A Role for the Frontal Aslant Tract in Speech Planning – A Neurosurgical Case Study

Frontal and temporal white matter pathways play key roles in language processing, but the specific computations supported by different tracts remain a matter of study. A role in speech planning has been proposed for a recently described pathway, the frontal aslant tract (FAT), which connects the posterior inferior frontal gyrus to the pre-SMA. Here, we use longitudinal functional and structural MRI and behavioral testing to evaluate the behavioral consequences of a lesion to the left FAT that was incurred during surgical resection of a frontal glioma in a 60-year-old woman, Patient AF. The pattern of performance in AF is compared, using the same measures, with that in a 37-year-old individual who underwent a left anterior temporal resection and hippocampectomy (Patient AG). AF and AG were both cognitively intact preoperatively but exhibited specific and doubly dissociable behavioral deficits postoperatively: AF had dysfluent speech but no word finding difficulty, whereas AG had word finding difficulty but otherwise fluent speech. Probabilistic tractography showed that the left FAT was lesioned postoperatively in AF (but not AG) whereas the inferior longitudinal fasciculus was lesioned in AG (but not AF). Those structural changes were supported by corresponding changes in functional connectivity to the posterior inferior frontal gyrus: decreased functional connectivity postoperatively between the posterior inferior frontal gyrus and pre-SMA in AF (but not AG) and decreased functional connectivity between the posterior inferior frontal gyrus and the middle temporal gyrus in AG (but not AF). We suggest from these findings that the left FAT serves as a key communicative link between sentence planning and lexical access processes. #stuttering

Chernoff, Benjamin L., Teghipco, Alex, Garcea, Frank E., and Sims, Max H. (2018). A Role for the Frontal Aslant Tract in Speech Planning: A Neurosurgical Case Study. Journal of Cognitive Neuroscience, 30, 752-769 https://doi.org/10.1162/jocn_a_01244

[stuttering, frontal white matter, temporal white matter, language processing, frontal aslant tract, speech planning]

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About rickyWburk

Ricky W. Burk, CCC-SLP, BCS-F, is a speech-language pathologist who provides in-home therapy for adolescents and adults residing in Tennessee and Mississippi who stutter. His career includes PreK, elementary, middle, and high school practice, undergraduate & graduate faculty appointments, skilled nursing, national & international consultation, private practice, and national & international speaking presentations. He holds the American Speech-Language Hearing Association Certificate of Clinical Competence, and he is a Board Certified Specialist in Fluency Disorders. He is the ASHA Continuing Education Administrator for the National Association for Speech Fluency.
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