therapy. The research is in its early stages, so the results of this study will not cross over into the speech therapy clinic just yet. However, we are hoping to see whether TDCS shows promise for improving speech therapy outcomes. If it does, further research would be needed to explore how TDCS can be combined with speech therapy to achieve the greatest improvements for people who stammer.
The researchers are looking for 30 male volunteers, aged 18-50, who have a moderate to severe stammer. The trial will take place at Oxford University's Department of Experimental Psychology.
Anyone interested in taking part should contact Jen Chesters by email firstname.lastname@example.org or call 01865 271363