Inhibitory Control of Lexical Selection in Adults who Stutter

Based on previous evidence that lexical selection may operate differently in adults who stutter (AWS) versus typically-fluent adults (TFA), and that atypical attentional processing may be a contributing factor, the purpose of this study was to investigate inhibitory control of lexical selection in AWS.

12 AWS and 12 TFA completed two tasks. One was a picture naming task featuring High and Low Agreement object naming. Naming accuracy and reaction times (RT), and event-related potentials (ERPs) time-locked to picture onset, were recorded. Second was a flanker task featuring Congruent and Incongruent arrow arrays. Push-button accuracy and RTs, and ERPs time-locked to arrow array onset, were recorded.

Low Agreement pictures were named less accurately and slower than High Agreement pictures in both Groups. The magnitude of the Agreement effect on naming RTs was larger in AWS versus TFA. Delta-plot analysis revealed that the Agreement effect was positively correlated with individual differences in inhibition in TFA but not in AWS. Moreover, Low Agreement pictures elicited negative-going ERP activity relative to High Agreement pictures in both Groups. However, the scalp topography of this effect was markedly reduced in AWS versus TFA. For the Flanker task, Congruency affected push-button accuracy and RTs, and N2 amplitudes, similarly between groups.

Results point to a selective deficit in inhibitory control of lexical selection in AWS. Potential pathways between diminished inhibitory control of lexical selection, speech motor control and stuttering are discussed.