Limits...
Combined DTI Tractography and Functional MRI Study of the Language Connectome in Healthy Volunteers: Extensive Mapping of White Matter Fascicles and Cortical Activations.

Vassal F, Schneider F, Boutet C, Jean B, Sontheimer A, Lemaire JJ - PLoS ONE (2016)

Bottom Line: Eight putative WM fascicles for language were probed using a deterministic DTI-FT technique: the arcuate fascicle (AF), superior longitudinal fascicle (SLF), uncinate fascicle (UF), temporo-occipital fascicle, inferior fronto-occipital fascicle (IFOF), middle longitudinal fascicle (MdLF), frontal aslant fascicle and operculopremotor fascicle.WM fascicle terminations were also observed beyond fMRI-confirmed language areas and reached numerous cortical areas involved in different functional brain networks.These findings suggest that the reported WM fascicles are not exclusively involved in language and might be related to other cognitive functions such as visual recognition, spatial attention, executive functions, memory, and processing of emotional and behavioral aspects.

View Article: PubMed Central - PubMed

Affiliation: IGCNC (Image-Guided Clinical Neuroscience and Connectomics), EA 7282, Unité de Formation et de Recherche Médecine, Université d'Auvergne, Clermont-Ferrand, France.

ABSTRACT
Despite a better understanding of brain language organization into large-scale cortical networks, the underlying white matter (WM) connectivity is still not mastered. Here we combined diffusion tensor imaging (DTI) fiber tracking (FT) and language functional magnetic resonance imaging (fMRI) in twenty healthy subjects to gain new insights into the macroscopic structural connectivity of language. Eight putative WM fascicles for language were probed using a deterministic DTI-FT technique: the arcuate fascicle (AF), superior longitudinal fascicle (SLF), uncinate fascicle (UF), temporo-occipital fascicle, inferior fronto-occipital fascicle (IFOF), middle longitudinal fascicle (MdLF), frontal aslant fascicle and operculopremotor fascicle. Specific measurements (i.e. volume, length, fractional anisotropy) and precise cortical terminations were derived for each WM fascicle within both hemispheres. Connections between these WM fascicles and fMRI activations were studied to determine which WM fascicles are related to language. WM fascicle volumes showed asymmetries: leftward for the AF, temporoparietal segment of SLF and UF, and rightward for the frontoparietal segment of the SLF. The lateralization of the AF, IFOF and MdLF extended to differences in patterns of anatomical connections, which may relate to specific hemispheric abilities. The leftward asymmetry of the AF was correlated to the leftward asymmetry of fMRI activations, suggesting that the lateralization of the AF is a structural substrate of hemispheric language dominance. We found consistent connections between fMRI activations and terminations of the eight WM fascicles, providing a detailed description of the language connectome. WM fascicle terminations were also observed beyond fMRI-confirmed language areas and reached numerous cortical areas involved in different functional brain networks. These findings suggest that the reported WM fascicles are not exclusively involved in language and might be related to other cognitive functions such as visual recognition, spatial attention, executive functions, memory, and processing of emotional and behavioral aspects.

Show MeSH
Schematic illustration of the language connectome.Occurrence (expressed in percentage; n = 20 healthy subjects) of connections between white matter fascicles and BOLD clusters within known essential language areas of the left (top) and right (bottom) hemispheres (3D renderings of fMRI group analysis; activations observed at individual level within the temporal pole, inferior parietal lobule and ventral premotor cortex of the right hemisphere are not shown; see text for details). AF = arcuate fascicle; AG = angular gyrus; FAF = frontal aslant fascicle; IFOF = inferior fronto-occipital fascicle; MdLF = middle longitudinal fascicle; MFG = middle frontal gyrus; MTG = middle temporal gyrus; Op = pars opercularis; OpPMF = operculopremotor fascicle; Orb = pars orbitalis; SLF-fp = frontoparietal segment of the superior longitudinal fascicle; SLF-tp = temporoparietal segment of the superior longitudinal fascicle; SMA = supplementary motor area; SMG = supramarginal gyrus; STG = superior temporal gyrus; TOF = temporo-occipital fascicle; TP = temporal pole; Tr = pars triangularis; UF = uncinate fascicle; vPMC = ventral premotor cortex.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4814138&req=5

pone.0152614.g005: Schematic illustration of the language connectome.Occurrence (expressed in percentage; n = 20 healthy subjects) of connections between white matter fascicles and BOLD clusters within known essential language areas of the left (top) and right (bottom) hemispheres (3D renderings of fMRI group analysis; activations observed at individual level within the temporal pole, inferior parietal lobule and ventral premotor cortex of the right hemisphere are not shown; see text for details). AF = arcuate fascicle; AG = angular gyrus; FAF = frontal aslant fascicle; IFOF = inferior fronto-occipital fascicle; MdLF = middle longitudinal fascicle; MFG = middle frontal gyrus; MTG = middle temporal gyrus; Op = pars opercularis; OpPMF = operculopremotor fascicle; Orb = pars orbitalis; SLF-fp = frontoparietal segment of the superior longitudinal fascicle; SLF-tp = temporoparietal segment of the superior longitudinal fascicle; SMA = supplementary motor area; SMG = supramarginal gyrus; STG = superior temporal gyrus; TOF = temporo-occipital fascicle; TP = temporal pole; Tr = pars triangularis; UF = uncinate fascicle; vPMC = ventral premotor cortex.

Mentions: The overall occurrences of WM fascicle–BOLD cluster connections within cortical territories known as essential language areas are reported in Fig 5 and S3 Table. As the analysis was performed at individual level, a number of WM fascicle–BOLD cluster connections were found within cortical territories of the right hemisphere where fMRI group analysis did not reveal areas of activations.


Combined DTI Tractography and Functional MRI Study of the Language Connectome in Healthy Volunteers: Extensive Mapping of White Matter Fascicles and Cortical Activations.

Vassal F, Schneider F, Boutet C, Jean B, Sontheimer A, Lemaire JJ - PLoS ONE (2016)

Schematic illustration of the language connectome.Occurrence (expressed in percentage; n = 20 healthy subjects) of connections between white matter fascicles and BOLD clusters within known essential language areas of the left (top) and right (bottom) hemispheres (3D renderings of fMRI group analysis; activations observed at individual level within the temporal pole, inferior parietal lobule and ventral premotor cortex of the right hemisphere are not shown; see text for details). AF = arcuate fascicle; AG = angular gyrus; FAF = frontal aslant fascicle; IFOF = inferior fronto-occipital fascicle; MdLF = middle longitudinal fascicle; MFG = middle frontal gyrus; MTG = middle temporal gyrus; Op = pars opercularis; OpPMF = operculopremotor fascicle; Orb = pars orbitalis; SLF-fp = frontoparietal segment of the superior longitudinal fascicle; SLF-tp = temporoparietal segment of the superior longitudinal fascicle; SMA = supplementary motor area; SMG = supramarginal gyrus; STG = superior temporal gyrus; TOF = temporo-occipital fascicle; TP = temporal pole; Tr = pars triangularis; UF = uncinate fascicle; vPMC = ventral premotor cortex.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814138&req=5

pone.0152614.g005: Schematic illustration of the language connectome.Occurrence (expressed in percentage; n = 20 healthy subjects) of connections between white matter fascicles and BOLD clusters within known essential language areas of the left (top) and right (bottom) hemispheres (3D renderings of fMRI group analysis; activations observed at individual level within the temporal pole, inferior parietal lobule and ventral premotor cortex of the right hemisphere are not shown; see text for details). AF = arcuate fascicle; AG = angular gyrus; FAF = frontal aslant fascicle; IFOF = inferior fronto-occipital fascicle; MdLF = middle longitudinal fascicle; MFG = middle frontal gyrus; MTG = middle temporal gyrus; Op = pars opercularis; OpPMF = operculopremotor fascicle; Orb = pars orbitalis; SLF-fp = frontoparietal segment of the superior longitudinal fascicle; SLF-tp = temporoparietal segment of the superior longitudinal fascicle; SMA = supplementary motor area; SMG = supramarginal gyrus; STG = superior temporal gyrus; TOF = temporo-occipital fascicle; TP = temporal pole; Tr = pars triangularis; UF = uncinate fascicle; vPMC = ventral premotor cortex.
Mentions: The overall occurrences of WM fascicle–BOLD cluster connections within cortical territories known as essential language areas are reported in Fig 5 and S3 Table. As the analysis was performed at individual level, a number of WM fascicle–BOLD cluster connections were found within cortical territories of the right hemisphere where fMRI group analysis did not reveal areas of activations.

Bottom Line: Eight putative WM fascicles for language were probed using a deterministic DTI-FT technique: the arcuate fascicle (AF), superior longitudinal fascicle (SLF), uncinate fascicle (UF), temporo-occipital fascicle, inferior fronto-occipital fascicle (IFOF), middle longitudinal fascicle (MdLF), frontal aslant fascicle and operculopremotor fascicle.WM fascicle terminations were also observed beyond fMRI-confirmed language areas and reached numerous cortical areas involved in different functional brain networks.These findings suggest that the reported WM fascicles are not exclusively involved in language and might be related to other cognitive functions such as visual recognition, spatial attention, executive functions, memory, and processing of emotional and behavioral aspects.

View Article: PubMed Central - PubMed

Affiliation: IGCNC (Image-Guided Clinical Neuroscience and Connectomics), EA 7282, Unité de Formation et de Recherche Médecine, Université d'Auvergne, Clermont-Ferrand, France.

ABSTRACT
Despite a better understanding of brain language organization into large-scale cortical networks, the underlying white matter (WM) connectivity is still not mastered. Here we combined diffusion tensor imaging (DTI) fiber tracking (FT) and language functional magnetic resonance imaging (fMRI) in twenty healthy subjects to gain new insights into the macroscopic structural connectivity of language. Eight putative WM fascicles for language were probed using a deterministic DTI-FT technique: the arcuate fascicle (AF), superior longitudinal fascicle (SLF), uncinate fascicle (UF), temporo-occipital fascicle, inferior fronto-occipital fascicle (IFOF), middle longitudinal fascicle (MdLF), frontal aslant fascicle and operculopremotor fascicle. Specific measurements (i.e. volume, length, fractional anisotropy) and precise cortical terminations were derived for each WM fascicle within both hemispheres. Connections between these WM fascicles and fMRI activations were studied to determine which WM fascicles are related to language. WM fascicle volumes showed asymmetries: leftward for the AF, temporoparietal segment of SLF and UF, and rightward for the frontoparietal segment of the SLF. The lateralization of the AF, IFOF and MdLF extended to differences in patterns of anatomical connections, which may relate to specific hemispheric abilities. The leftward asymmetry of the AF was correlated to the leftward asymmetry of fMRI activations, suggesting that the lateralization of the AF is a structural substrate of hemispheric language dominance. We found consistent connections between fMRI activations and terminations of the eight WM fascicles, providing a detailed description of the language connectome. WM fascicle terminations were also observed beyond fMRI-confirmed language areas and reached numerous cortical areas involved in different functional brain networks. These findings suggest that the reported WM fascicles are not exclusively involved in language and might be related to other cognitive functions such as visual recognition, spatial attention, executive functions, memory, and processing of emotional and behavioral aspects.

Show MeSH