EEG responses to auditory cues during speech preparation predict stuttering severity and intervention outcome

Stuttering is a variable speech disorder whose brain mechanisms remain unknown. Sensorimotor brain circuits, critical in motor-speech control, including the prediction and monitoring of speech consequences, have been linked to the disorder. Despite considerable advances, it remains unclear whether auditory neural circuits relate to stuttering severity, and whether interventions to persons who stutter can induce underlying brain changes. We employed electroencephalography (EEG), in a group of persons who stutter (PWS), in combination with auditory probes to tap onto the relevance of auditory cortical regions in stuttering severity. Participants produced flexible speech (i.e., describing pictures) and non-flexible speech (i.e., reading syllables), following an auditory cue. More pronounced P200 auditory evoked potentials in response to the auditory cues were observed in participants with more severe stuttering, mainly in the picture task. Interestingly, while speech therapy intervention led to a reduction (albeit non-significant) of the P200 potential, this reduction was marginally correlated to speech fluency improvements. Moreover, EEG response patterns discriminative of cue tone frequency (400 Hz versus 800 Hz) were also predictive of stuttering severity, suggesting the involvement of fine-grained auditory cortical processing in speech preparation and stuttering. Overall, this study confirms a relationship between auditory processing of external sounds and the mechanisms of stuttering during the preparation to speak and highlights the advantage of a picture description task to investigate the relationship between auditory evoked potentials and stuttering severity under relatively ecological conditions.