White matter pathways in persistent developmental stuttering: Lessons from tractography

Identifying novel putative genes linked to stuttering in highly multiplex Indian families using exome sequencing

“…Thus most of the genes identified form extra cellular matrix molecules, involved in signaling functions indicating overall cell communication deficits. These pathways very well coincide with findings of neuroimaging (deficits in white matter tracts) 8,29 and genetic animal studies (deficits in corpus callosum) 5 which conclude cell communication deficits as the major cause for stuttering. Shugart et al, 30 implicated, interesting candidate genes (on chromosome 18) like desmoglein/desmocolin family and neuronal cadherin 2 gene that helps in cell-cell communication and cell adhesion.…”

rTMS high frequency on the left pars operculo-orbicularis combined with orthophony improves stuttering

“…The left and right IFG pars opercularis with their ipsilateral premotor and motor regions were decreased in the left hemisphere, but tended to be increased in the right hemisphere in adults who stutter compared to fluent speakers [3,10]. Thus, over-Activation right IFG is one marker of the trait of stuttering [11] and associates with underactivation of left IFG [2,12].…”

“…For stuttering patients, it is noticed neuroanatomical abnormalities in the major white matter tracts, including the left superior longitudinal fasciculus, arcuate fasciculus, corpus callosum, corticospinal, frontal aslant tracts and cortical connections with the basal-ganglia [2]. The affected tracts connect inferior frontal regions (including ventral pre-motor and motor cortex, and inferior frontal cortex and pars opercularis) with parietal (inferior parietal lobule, supramarginal and angular gyri), and temporal cortex (superior and middle temporal gyri) [2][3]. …”

White matter microstructural differences underlying beta oscillations during speech in adults who stutter

“…FA describes the asymmetry of diffusion along the orthogonal directions, therefore providing a measure of the degree of directionality, or anisotropy, of diffusion in the underlying tissue. FA values range from 0 to 1, where 0 indicates the tensor is a perfect sphere (isotropic diffusion) and 1 indicates an infinitely elongated, cigarshaped ellipsoid (anisotropic diffusion, Kronfeld-Duenias et al, 2018). TBSS registers the diffusion images non-linearly to a lab-based custom-created target image obtained from a highresolution average of 58 healthy participants aligned to standard MNI space.…”

“…In contrast, probabilistic tractography approach, is a computational process in which the diffusion data is used to reconstruct continuous 3D trajectories based on local estimates of fiber orientations. Tract reconstruction is implemented in the native space of each participant, which makes this methodology less prone to inter-subject registration errors, and it is more sensitive than voxelwise approaches like TBSS (Ben-Shachar et al, 2007;Kronfeld-Duenias et al, 2018). In addition, future studies would benefit from including auditory cortical regions such as the superior temporal gyrus within the BGTC loop in stuttering especially as it pertains to the role of auditory feedback control.…”