Temporal Processing in Adults Who Stutter

Abstract

Stuttering is often thought of as simply an impairment in speech production. However, some studies have indicated that people who stutter (PWS) also experience temporal processing impairments which affect perception of speech. In particular, previous behavioral and electrophysiology (EEG) studies have demonstrated time delays in processing speech stimuli in PWS. Most research to this date has only examined these timing delays at the level of the cerebral cortex, which represents the later stages of processing. Very few studies have examined delays at the level of the brainstem, and no study has looked at processing in both the cortex and the brainstem. This study recruited adults who stutter (AWS) and adults who do not stutter (AWNS) to examine how each group processes speech at both subcortical and cortical levels. Participants completed a perceptual test to determine how well they perceived speech and underwent EEG testing to measure cortical and subcortical electrical activity while listening to speech stimuli. Compared to AWNS, AWS showed poorer neural representations of the speech stimulus in the brainstem and delays at the cortical level. Perceptual testing in AWS also seemed to show a poorer perception of phoneme boundaries in words compared to AWNS. Our research suggests that temporal processing deficits are a factor in stuttering and that these deficits arise at early levels of the auditory system. These findings might call for an update of current speech therapy methods to address the timing delays that AWS experience in speech processing.