An fMRI study of initiation and inhibition of manual and spoken responses in people who stutter

Description: Developmental stuttering is characterised by difficulties initiating speech and frequent interruptions to the flow of speech. Neuroimaging studies of speech production in people who stutter consistently reveal greater activity of the right inferior frontal cortex, an area robustly implicated in stopping manual and spoken responses. This has been linked to an “overactive response suppression mechanism” in people who stutter. Here, we used fMRI to investigate neural differences related to response initiation and inhibition in people who stutter during performance of the stop-signal task in both the manual and speech domains. We hypothesised there would be increased activity in a network centred on right inferior frontal cortex. Behaviourally, people who stutter were slower than controls to respond to ‘go’ stimuli in both domains, but the groups did not differ in their stop-signal reaction times in either domain. During the fMRI task, both groups activated the expected networks for the manual and speech tasks. Contrary to our hypothesis, we did not observe differences in task-evoked activity between people who stutter and controls during either ‘go’ or ‘stop’ trials. Using targeted, region-of-interest analyses in the inferior frontal cortex, the supplementary motor area and the putamen bilaterally, we confirmed that there were no group differences in activity. Our findings indicate a lack of support for an “overactive global inhibition mechanism” in people who stutter Behavioural data is available on OSF at https://osf.io/zjswa/