Jones, D.K.: Studying connections in the living human brain with diffusion MRI. Cortex 44(8), 936-952

Cardiff University Brain Research Imaging Centre, School of Psychology, Cardiff University, Cardiff, Wales, UK.
Cortex (Impact Factor: 5.13). 09/2008; 44(8):936-52. DOI: 10.1016/j.cortex.2008.05.002
Source: PubMed


The purpose of this article is to explain how the random walks of water molecules undergoing diffusion in living tissue may be exploited to garner information on the white matter of the human brain and its connections. We discuss the concepts underlying diffusion-weighted (DW) imaging, and diffusion tensor imaging before exploring fibre tracking, or tractography, which aims to reconstruct the three-dimensional trajectories of white matter fibres non-invasively. The two main classes of algorithm - deterministic and probabilistic tracking - are compared and example results are presented. We then discuss methods to resolve the 'crossing fibre' issue which presents a problem when using the tensor model to characterize diffusion behaviour in complex tissue. Finally, we detail some of the issues that remain to be resolved before we can reliably characterize connections of the living human brain in vivo.

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    • "Anatomical connectivity between brain regions can be measured (or rather approximated) using diffusion magnetic resonance imaging. It delineates the likelihood of white-matter fiber bundles traced to link brain regions (Johansen-Berg and Rushworth, 2009; Jones, 2008). The number of samples reaching any voxel/vertex in the gray matter or, more frequently, the likelihood of passing through brain white matter then provides the connectivity profile of a particular voxel/vertex or node in the ROI. "
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    ABSTRACT: Regional specialization and functional integration are often viewed as two fundamental principles of human brain organization. They are closely intertwined because each functionally specialized brain region is probably characterized by a distinct set of long-range connections. This notion has prompted the quickly developing family of connectivity-based parcellation (CBP) methods in neuroimaging research. CBP assumes that there is a latent structure of parcels in a region of interest (ROI). First, connectivity strengths are computed to other parts of the brain for each voxel/vertex within the ROI. These features are then used to identify functionally distinct groups of ROI voxels/vertices. CBP enjoys increasing popularity for the in-vivo mapping of regional specialization in the human brain. Due to the requirements of different applications and datasets, CBP has diverged into a heterogeneous family of methods. This broad overview critically discusses the current state as well as the commonalities and idiosyncrasies of the main CBP methods. We target frequent concerns faced by novices and veterans to provide a reference for the investigation and review of CBP studies.
    Human Brain Mapping 01/2016; DOI:10.1002/hbm.22933 · 5.97 Impact Factor
    • "DTI is a non-invasive imaging technique sensitive to the movement of water molecules in nervous tissue (Jones, 2008). When unrestricted, water diffuses randomly, whereas it is hindered in its movement in highly organized tissue such as collections of nerve fibers composing white matter. "
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    ABSTRACT: Recent advances in neuroimaging methodologies sensitive to axonal injury have made it possible to assess in vivo the extent of traumatic brain injury (TBI) -related disruption in neural structures and their connections. The objective of this paper is to review studies examining connectivity in TBI with an emphasis on structural and functional MRI methods that have proven to be valuable in uncovering neural abnormalities associated with this condition. We review studies that have examined white matter integrity in TBI of varying etiology and levels of severity, and consider how findings at different times post-injury may inform underlying mechanisms of post-injury progression and recovery. Moreover, in light of recent advances in neuroimaging methods to study the functional connectivity among brain regions that form integrated networks, we review TBI studies that use resting-state functional connectivity MRI methodology to examine neural networks disrupted by putative axonal injury. The findings suggest that TBI is associated with altered structural and functional connectivity, characterized by decreased integrity of white matter pathways and imbalance and inefficiency of functional networks. These structural and functional alterations are often associated with neurocognitive dysfunction and poor functional outcomes. TBI has a negative impact on distributed brain networks that lead to behavioral disturbance.
    Journal of the International Neuropsychological Society 11/2015; in press. · 2.96 Impact Factor
    • "As network functionality is critically dependent on the white matter connections between cortical brain regions, analysis of its microstructure is likely to enhance our understanding of the neurodevelopmental origins of psychopathy. Diffusion tensor imaging (DTI) is a noninvasive technique that is increasingly used to examine subtle changes in the microstructural organization of white matter pathways (Jones, 2008). In DTI studies, structural connectivity is most commonly quantified as fractional anisotropy (FA), an index roughly representing the proportion of diffusion in the direction parallel to the axonal bundle (axial diffusivity, AD) relative to perpendicular diffusion (radial diffusivity, RD). "
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    ABSTRACT: Altered structural connectivity has been reported in antisocial juveniles, but findings have been inconsistent. Given the phenotypical heterogeneity among individuals showing antisocial behavior, specification of the association between structural connectivity and the dimensions of psychopathic traits (i.e., callous-unemotional, grandiose-manipulative, and impulsive-irresponsible traits) may aid in more reliably elucidating the neural mechanisms underlying antisocial behavior during adolescence. In this study, a sample of 145 adolescents (mean age 17.6, SD 1.6) from a childhood arrestee cohort participated in a neuroimaging protocol including diffusion tensor imaging (DTI). Fractional anisotropy (FA), radial diffusivity (RD) and axial diffusivity (AD), as obtained by tract-based spatial statistics, were associated with juveniles' scores on the Youth Psychopathic Traits Inventory. Grandiose-manipulative traits were positively associated with FA and negatively with RD in a wide range of white matter tracts, suggesting abnormal myelination related to these traits. Callous-unemotional traits were positively associated with FA and AD in specific white matter tracts, including the corpus callosum and corticospinal tract. The differential associations between dimensions of psychopathic traits and measures of structural connectivity support the notion that multiple distinct neural mechanisms underlie antisocial and psychopathic development. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
    Psychiatry Research: Neuroimaging 07/2015; In press(3). DOI:10.1016/j.pscychresns.2015.07.023 · 2.42 Impact Factor
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