Most of us will likely agree that the brain of a person who stammers works somewhat differently to the brain of someone who is fluent. What is not so clear, is how it is different. Earlier this year Dr Soo-Eun Chang at the University of Michigan spoke to Peter Reitzes from StutterTalk about her research on the causes of stammering. We used this opportunity to discuss the neuroscience of stammering at a recent Open Space session.
Open Spaces provide a forum for people who stammer to come together and share their experiences and views on stammering. At this particular session we chose to focus the discussion on some of the scientific developments being made in the field of stammering research and what we felt this meant for us and the wider stammering community.
Dr Chang’s research has discovered that neural connectivity is a critical factor in producing fluent speech. In her work with children, she has found that those who stammer appear to have slower connections between the brains regions that control speech. Interestingly, this difference is also seen in kids who have ‘grown out’ of their stammers.
This could mean that stammering permanently changes the activity of the brain, or it could show us that children with this type of brain activity are more likely to start stammering. Dr Chang says more data is needed before we can be certain one way or the other.
What researchers do know is that timing is an essential component of speech production. When we speak, we string together a series of movements to produce the right sounds in the right order, and at the right time. In stammering, the timing of these movements appears to be impaired so that the flow of speech is disrupted.
A brain structure, called the basal ganglia, may play a starring role in all this. Buried in the centre of the brain, one of the many functions of the basal ganglia is to control movement. Scientists think that people who stammer could have too much of a chemical, called dopamine, which interferes with the ability of the basal ganglia to provide timing cues for speech. They have shown that when people who stammer take drugs to block the action of dopamine, their speech becomes more fluent.
Dr Chang explained that there is a link between rhythm – a product of timing – and stammering. A study carried out by a different research team has found that children who stammer have a weaker sense of internal rhythm compared to those who do not stammer. When these children are provided with an external rhythm – in the form of song lyrics, for example – they are able to produce speech more fluently. This suggests that independently finding and sticking to an internal rhythm is key to speaking fluently.
These insights into the ‘stammering brain’ were met with mixed feelings among the group. Some people said they felt comforted by having a physiological explanation for why they stammer, while others were uneasy with being labelled as different by science. For me, it was almost a vindication; it has given me something to fight back with against assumptions that I may be partly to blame for my stammer.
I’m aware that a focus on science – and the drugs and treatments that may ultimately arise from it – is helping to feed our medicalised approach to biological difference. It has been argued by some in the stammering community that, instead of fixing people who fall outside the norm of fluent speech, the onus should fall on society to change its expectations of what it means to speak normally.
In an ideal world there would be room for both approaches, with science providing us with knowledge and society offering us change. Indeed, despite the group’s contrasting views, what we all seemed to share was a huge appreciation for the progress being made in stammering research and the prospect of one day having answers to our many questions. My hope is that this will be paralleled by progress outside the laboratory, too.