The frontal aslant tract (FAT) is a pathway that connects the inferior frontal gyrus with the supplementary motor area (SMA) and pre-SMA. The FAT was recently identified and introduced as part of a "motor stream" that plays an important role in speech production. In this study, we use diffusion imaging to examine the hypothesis that the FAT underlies speech fluency, by studying its properties in individuals with persistent developmental stuttering, a speech disorder that disrupts the production of fluent speech. We use tractography to quantify the volume and diffusion properties of the FAT in a group of adults who stutter (AWS) and fluent controls. Additionally, we use tractography to extract these measures from the corticospinal tract (CST), a well-known component of the motor system. We compute diffusion measures in multiple points along the tracts, and examine the correlation between these diffusion measures and behavioral measures of speech fluency. Our data show increased mean diffusivity in bilateral FAT of AWS compared with controls. In addition, the results show regions within the left FAT and the left CST where diffusivity values are increased in AWS compared with controls. Last, we report that in AWS, diffusivity values measured within sub-regions of the left FAT negatively correlate with speech fluency. Our findings are the first to relate the FAT with fluent speech production in stuttering, thus adding to the current knowledge of the functional role that this tract plays in speech production and to the literature of the etiology of persistent developmental stuttering.

The emergence of awareness of stuttering has been an important factor in theoretical and clinical considerations for early childhood stuttering. The present research program is aimed at studying the development of awareness of stuttering-like disfluency in normally fluent preschool and first-grade children using responses to video speech samples. A total of 79 children in five different age groups were asked to discriminate between the speech (fluent and disfluent) of two puppets, identify with the one who speaks like them, and evaluate the disfluent and fluent speech of the puppets. It was found that from age 3, children show evidence of awareness of the disfluency used in the study, but most children reached full awareness at age 5. Also, negative evaluation of disfluent speech is observed from age 4. Theoretical and clinical implications are discussed.

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The PRISE was found to be a versatile tool for implant team clinicians who are required to assess prelinguistic skills of infants. The findings suggest that early auditory skills are related to prelexical vocalization. The data also highlighted unanswered questions related to the importance of early fitting of hearing aids on vocalization before and after implantation.