Spatiotemporal signatures of an abnormal auditory system in stuttering

Abstract

People who stutter (PWS) can reduce their stuttering rates under masking noise and altered auditory feedback; such a response can be attributed to altered auditory input, which suggests that abnormal speech processing in PWS results from abnormal processing of auditory input. However, the details of this abnormal processing of basic auditory information remain unclear. In order to characterize such abnormalities, we examined the functional and structural changes in the auditory cortices of PWS by using a 306-channel magnetoencephalography system to assess auditory sensory gating (P50m suppression) and tonotopic organization. Additionally, we employed voxel-based morphometry to compare cortical gray matter (GM) volumes on structural MR images. PWS exhibited impaired left auditory sensory gating. The tonotopic organization in the right hemisphere of PWS is expanded compared with that of the controls. Furthermore, PWS showed a significant increase in the GM volume of the right superior temporal gyrus, consistent with the right tonotopic expansion. Accordingly, we suggest that PWS have impaired left auditory sensory gating during basic auditory input processing and that some error signals in the auditory cortex could result in abnormal speech processing. Functional and structural reorganization of the right auditory cortex appears to be a compensatory mechanism for impaired left auditory cortex function in PWS.

Attention Fine-Tunes Auditory–Motor Processing of Speech Sounds

“…The spatiotemporal characteristics of the increased response are similar to the P50m (i.e., magnetic P1/P50) response, which is particularly prominent during auditory processing in infancy and suppressed during maturation (Sharma et al, 1997;Sussman et al, 2008), perhaps because of the development of connections between the auditory cortex and other cortical areas, such as the speech motor system. Sensory-gating studies demonstrate that the P50m response is increased in schizophrenics who experience auditory hallucinations (Smith et al, 2013) and in stutterers (Kikuchi et al, 2011), possibly reflecting abnormal corticocortical interactions. Thus, the increased P50m observed here might be a sign of reduced efficiency of auditory processing attributable to disrupted cortical interactions.…”

The Neurobiological Grounding of Persistent Stuttering: from Structure to Function

“…The remarkable right hemisphere over-activation in stuttering suggests an imbalanced hemispheric lateralization [28,29]. It is not yet clear whether this imbalance causes stuttering, whether it is the result of impeded left fronto-parieto-temporal signal processes, or if it reflects compensatory mechanisms [31,78,84,[88][89][90].…”

Atypical central auditory speech-sound discrimination in children who stutter as indexed by the mismatch negativity

“…recent magnetoencephalography (MEG) study, Kikuchi et al (2011) and Kikuchi, Umezaki, and Komune (2013) have offered an alternative hypothesis, linking the reduced auditory activation (suppression of P50, which is a magnetoencephalographic correlate of P1) to deficient sensory gating in the left hemisphere, accompanied by compensatory restructuring in the right hemisphere. However, most of these studies have been done with adults.…”