Individual differences in neural regions functionally related to real and imagined stuttering

► Event-related fMRI study on stuttering in 4 individuals. ► Comparison between effects of overt stuttering and covert stuttering. ► Evidence of high intra-participant agreement for voxels activated during two different scanning occasions. ► Findings did not show strong overlap between regions activated during overt and covert stuttering. ► Results confirm findings of substantial individual differences in stutter-related neural activity. Recent brain imaging investigations of developmental stuttering show considerable disagreement regarding which regions are related to stuttering. These divergent findings have been mainly derived from group studies. To investigate functional neurophysiology with improved precision, an individual-participant approach (N=4) using event-related functional magnetic resonance imaging and test–retest reliability measures was performed while participants produced fluent and stuttered single words during two separate occasions. A parallel investigation required participants to imagine stuttering or not stuttering on single words. The overt and covert production tasks produced considerable within-subject agreement of activated voxels across occasions, but little within-subject agreement between overt and covert task activations. However, across-subject agreement for regions activated by the overt and covert tasks was minimal. These results suggest that reliable effects of stuttering are participant-specific, an implication that might correspond to individual differences in stuttering severity and functional compensation due to related structural abnormalities.