Stammering in adults

Research based at Oxford University

The Trust is delighted to have been funding Birtan Demirel’s PhD at St Anne’s college, Oxford since the autumn of 2021, where he is supervised by Professor Kate Watkins and Professor Charlotte Stagg. Birtan’s research includes several very valuable strands, including:

· Analysis of the incomplete cerebral dominance theory in people who stammer. Findings show no discernible differences in language lateralisation. This study will shortly be submitted to a scientific journal. Last year Birtan won an award at the 8th International Speech Motor Control Conference for this work.

· Mega-analysis of 4 studies into differences in brain activity during sentence repetition in people who stammer. Preliminary findings suggest functional differences in the brain linked to speech-motor control. This study has been approved for presentation at the 13th Oxford Dysfluency Conference.

· Evaluation of the efficacy of transcranial alternating current stimulation (tACS) combined with theta-gamma phase-amplitude coupling in enhancing sensorimotor learning during speech production. Pilot testing has commenced and in-principle acceptance has been received from the Neurobiology of Language journal.

· Investigations into the pioneering methods Birtan has developed for eliminating stammering during presentations, and which he demonstrated at the Trust Quiz Night last year. Pilot testing and data collecting began during the summer and 5 out of 7 participants have utilised the method successfully so far. Data collection will be completed by the new year. Once the study is published, Birtan aims to create an instructional video for sharing on digital media platforms so that, potentially, thousands of others can benefit from it.

· Recording of brain activity while individuals who stammer engage in tasks related to the timing of movements and articulation and investigating brain activity just before speech, to discover differences between stammered and fluent utterances. Structural MRI scans are acquired and quantitative analysis of brain tissue is conducted to investigate the concentration of iron levels in the basal ganglia – a region important for movement initiation.Once complete by the end of the year, this study will also be submitted to a scientific journal.

· Working alongside Dr Oiwi Parker Jones, using advanced machine-learning techniques to decode speech from brain activity and uncover the hidden effort and brain activity that those who stammer experience before initiating speech.

In addition to his research, Birtan continues to offer tutorials in Neurophysiology to undergraduates in Oxford. 

Birtan has been active in raising awareness and was recently interviewed about his research by BBC News and featured on BBC Six and Ten O’Clock as well as BBC UK’s social media channels. He was also able to highlight  the method
he is developing to eliminate stammering during presentations. 

Birtan has also founded the Oxford Stammering Support Group, aimed at providing support within the community.

Brain imaging research

Researcher Naheem Bashir, funded by UCL and the DBT is exploring the brain basis of stammering, and methods of reducing speech difficulty and enhancing therapy in people who stammer, using brain stimulation techniques. Over the course of his PhD, he has conducted brain stimulation studies with both fluent speakers and people who stammer and demonstrated that brain stimulation can be used to enhance speech production processes in both groups. He has also conducted brain imaging studies using Functional NearInfrared Spectroscopy (fNIRS) with people who stammer and also with fluent speakers, assessing brain activity within a face-to-face conversation style task. Having won the Rogue Resolutions Brainbox Initiative Research Challenge, Naheem was loaned fNIRS-EEG brain imaging equipment which he used to conduct new studies. In future, Naheem aims to use brain imaging to enhance understanding of the mechanisms behind stammering and find reliable targets for brain stimulation to reduce stammering. Commenting Naheem says: “Support from the DBT has been vital in allowing me to develop this research and it’s a relationship I hope will continue. I am now starting pilot work that will provide the foundation for a post doc application which will include a NIRS-EEG study and a NIRS-Virtual Reality experiment using the Brainbox equipment (pictured) with the aim of developing a closed-loop brain stimulation system.” In addition to his scientific research, Naheem raises awareness of speech impediments through UCL panel discussions, appearing in a ‘Stambassador video for Action for Stammering Children, speaking at diversity events and even educating audiences through stand-up comedy.

Stammering and attentional performance

Dr Silviya Doneva has been working with the DBT since 2015 as a research associate examining the relationship between stuttering and attentional ability. Together with Prof. Penny Cavenagh, University of Suffolk (UoS) and Dr Steve Davis, UCL, Silviya first conducted a primary research project which showed that people who stutter performed significantly worse on tasks tapping into visual selective and divided attentional resources. The results also revealed a negative association between stuttering severity and performance on two Test of Everyday Attention (TEA) subtests measuring visual selective attention. This study was published in the Journal of Clinical and Experimental Neuropsychology and presented at the 11th Oxford Dysfluency Conference.

The team, together with Sarah Costelloe had also conducted a very similar project which revealed an overall tendency for children who stutter (CWS) to score lower than children who do not stutter (CWDS) on all 13 TEA measures of the children’s version of the test (TEA-Ch). A second revision of the article has been accepted for publication by Applied Neuropsychology: Child for consideration. Building on the work to date, the trust is currently funding Silviya to conduct a meta-analytic review on adult stuttering and attentional ability. A thorough search of the literature has already been conducted amongst three of the most popular research engines: PubMed, Web of Science and Science Direct. Each of the chosen search terms: attention, vigilance, inhibitory, inhibition, interference, executive and processing, was cross-referenced with one of the following words at a time: stutter, stammer, speech disfluency and speech dysluency. A total of 22 articles met the criteria for inclusion in the review. After the meta-analysis is completed and the results are written up, the review will be submitted for publication to an academic journal.

Brain imaging research into stammering and speech mechanisms

Thanks to a very generous donation from the Mackie Foundation, the Trust is delighted to be co-financing a PhD with UCL which is investigating the Impact of Transcranial Direct Current Stimulation (tDCS) on Speech Fluency. Researcher Naheem Bashir, supervised by Professor Pete Howell, is investigating the effect of stimulating the brain with transcranial direct current stimulation (tDCS) in conjunction with the use of conventional treatment for stammering. He has so far shown that this combination does seem to work to improve speech in fluent speakers, so providing proof of the principle that tDCS can have a positive effect on speech mechanisms. There are several lines of research that Naheem is following. One study involves tDCS as an adjunct to conventional therapy. Another study currently being planned aims to assess if tDCS is more effective when delivered during or before an assessment. A further study will involve using a brain imaging system (NIRS) to look at assessing brain activity in real-time in social situations, as well as fluency enhancing situations, in people who stammer. Naheem hopes this will give an insight into the mechanisms of stuttering, as well as fluent speech production in people who stutter, and an insight into variations in speech fluency levels experienced by people who stutter in various different situations, for example high fluency when speaking alone as compared to low fluency when introducing oneself to a stranger. This could possibly provide new neural targets for treatment and have exciting implications for use in therapy.

Research on Attention and Stammering in Adults

Researcher Silviya Doneva has recently completed a year-long research project investigating the links between attention and stammering in adults, funded by the Trust and supervised by Professor Penny Cavenagh at University Campus Suffolk. This builds on earlier work undertaken at UCS, which found that children who stammer may also experience difficulties with sustaining attention. Silviya has been testing the hypothesis that stammering interferes with control of processing information and thereby affects the performance of everyday tasks. She has found a difference in attention between people who stammer and people who are fluent speakers and that people who stammer have more difficulty in sustaining attention when undertaking tasks. Although her research suggests a link between the severity of a stammer and difficulties with attention, it is not clear which is cause and which is effect. The project, which was carried out at both UCS and UCL, to ensure the population was fairly represented, was completed in May 2016 and submitted to a high-impact academic journal on fluency disorders. The findings have been presented at the 30th World Conference of the International Association of Logopedics and Phoniatrics (August 2016) and sparked local interest. The team expressed their thanks to City Lit’s Rachel Everard, BSA’s Norbert Lieckfeldt and Allan Tyrer – for raising awareness and aiding recruitment – and Professor Peter Howell for providing a testing venue in London; also to the Trust and all the participants.