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Inferior longitudinal fasciculus

About: Inferior longitudinal fasciculus is a research topic. Over the lifetime, 470 publications have been published within this topic receiving 23420 citations.


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Journal ArticleDOI
TL;DR: The anatomical findings are relevant to the evolution of language, provide a framework for Lichtheim's symptom‐based neurological model of aphasia, and constrain, anatomically, contemporary connectionist accounts of language.
Abstract: Early anatomically based models of language consisted of an arcuate tract connecting Broca's speech and Wernicke's comprehension centers; a lesion of the tract resulted in conduction aphasia. However, the heterogeneous clinical presentations of conduction aphasia suggest a greater complexity of perisylvian anatomical connections than allowed for in the classical anatomical model. This article re-explores perisylvian language connectivity using in vivo diffusion tensor magnetic resonance imaging tractography. Diffusion tensor magnetic resonance imaging data from 11 right-handed healthy male subjects were averaged, and the arcuate fasciculus of the left hemisphere reconstructed from this data using an interactive dissection technique. Beyond the classical arcuate pathway connecting Broca's and Wernicke's areas directly, we show a previously undescribed, indirect pathway passing through inferior parietal cortex. The indirect pathway runs parallel and lateral to the classical arcuate fasciculus and is composed of an anterior segment connecting Broca's territory with the inferior parietal lobe and a posterior segment connecting the inferior parietal lobe to Wernicke's territory. This model of two parallel pathways helps explain the diverse clinical presentations of conduction aphasia. The anatomical findings are also relevant to the evolution of language, provide a framework for Lichtheim's symptom-based neurological model of aphasia, and constrain, anatomically, contemporary connectionist accounts of language. Ann Neurol 2005

1,653 citations

Journal ArticleDOI
TL;DR: The use of diffusion tensor magnetic resonance tractography to visualize the three-dimensional structure of the major white matter fasciculi within living human brain adds a new dimension to anatomical descriptions of the living humanbrain.

1,604 citations

Journal ArticleDOI
01 Mar 2007-Brain
TL;DR: By replicating the major features of these tracts identified by histological techniques in monkey, it is shown that DSI has the potential to cast new light on the organization of the human brain in the normal state and in clinical disorders.
Abstract: 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.

1,014 citations

Journal ArticleDOI
01 Sep 2003-Brain
TL;DR: The results suggest that a major associative connection between the occipital and anterior temporal lobe is provided by a fibre bundle whose origin, course and termination are consistent with classical descriptions of the ILF in man and with monkey visual anatomy.
Abstract: Diffusion tensor MRI (DT‐MRI) provides information about the structural organization and orientation of white matter fibres and, through the technique of ‘tractography’, reveals the trajectories of cerebral white matter tracts. We used tractography in the living human brain to address the disputed issue of the nature of occipital and temporal connections. Classical anatomical studies described direct fibre connections between occipital and anterior temporal cortex in a bundle labelled the inferior longitudinal fasciculus (ILF). However, their presence has been challenged by more recent evidence suggesting that connections between the two regions are entirely indirect, conveyed by the occipito‐temporal projection system—a chain of U‐shaped association fibres. DT‐MRI data were collected from 11 right‐handed healthy subjects (mean age 33.3 ± 4.7 years). Each data set was co‐registered with a standard MRI brain template, and a group‐averaged DT‐MRI data set was created. ‘Virtual’ in vivo dissection of occipito‐temporal connections was performed in the group‐averaged data. Further detailed virtual dissection was performed on the single brain data sets. Our results suggest that in addition to the indirect connections of the occipito‐temporal projection system: (i) a major associative connection between the occipital and anterior temporal lobe is provided by a fibre bundle whose origin, course and termination are consistent with classical descriptions of the ILF in man and with monkey visual anatomy; (ii) the tractography‐defined ILF is structurally distinct from fibres of the optic radiation and from U‐shaped fibres connecting adjacent gyri; (iii) it arises in extrastriate visual ‘association’ areas; and (iv) it projects to lateral and medial anterior temporal regions. While the function of the direct ILF pathway is unclear, it appears to mediate the fast transfer of visual signals to anterior temporal regions and neuromodulatory back‐projections from the amygdala to early visual areas. Future tractography studies of patients with occipito‐temporal disconnection syndromes may help define the functional roles of the direct and indirect occipito‐temporal pathways.

891 citations

Journal ArticleDOI
TL;DR: Simulations show that the deflection term is less sensitive than the major eigenvector to image noise and is promising for mapping the organizational patterns of white matter in the human brain as well as mapping the relationship between major fiber trajectories and the location and extent of brain lesions.
Abstract: Diffusion tensor MRI provides unique directional diffusion information that can be used to estimate the patterns of white matter connectivity in the human brain. In this study, the behavior of an algorithm for white matter tractography is examined. The algorithm, called TEND, uses the entire diffusion tensor to deflect the estimated fiber trajectory. Simulations and imaging experiments on in vivo human brains were performed to investigate the behavior of the tractography algorithm. The simulations show that the deflection term is less sensitive than the major eigenvector to image noise. In the human brain imaging experiments, estimated tracts were generated in corpus callosum, corticospinal tract, internal capsule, corona radiata, superior longitudinal fasciculus, inferior longitudinal fasciculus, fronto-occipital fasciculus, and uncinate fasciculus. This approach is promising for mapping the organizational patterns of white matter in the human brain as well as mapping the relationship between major fiber trajectories and the location and extent of brain lesions. Hum. Brain Mapping 18:306 -321, 2003. © 2003 Wiley-Liss, Inc.

614 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202330
202270
202145
202051
201929
201838