Reduced integrity in the frontal aslant tract's premotor connections is associated with dysfluency severity in stuttering
Abstract
Stuttering is a neurodevelopmental disorder marked by impaired speech production and substantial interindividual variability in symptom severity. Although neuroimaging studies have identified abnormalities in the basal ganglia-thalamocortical circuitry, the specific white matter pathways that underpin dysfluent speech production remain poorly understood. Here, we focus on the frontal aslant tract (FAT), a dorsoventral intralobar tract connecting the superior and inferior frontal cortices and proposed to support both cognitive and motor functions. Using diffusion MRI, we first compared the quantitative anisotropy of the FAT and relevant control tracts in individuals who stutter (n = 30, mean age = 35.67, SD = 13.03) and fluent speakers (n = 22, mean age = 35.64, SD = 10.87) and observed no significant group-level differences in either hemisphere. To delineate the role of FAT subbundles in speech dysfluency, we then segmented the tract at its dorsal and ventral cortical terminations and assessed their relationships with stuttering severity (Stuttering Severity Instrument-Fourth Edition). We identified left FAT subbundles connecting the posteroventral frontal structures, particularly the rostroventral precentral gyrus and, to a lesser extent, the pars opercularis to a dorsal prefrontal region whose integrity predicts stuttering severity. The left-lateralized nature of these associations suggests that stuttering results, in part, from abnormal connectivity between prefrontal systems governing volitional control and the motor circuits engaged in speech production. Together, these findings refine current neurobiological models of stuttering by implicating frontofrontal white matter pathways underlying speech dysfluency and highlight a potential anatomical target for individualized therapeutic interventions.
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BibTeX
@article{michon2026reduced,
title = {{Reduced integrity in the frontal aslant tract's premotor connections is associated with dysfluency severity in stuttering}},
author = {Maëva Michon and Fabrice Hirsch and Ivana Didirková and Davide Giampiccolo and Marie-Claude Monfrais-Pfauwadel and Anne-Laure Lemaitre and Jérémy Deverdun and Emmanuelle Lebars and Guillaume Herbet},
journal = {PNAS Nexus},
year = {2026},
month = jul,
doi = {10.1093/pnasnexus/pgag245},
url = {https://shs.hal.science/halshs-05751636v1},
note = {CC BY-NC 4.0},
}
RIS
TY - JOUR
TI - Reduced integrity in the frontal aslant tract's premotor connections is associated with dysfluency severity in stuttering
AU - Maëva Michon
AU - Fabrice Hirsch
AU - Ivana Didirková
AU - Davide Giampiccolo
AU - Marie-Claude Monfrais-Pfauwadel
AU - Anne-Laure Lemaitre
AU - Jérémy Deverdun
AU - Emmanuelle Lebars
AU - Guillaume Herbet
PY - 2026
DA - 2026/07/17
JO - PNAS Nexus
DO - 10.1093/pnasnexus/pgag245
UR - https://shs.hal.science/halshs-05751636v1
AB - Stuttering is a neurodevelopmental disorder marked by impaired speech production and substantial interindividual variability in symptom severity. Although neuroimaging studies have identified abnormalities in the basal ganglia-thalamocortical circuitry, the specific white matter pathways that underpin dysfluent speech production remain poorly understood. Here, we focus on the frontal aslant tract (FAT), a dorsoventral intralobar tract connecting the superior and inferior frontal cortices and proposed to support both cognitive and motor functions. Using diffusion MRI, we first compared the quantitative anisotropy of the FAT and relevant control tracts in individuals who stutter (n = 30, mean age = 35.67, SD = 13.03) and fluent speakers (n = 22, mean age = 35.64, SD = 10.87) and observed no significant group-level differences in either hemisphere. To delineate the role of FAT subbundles in speech dysfluency, we then segmented the tract at its dorsal and ventral cortical terminations and assessed their relationships with stuttering severity (Stuttering Severity Instrument-Fourth Edition). We identified left FAT subbundles connecting the posteroventral frontal structures, particularly the rostroventral precentral gyrus and, to a lesser extent, the pars opercularis to a dorsal prefrontal region whose integrity predicts stuttering severity. The left-lateralized nature of these associations suggests that stuttering results, in part, from abnormal connectivity between prefrontal systems governing volitional control and the motor circuits engaged in speech production. Together, these findings refine current neurobiological models of stuttering by implicating frontofrontal white matter pathways underlying speech dysfluency and highlight a potential anatomical target for individualized therapeutic interventions.
SN - 2752-6542
ER -