The Experts below are selected from a list of 1002 Experts worldwide ranked by ideXlab platform
Deepak N. Pandya - One of the best experts on this subject based on the ideXlab platform.
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distinct parietal and temporal pathways to the homologues of broca s area in the monkey
PLOS Biology, 2009Co-Authors: Michael Petrides, Deepak N. PandyaAbstract:The homologues of the two distinct architectonic areas 44 and 45 that constitute the anterior language zone (Broca's region) in the human ventrolateral frontal lobe were recently established in the macaque monkey. Although we know that the inferior parietal lobule and the lateral temporal cortical region project to the ventrolateral frontal cortex, we do not know which of the several cortical areas found in those regions project to the homologues of Broca's region in the macaque monkey and by means of which white matter pathways. We have used the autoradiographic method, which permits the establishment of the cortical area from which axons originate (i.e., the site of injection), the precise course of the axons in the white matter, and their termination within particular cortical areas, to examine the parietal and temporal connections to area 44 and the two subdivisions of area 45 (i.e., areas 45A and 45B). The results demonstrated a ventral temporo-frontal stream of fibers that originate from various auditory, multisensory, and visual association cortical areas in the intermediate superolateral temporal region. These axons course via the Extreme Capsule and target most strongly area 45 with a more modest termination in area 44. By contrast, a dorsal stream of axons that originate from various cortical areas in the inferior parietal lobule and the adjacent caudal superior temporal sulcus was found to target both areas 44 and 45. These axons course in the superior longitudinal fasciculus, with some axons originating from the ventral inferior parietal lobule and the adjacent superior temporal sulcus arching and forming a simple arcuate fasciculus. The cortex of the most rostral part of the inferior parietal lobule is preferentially linked with the ventral premotor cortex (ventral area 6) that controls the orofacial musculature. The cortex of the intermediate part of the inferior parietal lobule is linked with both areas 44 and 45. These findings demonstrate the posterior parietal and temporal connections of the ventrolateral frontal areas, which, in the left hemisphere of the human brain, were adapted for various aspects of language production. These precursor circuits that are found in the nonlinguistic, nonhuman, primate brain also exist in the human brain. The possible reasons why these areas were adapted for language use in the human brain are discussed. The results throw new light on the prelinguistic precursor circuitry of Broca's region and help understand functional interactions between Broca's ventrolateral frontal region and posterior parietal and temporal association areas.
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The Extreme Capsule in humans and rethinking of the language circuitry
Brain Structure and Function, 2008Co-Authors: Nikos Makris, Deepak N. PandyaAbstract:Experimental and imaging studies in monkeys have outlined various long association fiber pathways within the fronto-temporo-parietal region. In the present study, the trajectory of the Extreme Capsule (EmC) fibers has been delineated in five human subjects using DT-MRI tractography. The EmC seems to be a long association fiber pathway, which courses between the inferior frontal region and the superior temporal gyrus extending into the inferior parietal lobule. Comparison of EmC fibers with the adjacent association fiber pathway, the middle longitudinal fascicle (MdLF), in the same subjects reveals that EmC is located in a medial and rostral position relative to MdLF flanking in part the medial wall of the insula. The EmC can also be differentiated from other neighboring fiber pathways such as the external Capsule, uncinate fascicle, arcuate fascicle, superior longitudinal fascicles II and III, and the inferior longitudinal fascicle. Given the location of EmC within the language zone, specifically Broca’s area in the frontal lobe, and Wernicke’s area in the temporal lobe and inferior parietal lobule, it is suggested that the Extreme Capsule could have a role in language function.
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efferent association pathways from the rostral prefrontal cortex in the macaque monkey
The Journal of Neuroscience, 2007Co-Authors: Michael Petrides, Deepak N. PandyaAbstract:The different prefrontal cortical regions exert executive control over processing occurring in posterior cortical regions. We examined with the autoradiographic method, in the macaque monkey, the course and terminations of the efferent corticocortical connections of the rostral prefrontal region, the function of which is least understood. Three efferent streams of fibers organized into three distinct fasciculi convey rostral prefrontal influences on posterior cortical areas. These connections provide powerful insights into the cortical regions on which executive control is being exercised. The lateral stream of fibers via the Extreme Capsule targets the midsection of the auditory superior temporal region and the multisensory areas of the superior temporal sulcus, thus permitting control over the most integrated aspects of cognitive processing. The fibers coursing through the Extreme Capsule originating in areas 10 and 9 continue as part of the white matter of the superior temporal gyrus (i.e., the middle longitudinal fasciculus) to target the midportion of the superior temporal gyrus (areas TAa, TS2, and TS3) and adjacent multisensory area TPO within the upper bank of the superior temporal sulcus. Some of the fibers from areas 10 and 9 that enter the Extreme Capsule terminate in the ventral part of the insula. The dorsomedial limbic stream via the cingulate fasciculus targets the anterior and posterior cingulate cortex, as well as the retrosplenial cortex, allowing control over motivational and memory processes. A ventral limbic stream via the uncinate fasciculus targets the temporal proisocortex and the amygdala, indicating an additional powerful influence over the emotional motivational sphere.
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association fibre pathways of the brain parallel observations from diffusion spectrum imaging and autoradiography
Brain, 2007Co-Authors: Jeremy D Schmahmann, Deepak N. Pandya, Ruopeng Wang, Helen E Darceuil, Alex J De Crespigny, Van J WedeenAbstract:Understanding the long association pathways that convey cortical connections is a critical step in exploring the anatomic substrates of cognition in health and disease. Diffusion tensor imaging (DTI) is able to demonstrate fibre tracts non-invasively, but present approaches have been hampered by the inability to visualize fibres that have intersecting trajectories (crossing fibres), and by the lack of a detailed map of the origins, course and terminations of the white matter pathways. We therefore used diffusion spectrum imaging (DSI) that has the ability to resolve crossing fibres at the scale of single MRI voxels, and identified the long association tracts in the monkey brain. We then compared the results with available expositions of white matter pathways in the monkey using autoradiographic histological tract tracing. We identified 10 long association fibre bundles with DSI that match the observations in the isotope material: emanating from the parietal lobe, the superior longitudinal fasciculus subcomponents I, II and III; from the occipital-parietal region, the fronto-occipital fasciculus; from the temporal lobe, the middle longitudinal fasciculus and from rostral to caudal, the uncinate fasciculus, Extreme Capsule and arcuate fasciculus; from the occipital-temporal region, the inferior longitudinal fasciculus; and from the cingulate gyrus, the cingulum bundle. We suggest new interpretations of the putative functions of these fibre bundles based on the cortical areas that they link. These findings using DSI and validated with reference to autoradiographic tract tracing in the monkey represent a considerable advance in the understanding of the fibre pathways in the cerebral white matter. By replicating the major features of these tracts identified by histological techniques in monkey, we show that DSI has the potential to cast new light on the organization of the human brain in the normal state and in clinical disorders.
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efferent association pathways originating in the caudal prefrontal cortex in the macaque monkey
The Journal of Comparative Neurology, 2006Co-Authors: Deepak N. Pandya, M PetridesAbstract:The efferent association fibers from the caudal part of the prefrontal cortex to posterior cortical areas course via several pathways: the three components of the superior longitudinal fasciculus (SLF I, SLF II, and SLF III), the arcuate fasciculus (AF), the fronto-occipital fasciculus (FOF), the cingulate fasciculus (CING F), and the Extreme Capsule (Extm C). Fibers from area 8Av course via FOF and SLF II, merging in the white matter of the inferior parietal lobule (IPL) and terminating in the caudal intraparietal sulcus (IPS). A group of these fibers turns ventrally to terminate in the caudal superior temporal sulcus (STS). Fibers from the rostral part of area 8Ad course via FOF and SLF II to the IPS and IPL and via the AF to the caudal superior temporal gyrus and STS. Some fibers from the rostral part of area 8Ad are conveyed to the medial parieto-occipital region via FOF, to the STS via Extm C, and to the caudal cingulate gyrus via CING F. Fibers from area 8B travel via SLF I to the supplementary motor area and area 31 in the caudal dorsal cingulate region and via the CING F to cingulate areas 24 and 23 and the cingulate motor areas. Fibers from area 9/46d course via SLF I to the superior parietal lobule and medial parieto-occipital region, via SLF II to the IPL. Fibers from area 9/46v travel via SLF III to the rostral IPL and the frontoparietal opercular region and via the CING F to the cingulate gyrus.
Dorothee Saur - One of the best experts on this subject based on the ideXlab platform.
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fronto parietal dorsal and ventral pathways in the context of different linguistic manipulations
Brain and Language, 2013Co-Authors: Philipp Kellmeyer, Cornelius Weiller, Wolfram Ziegler, Claudia Peschke, Eisenberger Juliane, Susanne Schnell, Annette Baumgaertner, Dorothee SaurAbstract:This study investigates structural connectivity between left fronto-parietal brain regions that were identified in a previous fMRI study which used different linguistic manipulation tasks. Diffusion-weighted images were acquired from 20 volunteers. Structural connectivity between brain regions from the fMRI study was computed using probabilistic fiber tracking. For suprasegmental manipulation, left inferior parietal lobule (IPL) and left inferior frontal gyrus (IFG), pars opercularis, were connected by a dorsal pathway via the arcuate fascicle and superior longitudinal fascicle III. For segmental manipulation, left IPL and IFG, pars triangularis, were connected by a ventral pathway via the middle longitudinal fascicle and the Extreme Capsule. We conclude that the dorsal pathway provides a route for mapping from phonological memory in IPL to the inferior frontal articulatory network while the ventral pathway could facilitate the modulation of phonological units based on lexical-semantic aspects, mediate the complexity of auditory objects and the unification of actor-event schemata.
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damage to ventral and dorsal language pathways in acute aphasia
Brain, 2013Co-Authors: Dorothee Kummerer, Hans-otto Karnath, Volkmar Glauche, Cornelius Weiller, Philipp Kellmeyer, Gesa Hartwigsen, Irina Mader, Stefan Kloppel, Julia Suchan, Dorothee SaurAbstract:Converging evidence from neuroimaging studies and computational modelling suggests an organization of language in a dual dorsal-ventral brain network: a dorsal stream connects temporoparietal with frontal premotor regions through the superior longitudinal and arcuate fasciculus and integrates sensorimotor processing, e.g. in repetition of speech. A ventral stream connects temporal and prefrontal regions via the Extreme Capsule and mediates meaning, e.g. in auditory comprehension. The aim of our study was to test, in a large sample of 100 aphasic stroke patients, how well acute impairments of repetition and comprehension correlate with lesions of either the dorsal or ventral stream. We combined voxelwise lesion-behaviour mapping with the dorsal and ventral white matter fibre tracts determined by probabilistic fibre tracking in our previous study in healthy subjects. We found that repetition impairments were mainly associated with lesions located in the posterior temporoparietal region with a statistical lesion maximum in the periventricular white matter in projection of the dorsal superior longitudinal and arcuate fasciculus. In contrast, lesions associated with comprehension deficits were found more ventral-anterior in the temporoprefrontal region with a statistical lesion maximum between the insular cortex and the putamen in projection of the ventral Extreme Capsule. Individual lesion overlap with the dorsal fibre tract showed a significant negative correlation with repetition performance, whereas lesion overlap with the ventral fibre tract revealed a significant negative correlation with comprehension performance. To summarize, our results from patients with acute stroke lesions support the claim that language is organized along two segregated dorsal-ventral streams. Particularly, this is the first lesion study demonstrating that task performance on auditory comprehension measures requires an interaction between temporal and prefrontal brain regions via the ventral Extreme Capsule pathway.
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reply to yamada the Extreme Capsule is the ventral pathway for language
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Dorothee Saur, Philipp Kellmeyer, Cornelius WeillerAbstract:In his letter (1), Yamada claims that, in our article (2), we erroneously allocated the ventral pathway for language processing to the Extreme Capsule (EmC) rather than the external Capsule (EC). He argues that, in his data (3), the direction of fibers running in the EmC “is not anteroposterior but rather transverse or superoinferior in the transaxial plane.” Instead, the EC has fibers running in the “anteroposterior direction,” thereby providing the temporo-frontal connection of interest.
Cornelius Weiller - One of the best experts on this subject based on the ideXlab platform.
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the Extreme Capsule and aphasia proof of concept of a new way relating structure to neurological symptoms
Brain communications, 2021Co-Authors: Ariane Martinez Oeckel, Michel Rijntjes, Volkmar Glauche, Dorothee Kummerer, Christoph P Kaller, Karl Egger, Cornelius WeillerAbstract:We present anatomy-based symptom-lesion mapping to assess the association between lesions of tracts in the Extreme Capsule and aphasia. The study cohort consisted of 123 patients with acute left-hemispheric stroke without a lesion of language-related cortical areas of the Stanford atlas of functional regions of interest. On templates generated through global fibre tractography, lesions of the Extreme Capsule and of the arcuate fascicle were quantified and correlated with the occurrence of aphasia (n = 18) as defined by the Token Test. More than 15% damage of the slice plane through the Extreme Capsule was a strong independent predictor of aphasia in stroke patients, odds ratio 16.37, 95% confidence interval: 3.11-86.16, P 15% in the arcuate fascicle were not associated with aphasia. Our results support the relevance of a ventral pathway in the language network running through the Extreme Capsule.
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fronto parietal dorsal and ventral pathways in the context of different linguistic manipulations
Brain and Language, 2013Co-Authors: Philipp Kellmeyer, Cornelius Weiller, Wolfram Ziegler, Claudia Peschke, Eisenberger Juliane, Susanne Schnell, Annette Baumgaertner, Dorothee SaurAbstract:This study investigates structural connectivity between left fronto-parietal brain regions that were identified in a previous fMRI study which used different linguistic manipulation tasks. Diffusion-weighted images were acquired from 20 volunteers. Structural connectivity between brain regions from the fMRI study was computed using probabilistic fiber tracking. For suprasegmental manipulation, left inferior parietal lobule (IPL) and left inferior frontal gyrus (IFG), pars opercularis, were connected by a dorsal pathway via the arcuate fascicle and superior longitudinal fascicle III. For segmental manipulation, left IPL and IFG, pars triangularis, were connected by a ventral pathway via the middle longitudinal fascicle and the Extreme Capsule. We conclude that the dorsal pathway provides a route for mapping from phonological memory in IPL to the inferior frontal articulatory network while the ventral pathway could facilitate the modulation of phonological units based on lexical-semantic aspects, mediate the complexity of auditory objects and the unification of actor-event schemata.
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damage to ventral and dorsal language pathways in acute aphasia
Brain, 2013Co-Authors: Dorothee Kummerer, Hans-otto Karnath, Volkmar Glauche, Cornelius Weiller, Philipp Kellmeyer, Gesa Hartwigsen, Irina Mader, Stefan Kloppel, Julia Suchan, Dorothee SaurAbstract:Converging evidence from neuroimaging studies and computational modelling suggests an organization of language in a dual dorsal-ventral brain network: a dorsal stream connects temporoparietal with frontal premotor regions through the superior longitudinal and arcuate fasciculus and integrates sensorimotor processing, e.g. in repetition of speech. A ventral stream connects temporal and prefrontal regions via the Extreme Capsule and mediates meaning, e.g. in auditory comprehension. The aim of our study was to test, in a large sample of 100 aphasic stroke patients, how well acute impairments of repetition and comprehension correlate with lesions of either the dorsal or ventral stream. We combined voxelwise lesion-behaviour mapping with the dorsal and ventral white matter fibre tracts determined by probabilistic fibre tracking in our previous study in healthy subjects. We found that repetition impairments were mainly associated with lesions located in the posterior temporoparietal region with a statistical lesion maximum in the periventricular white matter in projection of the dorsal superior longitudinal and arcuate fasciculus. In contrast, lesions associated with comprehension deficits were found more ventral-anterior in the temporoprefrontal region with a statistical lesion maximum between the insular cortex and the putamen in projection of the ventral Extreme Capsule. Individual lesion overlap with the dorsal fibre tract showed a significant negative correlation with repetition performance, whereas lesion overlap with the ventral fibre tract revealed a significant negative correlation with comprehension performance. To summarize, our results from patients with acute stroke lesions support the claim that language is organized along two segregated dorsal-ventral streams. Particularly, this is the first lesion study demonstrating that task performance on auditory comprehension measures requires an interaction between temporal and prefrontal brain regions via the ventral Extreme Capsule pathway.
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reply to yamada the Extreme Capsule is the ventral pathway for language
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Dorothee Saur, Philipp Kellmeyer, Cornelius WeillerAbstract:In his letter (1), Yamada claims that, in our article (2), we erroneously allocated the ventral pathway for language processing to the Extreme Capsule (EmC) rather than the external Capsule (EC). He argues that, in his data (3), the direction of fibers running in the EmC “is not anteroposterior but rather transverse or superoinferior in the transaxial plane.” Instead, the EC has fibers running in the “anteroposterior direction,” thereby providing the temporo-frontal connection of interest.
Robin I. M. Dunbar - One of the best experts on this subject based on the ideXlab platform.
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The Extreme Capsule fiber complex in humans and macaque monkeys: a comparative diffusion MRI tractography study
Brain Structure and Function, 2016Co-Authors: Rogier B. Mars, Sean Foxley, Lennart Verhagen, Saad Jbabdi, Jérôme Sallet, Maryann P. Noonan, Franz-xaver Neubert, Jesper L. Andersson, Paula L. Croxson, Robin I. M. DunbarAbstract:We compared the course and cortical projections of white matter fibers passing through the Extreme Capsule in humans and macaques. Previous comparisons of this tract have suggested a uniquely human posterior projection, but these studies have always employed different techniques in the different species. Here we used the same technique, diffusion MRI, in both species to avoid attributing differences in techniques to differences in species. Diffusion MRI-based probabilistic tractography was performed from a seed area in the Extreme Capsule in both human and macaques. We compared in vivo data of humans and macaques as well as one high-resolution ex vivo macaque dataset. Tractography in the macaque was able to replicate most results known from macaque tracer studies, including selective innervation of frontal cortical areas and targets in the superior temporal cortex. In addition, however, we also observed some tracts that are not commonly reported in macaque tracer studies and that are more reminiscent of results previously only reported in the human. In humans, we show that the ventrolateral prefrontal cortex innervations are broadly similar to those in the macaque. These results suggest that evolutionary changes in the human Extreme Capsule fiber complex are likely more gradual than punctuated. Further, they demonstrate both the potential and limitations of diffusion MRI tractography.
Philipp Kellmeyer - One of the best experts on this subject based on the ideXlab platform.
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fronto parietal dorsal and ventral pathways in the context of different linguistic manipulations
Brain and Language, 2013Co-Authors: Philipp Kellmeyer, Cornelius Weiller, Wolfram Ziegler, Claudia Peschke, Eisenberger Juliane, Susanne Schnell, Annette Baumgaertner, Dorothee SaurAbstract:This study investigates structural connectivity between left fronto-parietal brain regions that were identified in a previous fMRI study which used different linguistic manipulation tasks. Diffusion-weighted images were acquired from 20 volunteers. Structural connectivity between brain regions from the fMRI study was computed using probabilistic fiber tracking. For suprasegmental manipulation, left inferior parietal lobule (IPL) and left inferior frontal gyrus (IFG), pars opercularis, were connected by a dorsal pathway via the arcuate fascicle and superior longitudinal fascicle III. For segmental manipulation, left IPL and IFG, pars triangularis, were connected by a ventral pathway via the middle longitudinal fascicle and the Extreme Capsule. We conclude that the dorsal pathway provides a route for mapping from phonological memory in IPL to the inferior frontal articulatory network while the ventral pathway could facilitate the modulation of phonological units based on lexical-semantic aspects, mediate the complexity of auditory objects and the unification of actor-event schemata.
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damage to ventral and dorsal language pathways in acute aphasia
Brain, 2013Co-Authors: Dorothee Kummerer, Hans-otto Karnath, Volkmar Glauche, Cornelius Weiller, Philipp Kellmeyer, Gesa Hartwigsen, Irina Mader, Stefan Kloppel, Julia Suchan, Dorothee SaurAbstract:Converging evidence from neuroimaging studies and computational modelling suggests an organization of language in a dual dorsal-ventral brain network: a dorsal stream connects temporoparietal with frontal premotor regions through the superior longitudinal and arcuate fasciculus and integrates sensorimotor processing, e.g. in repetition of speech. A ventral stream connects temporal and prefrontal regions via the Extreme Capsule and mediates meaning, e.g. in auditory comprehension. The aim of our study was to test, in a large sample of 100 aphasic stroke patients, how well acute impairments of repetition and comprehension correlate with lesions of either the dorsal or ventral stream. We combined voxelwise lesion-behaviour mapping with the dorsal and ventral white matter fibre tracts determined by probabilistic fibre tracking in our previous study in healthy subjects. We found that repetition impairments were mainly associated with lesions located in the posterior temporoparietal region with a statistical lesion maximum in the periventricular white matter in projection of the dorsal superior longitudinal and arcuate fasciculus. In contrast, lesions associated with comprehension deficits were found more ventral-anterior in the temporoprefrontal region with a statistical lesion maximum between the insular cortex and the putamen in projection of the ventral Extreme Capsule. Individual lesion overlap with the dorsal fibre tract showed a significant negative correlation with repetition performance, whereas lesion overlap with the ventral fibre tract revealed a significant negative correlation with comprehension performance. To summarize, our results from patients with acute stroke lesions support the claim that language is organized along two segregated dorsal-ventral streams. Particularly, this is the first lesion study demonstrating that task performance on auditory comprehension measures requires an interaction between temporal and prefrontal brain regions via the ventral Extreme Capsule pathway.
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reply to yamada the Extreme Capsule is the ventral pathway for language
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: Dorothee Saur, Philipp Kellmeyer, Cornelius WeillerAbstract:In his letter (1), Yamada claims that, in our article (2), we erroneously allocated the ventral pathway for language processing to the Extreme Capsule (EmC) rather than the external Capsule (EC). He argues that, in his data (3), the direction of fibers running in the EmC “is not anteroposterior but rather transverse or superoinferior in the transaxial plane.” Instead, the EC has fibers running in the “anteroposterior direction,” thereby providing the temporo-frontal connection of interest.
