Occipital White Matter Tracts in Human and Macaque
Hiromasa TakemuraFranco PestilliKevin S. WeinerGeorgios A. KelirisSofia M. LandiJulia SliwaFrank Q. YeMichael BarnettDavid A. LeopoldWinrich A. FreiwaldNikos K. LogothetisBrian A. Wandell
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Abstract:
We compare several major white-matter tracts in human and macaque occipital lobe using diffusion magnetic resonance imaging. The comparison suggests similarities but also significant differences in the tracts. There are several apparently homologous tracts in the 2 species, including the vertical occipital fasciculus (VOF), optic radiation, forceps major, and inferior longitudinal fasciculus (ILF). There is one large human tract, the inferior fronto-occipital fasciculus, with no corresponding fasciculus in macaque. We could identify the macaque VOF (mVOF), which has been little studied. Its position is consistent with classical invasive anatomical studies by Wernicke. VOF homology is supported by similarity of the endpoints in V3A and ventral V4 across species. The mVOF fibers intertwine with the dorsal segment of the ILF, but the human VOF appears to be lateral to the ILF. These similarities and differences between the occipital lobe tracts will be useful in establishing which circuitry in the macaque can serve as an accurate model for human visual cortex.Keywords:
Inferior longitudinal fasciculus
Fasciculus
Occipital lobe
Uncinate fasciculus
Arcuate fasciculus
Optic radiation
Arcuate fasciculus
Uncinate fasciculus
Fasciculus
Inferior longitudinal fasciculus
Superior longitudinal fasciculus
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Uncinate fasciculus
Fasciculus
Inferior longitudinal fasciculus
Arcuate fasciculus
Cingulum (brain)
Superior longitudinal fasciculus
Medial longitudinal fasciculus
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Categorization is the mental operation by which the brain classifies objects and events. It is classically assessed using semantic and non-semantic matching or sorting tasks. These tasks show a high variability in performance across healthy controls and the cerebral bases supporting this variability remain unknown. In this study we performed a voxel-based morphometry study to explore the relationships between semantic and shape categorization tasks and brain morphometric differences in 50 controls. We found significant correlation between categorization performance and the volume of the gray matter in the right anterior middle and inferior temporal gyri. Semantic categorization tasks were associated with more rostral temporal regions than shape categorization tasks. A significant relationship was also shown between white matter volume in the right temporal lobe and performance in the semantic tasks. Tractography revealed that this white matter region involved several projection and association fibers, including the arcuate fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and inferior longitudinal fasciculus. These results suggest that categorization abilities are supported by the anterior portion of the right temporal lobe and its interaction with other areas.
Uncinate fasciculus
Arcuate fasciculus
Inferior longitudinal fasciculus
Fasciculus
Superior longitudinal fasciculus
Voxel-based morphometry
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Arcuate fasciculus
Inferior longitudinal fasciculus
Uncinate fasciculus
Fasciculus
Superior longitudinal fasciculus
Inferior temporal gyrus
Corticospinal tract
Human Connectome Project
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Background. Despite progress made in understanding functional reorganization patterns underlying recovery in subacute aphasia, the relation between recovery and changes in white matter structure remains unclear. Objective. To investigate changes in dorsal and ventral language white matter tract integrity in relation to naming recovery in subacute poststroke aphasia. Methods. Ten participants with aphasia after left-hemisphere stroke underwent language testing and diffusion tensor imaging twice within 3 months post onset, with a 1-month interval between sessions. Deterministic tractography was used to bilaterally reconstruct the superior longitudinal fasciculus (SLF), inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), middle longitudinal fasciculus (MdLF), and uncinate fasciculus (UF). Per tract, the mean fractional anisotropy (FA) was extracted as a measure of microstructural integrity. Naming accuracy was assessed with the Boston Naming Test (BNT). Correlational analyses were performed to investigate the relationship between changes in FA values and change in BNT score. Results. A strong positive correlation was found between FA change in the right ILF within the ventral stream and change on the BNT ( r = 0.91, P < .001). An increase in FA in the right ILF was associated with considerable improvement of naming accuracy (range BNT change score: 12-14), a reduction with limited improvement or slight deterioration. No significant correlations were found between change in naming accuracy and FA change in any of the other right or left ventral and dorsal language tracts. Conclusions. Naming recovery in subacute aphasia is associated with change in the integrity of the right ILF.
Fasciculus
Inferior longitudinal fasciculus
Uncinate fasciculus
Arcuate fasciculus
Superior longitudinal fasciculus
Boston Naming Test
Corticospinal tract
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The anatomic localization of brain functions can be characterized via diffusion tensor imaging in patients with brain tumors and neurological symptoms. The goal of the present study was to evaluate the function of the ventral, arcuate fasciculus (AF) and the superior longitudinal fasciculus (SLF)-related language pathways using these techniques by analyzing 9 patients treated in our hospital between 2007 and 2011. In cases 1–3, the left ventral pathways, namely, the inferior longitudinal fasciculus, uncinate fasciculus or inferior fronto-occipital fasciculus, were mainly damaged, and the common dysfunction experienced by these patients was a deficit in object naming. In cases 4–6, the left SLF was mainly damaged, and the common deficit was dysgraphia. In cases 7–9, the left AF was mainly damaged, and almost all language functions related to phonology were abnormal. These results suggest that the left ventral, AF and SLF-related pathways are closely related to visual, auditory and hand-related language function, respectively.
Fasciculus
Arcuate fasciculus
Inferior longitudinal fasciculus
Medial longitudinal fasciculus
Superior longitudinal fasciculus
Uncinate fasciculus
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To propose a clinically practical and simple fiber tracking method for language pathways, and to explore its feasibility in preoperative planning for brain tumors adjacent to the language cortex.Diffusion tensor imaging was examined in 18 healthy subjects and 13 patients with brain tumors adjacent to the language cortex between December 2013 and June 2014. The associated fibers of language pathways were reconstructed using a commercial software (Syngo workstation). Firstly, the feasibility of fiber tracking method for language pathways in healthy subjects were studied, and then its application was assessed in patients with brain tumors. The anatomic relationship between tumors and the associated fibers was analyzed.By selecting appropriate regions of interest, the associated fibers in the dorsal pathways (superior longitudinal fasciculus/arcuate fasciculus, including both direct and indirect pathways) and ventral pathways (uncinate fasciculus, middle longitudinal fasciculus, inferior longitudinal fasciculus and inferiorfronto-occipital fasciculus) were reconstructed in all 18 healthy subjects. In patients with brain tumors, the relationship between the tumors and adjacent associated fibers were divided into two types: adjacent associated fibers could be displaced or separated, and involved the superior longitudinal fasciculus/arcuate fasciculus (n=6), middle longitudinal fasciculus (n=4), uncinate fasciculus (n=3), inferior longitudinal fasciculus (n=3) and inferiorfronto-occipital fasciculus (n=2); alternatively, the adjacent associated fibers were infiltrated or destroyed, and involved the inferiorfronto-occipital fasciculus (n=10), uncinate fasciculus (n=8), middle longitudinal fasciculus (n=5), inferior longitudinal fasciculus (n=4) and superior longitudinal fasciculus/arcuate fasciculus (n=3).The associated fibers of language pathways could be visualized rapidly and in real-time by fiber tracking technology based on diffusion tensor imaging. This is feasible for preoperative planning regarding brain tumors adjacent to the language cortex.
Fasciculus
Arcuate fasciculus
Medial longitudinal fasciculus
Inferior longitudinal fasciculus
Uncinate fasciculus
Superior longitudinal fasciculus
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Much is known about the role of cortical areas in language processing. The shift towards network approaches in recent years has highlighted the importance of uncovering the role of white matter in connecting these areas. However, despite a large body of research, many of these tracts' functions are not well-understood. We present a comprehensive review of the empirical evidence on the role of eight major tracts that are hypothesized to be involved in language processing (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, extreme capsule, middle longitudinal fasciculus, superior longitudinal fasciculus, arcuate fasciculus, and frontal aslant tract). For each tract, we hypothesize its role based on the function of the cortical regions it connects. We then evaluate these hypotheses with data from three sources: studies in neurotypical individuals, neuropsychological data, and intraoperative stimulation studies. Finally, we summarize the conclusions supported by the data and highlight the areas needing further investigation.
Arcuate fasciculus
Uncinate fasciculus
Fasciculus
Inferior longitudinal fasciculus
Superior longitudinal fasciculus
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Arcuate fasciculus
Uncinate fasciculus
Angelman Syndrome
Fasciculus
Inferior longitudinal fasciculus
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Citations (58)
Much is known about the role of various cortical areas in language production and comprehension. The shift towards network approaches in recent years has highlighted the importance of uncovering the role of the white matter in connecting these areas. However, despite a relatively large body of research, the function of many of these tracts is still underdefined. In this paper, we present a comprehensive review of the empirical evidence on the role of eight major tracts that are hypothesized to be involved in language processing (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, the extreme capsule, middle longitudinal fasciculus, superior longitudinal fasciculus, arcuate fasciculus and frontal aslant tract). For each tract, we hypothesize the tract’s role based on the function of the cortical regions it connects. We then evaluate these hypotheses in light of data from three sources: studies in neurotypical individuals, neuropsychological data, and intraoperative stimulation studies. Finally, we summarize the conclusions supported by the data and highlight the areas in need of further investigation.
Arcuate fasciculus
Uncinate fasciculus
Fasciculus
Inferior longitudinal fasciculus
Superior longitudinal fasciculus
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Citations (1)