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Segmentation of the inferior longitudinal fasciculus in the human brain: A white matter dissection and diffusion tensor tractography study.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, Radiology.
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2017 (English)In: Brain Research, ISSN 0006-8993, E-ISSN 1872-6240, no 1675, 102-115 p., S0006-8993(17)30386-4Article in journal (Refereed) Published
Abstract [en]

The inferior longitudinal fascicle (ILF) is one of the major occipital-temporal association pathways. Several studies have mapped its hierarchical segmentation to specific functions. There is, however, no consensus regarding a detailed description of ILF fibre organisation. The aim of this study was to establish whether the ILF has a constant number of subcomponents. A secondary aim was to determine the quantitative diffusion proprieties of each subcomponent and assess their anatomical trajectories and connectivity patterns. A white matter dissection of 14 post-mortem normal human hemispheres was conducted to define the course of the ILF and its subcomponents. These anatomical results were then investigated in 24 right-handed, healthy volunteers using in vivo diffusion tensor imaging (DTI) and streamline tractography. Fractional anisotropy (FA), volume, fibre length and the symmetry coefficient of each fibre group were analysed. In order to show the connectivity pattern of the ILF, we also conducted an analysis of the cortical terminations of each segment. We confirmed that the main structure of the ILF is composed of three constant components reflecting the occipital terminations: the fusiform, the lingual and the dorsolateral-occipital. ILF volume was significantly lateralised to the right. The examined indices of ILF subcomponents did not show any significant difference in lateralisation. The connectivity pattern and the quantitative distribution of ILF subcomponents suggest a pivotal role for this bundle in integrating information from highly specialised modular visual areas with activity in anterior temporal territory, which has been previously shown to be important for memory and emotions.

Place, publisher, year, edition, pages
2017. no 1675, 102-115 p., S0006-8993(17)30386-4
Keyword [en]
DTT, ILF, Occipital-temporal connectivity, Social cognition, Visual memory, White matter
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-329751DOI: 10.1016/j.brainres.2017.09.005PubMedID: 28899757OAI: oai:DiVA.org:uu-329751DiVA: diva2:1142849
Available from: 2017-09-20 Created: 2017-09-20 Last updated: 2017-10-30
In thesis
1. Diffusion tensor magnetic resonance imaging of the brain: Tractography analysis with application in healthy individuals and patients
Open this publication in new window or tab >>Diffusion tensor magnetic resonance imaging of the brain: Tractography analysis with application in healthy individuals and patients
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In study 1, thirty-eight healthy controls were used for optimization of the method. Fifteen patients with progressive supranuclear palsy and an equal number of age-matched healthy controls underwent diffusion tensor MRI and were then investigated and compared groupwise.

It was shown that tractography analyses may preferably be performed regionally, such as along the tracts or in different segments of the tracts. Normalization of white matter tracts can be performed using anatomical landmarks.

In study 2, 104 males and 153 females in the age interval 13 to 84 years of age participated as healthy individuals in order to investigate age-related changes with diffusion tensor MRI.

It was shown that spatially differences in age-related changes exist between subdivided segments within white matter tracts. The aging processes within the CB and the IFO vary regionally.

In study 3, 38 human brains were used for investigation of the white matter tract inferior longitudinal fasciculus (ILF) and its subcomponents. Of these, white matter anatomical dissection was performed in 14 post-mortem normal human brains. The remaining 24 brains were investigated in vivo with diffusion tensor MRI in healthy individuals.

It was validated that fibers of the ILF in the occipito-temporal region have a clear, constant and detailed organisation. The anatomical connectivity pattern, and quantitative differences between the ILF subcomponents, confirmed a pivotal role of the ILF.

In study 4, 12 patients with iNPH were included in the study and examined with diffusion tensor at three time points. For comparison, 12 healthy controls, matched by gender and age were also included. Controls were examined with MRI only once.

It was shown that DTI measures differ significantly between patients with iNPH and healthy controls. DTI measures of the CC, the CST and the SLF, correlated to changes in clinical symptoms after shunt surgery.

Deeper knowledge about functions of the brain increases possibilities to take advantages from DTI analyses with tractography. 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 62 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1394
Keyword
Magnetic Resonance Imaging, Diffusion Tensor Imaging, Tractography, white matter tracts
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Radiology
Identifiers
urn:nbn:se:uu:diva-332596 (URN)978-91-513-0147-1 (ISBN)
Public defence
2017-12-20, Gustavianum, Auditorium Minus, Akademigatan 3, Uppsala, 09:15 (English)
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Available from: 2017-11-29 Created: 2017-10-30 Last updated: 2017-11-29

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