A taxonomy of the brain’s white matter: Twenty-one major tracts for the twenty-first century

The functional and computational properties of brain areas are determined, in large part, by their connectivity profiles. Advances in neuroimaging and network neuroscience allow us to characterize the human brain noninvasively and in vivo, but a comprehensive understanding of the human brain demands an account of the anatomy of brain connections. Long-range anatomical connections are instantiated by white matter and organized into tracts. Here, we aim to characterize the connections, morphology, traversal, and functions of the major white matter tracts in the brain. It is clear that there are significant discrepancies across different accounts of white matter tract anatomy, hindering our attempts to accurately map the connectivity of the human brain. We thoroughly synthesize accounts from multiple methods, but especially nonhuman primate tract-tracing and human diffusion tractography. Ultimately, we suggest that our synthesis provides an essential reference for neuroscientists and clinicians interested in brain connectivity and anatomy, allowing for the study of the association of white matter’s macro and microstructural properties with behavior, development, and disordered processes.

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What Has Direct Cortical and Subcortical Electrostimulation Taught Us about Neurolinguistics?

The Oxford Handbook of Neurolinguistics ◽

10.1093/oxfordhb/9780190672027.013.8 ◽

2019 ◽

pp. 185-211

Author(s):

Hugues Duffau

Keyword(s):

White Matter ◽

Large Scale ◽

Functional Neuroimaging ◽

Great Accuracy ◽

Subcortical White Matter ◽

Cerebral Lesions ◽

Physiological Basis ◽

Postoperative Mri ◽

The Brain

Investigating the neural and physiological basis of language is one of the most important challenges in neurosciences. Direct electrical stimulation (DES), usually performed in awake patients during surgery for cerebral lesions, is a reliable tool for detecting both cortical and subcortical (white matter and deep grey nuclei) regions crucial for cognitive functions, especially language. DES transiently interacts locally with a small cortical or axonal site, but also nonlocally, as the focal perturbation will disrupt the entire subnetwork sustaining a given function. Thus, in contrast to functional neuroimaging, DES represents a unique opportunity to identify with great accuracy and reproducibility, in vivo in humans, the structures that are actually indispensable to the function, by inducing a transient virtual lesion based on the inhibition of a subcircuit lasting a few seconds. Currently, this is the sole technique that is able to directly investigate the functional role of white matter tracts in humans. Thus, combining transient disturbances elicited by DES with the anatomical data provided by pre- and postoperative MRI enables to achieve reliable anatomo-functional correlations, supporting a network organization of the brain, and leading to the reappraisal of models of language representation. Finally, combining serial peri-operative functional neuroimaging and online intraoperative DES allows the study of mechanisms underlying neuroplasticity. This chapter critically reviews the basic principles of DES, its advantages and limitations, and what DES can reveal about the neural foundations of language, that is, the large-scale distribution of language areas in the brain, their connectivity, and their ability to reorganize.

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Tractography Alterations in the Arcuate and Uncinate Fasciculi in Post-Stroke Aphasia

Brain Sciences ◽

10.3390/brainsci11010053 ◽

2021 ◽

Vol 11 (1) ◽

pp. 53

Author(s):

Sara Kierońska ◽

Milena Świtońska ◽

Grzegorz Meder ◽

Magdalena Piotrowska ◽

Paweł Sokal

Keyword(s):

White Matter ◽

Brain Connectivity ◽

Three Dimensional ◽

Cerebral White Matter ◽

Neural Pathways ◽

Uncinate Fasciculus ◽

Arcuate Fasciculus ◽

Fiber Tractography ◽

Post Stroke

Fiber tractography based on diffuse tensor imaging (DTI) can reveal three-dimensional white matter connectivity of the human brain. Tractography is a non-invasive method of visualizing cerebral white matter structures in vivo, including neural pathways surrounding the ischemic area. DTI may be useful for elucidating alterations in brain connectivity resulting from neuroplasticity after stroke. We present a case of a male patient who developed significant mixed aphasia following ischemic stroke. The patient had been treated by mechanical thrombectomy followed by an early rehabilitation, in conjunction with transcranial direct current stimulation (tDCS). DTI was used to examine the arcuate fasciculus and uncinate fasciculus upon admission and again at three months post-stroke. Results showed an improvement in the patient’s symptoms of aphasia, which was associated with changes in the volume and numbers of tracts in the uncinate fasciculus and the arcuate fasciculus.

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Evolutionary modifications in human brain connectivity associated with schizophrenia

Brain ◽

10.1093/brain/awz330 ◽

2019 ◽

Vol 142 (12) ◽

pp. 3991-4002 ◽

Cited By ~ 13

Author(s):

Martijn P van den Heuvel ◽

Lianne H Scholtens ◽

Siemon C de Lange ◽

Rory Pijnenburg ◽

Wiepke Cahn ◽

...

Keyword(s):

Human Brain ◽

Brain Connectivity ◽

Brain Evolution ◽

Higher Order ◽

Brain Functions ◽

Human Brain Evolution ◽

The Brain

See Vértes and Seidlitz (doi:10.1093/brain/awz353) for a scientific commentary on this article. Is schizophrenia a by-product of human brain evolution? By comparing the human and chimpanzee connectomes, van den Heuvel et al. demonstrate that connections unique to the human brain show greater involvement in schizophrenia pathology. Modifications in service of higher-order brain functions may have rendered the brain more vulnerable to dysfunction.

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Neuronal spreading and plaque induction of intracellular Aβ and its disruption of Aβ homeostasis

Acta Neuropathologica ◽

10.1007/s00401-021-02345-9 ◽

2021 ◽

Author(s):

Tomas T. Roos ◽

Megg G. Garcia ◽

Isak Martinsson ◽

Rana Mabrouk ◽

Bodil Israelsson ◽

...

Keyword(s):

Brain Homogenate ◽

Fold Increase ◽

Amyloid Beta Peptide ◽

Intracellular Accumulation ◽

Brain Areas ◽

Cellular Models ◽

Beta Peptide ◽

The Brain

AbstractThe amyloid-beta peptide (Aβ) is thought to have prion-like properties promoting its spread throughout the brain in Alzheimer’s disease (AD). However, the cellular mechanism(s) of this spread remains unclear. Here, we show an important role of intracellular Aβ in its prion-like spread. We demonstrate that an intracellular source of Aβ can induce amyloid plaques in vivo via hippocampal injection. We show that hippocampal injection of mouse AD brain homogenate not only induces plaques, but also damages interneurons and affects intracellular Aβ levels in synaptically connected brain areas, paralleling cellular changes seen in AD. Furthermore, in a primary neuron AD model, exposure of picomolar amounts of brain-derived Aβ leads to an apparent redistribution of Aβ from soma to processes and dystrophic neurites. We also observe that such neuritic dystrophies associate with plaque formation in AD-transgenic mice. Finally, using cellular models, we propose a mechanism for how intracellular accumulation of Aβ disturbs homeostatic control of Aβ levels and can contribute to the up to 10,000-fold increase of Aβ in the AD brain. Our data indicate an essential role for intracellular prion-like Aβ and its synaptic spread in the pathogenesis of AD.

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A Three-Component-System Hypothesis of Psychosis

The British Journal of Psychiatry ◽

10.1192/s0007125000295962 ◽

1989 ◽

Vol 155 (S5) ◽

pp. 37-39 ◽

Cited By ~ 42

Author(s):

Hinderk M. Emrich

Keyword(s):

Human Brain ◽

Causative Factor ◽

Microscopic Level ◽

Point Of View ◽

Component System ◽

Pathogenetic Factor ◽

Pet Scans ◽

The Brain ◽

Different Levels

Hypotheses as to the pathogenesis of schizophrenia can be discussed at different levels of a possible manifestation of the causative factor: the macroscopic-morphological, the microscopic-morphological, and the molecular. Some abnormalities have been observed on all of them: e.g. increased ventricular-brain ratios in CT, hypofrontality in SPECT and in glucographic PET-scans, and other macromorphological abnormalities (for reviews cf. Bogerts 1984; Mundt, 1986; Bogerts et al, 1987), gliosis on a microscopic level (Stevens, 1982), and an increased dopamine-binding in in vivo receptor studies (PET as well as in post-mortem studies; Cazzullo, 1988). However, the diversity and variability of these findings point to the view that rather than there being a single distinct pathogenetic factor responsible for the pathogenesis of schizophrenic psychoses, a constitutional disposition exists, which can be described as a functional dysequilibrium within the human brain. From this point of view, schizophrenia would not appear as an inherited disorder of metabolism, but as a weakness of a neurobiological ‘system’, i.e. as an interactional disorder of a complex of networks, in which the interaction between different substructures is labile in such a way that under special conditions (e.g. ‘stress’), a decompensation (functional breakdown) results. In this sense, ‘vulnerability’ to schizophrenia may be interpreted as a consequence of a constitutional deficiency of the brain which results in an inability to stabilise, under specially challenging conditions, the interaction between different substructures of the human brain. Before this ‘functional dysequilibrium-hypothesis’ (which is a special form of a constitutional structural deficiency-hypothesis) is discussed, and before the question is raised as to which are the relevant dysequilibrated components, some indication will be given as to why such an hypothesis appears plausible.

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6. What do more intelligent brains look like?

Intelligence: A Very Short Introduction ◽

10.1093/actrade/9780198796206.003.0006 ◽

2020 ◽

pp. 83-90

Author(s):

Ian J. Deary

Keyword(s):

White Matter ◽

General Intelligence ◽

Total Brain Volume ◽

Brain White Matter ◽

Total Brain ◽

Lothian Birth Cohort ◽

Intelligence Test Scores ◽

Intelligence Scores ◽

The Brain ◽

Brain Connections

‘What do more intelligent brains look like?’ considers a study that used data from the Lothian Birth Cohort 1936 to test the strength of the correlation between the general intelligence scores of the participants and different measures of their brain’s structure. Magnetic resonance imaging was used to measure total brain volume, brain cortical thickness, brain white matter integrity (or health), and brain white matter hyperintensities. The study showed that people who have higher general intelligence tend to have larger brains, thicker grey matter on the surface of the brain, and healthier white matter brain connections. The associations are not strong, but some aspects of brain structure do relate to intelligence test scores.

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Microstructural Hyperelastic Characterization of Brain White Matter in Tension

Volume 3: Biomedical and Biotechnology Engineering ◽

10.1115/imece2019-11549 ◽

2019 ◽

Author(s):

Mohammadreza Ramzanpour ◽

Mohammad Hosseini-Farid ◽

Mariusz Ziejewski ◽

Ghodrat Karami

Keyword(s):

Finite Element ◽

White Matter ◽

Human Brain ◽

Volume Fraction ◽

Fibrous Composite ◽

Diffuse Axonal Injury ◽

Stiffness Ratio ◽

Fibrous Composite Material ◽

Brain White Matter ◽

The Brain

Abstract Axons as microstructural constituent elements of brain white matter are highly oriented in extracellular matrix (ECM) in one direction. Therefore, it is possible to model the human brain white matter as a unidirectional fibrous composite material. A micromechanical finite element model of the brain white matter is developed to indirectly measure the brain white matter constituents’ properties including axon and ECM under tensile loading. Experimental tension test on corona radiata conducted by Budday et al. 2017 [1] is used in this study and one-term Ogden hyperelastic constitutive model is applied to characterize its behavior. By the application of genetic algorithm (GA) as a black box optimization method, the Ogden hyperelastic parameters of axon and ECM minimizing the error between numerical finite element simulation and experimental results are measured. Inverse analysis is conducted on the resultant optimized parameters shows high correlation of coefficient (>99%) between the numerical and experimental data which verifies the accuracy of the optimization procedure. The volume fraction of axons in porcine brain white matter is taken to be 52.7% and the stiffness ratio of axon to ECM is perceived to be 3.0. As these values are not accurately known for human brain white matter, we study the material properties of axon and ECM for different stiffness ratio and axon volume fraction values. The results of this study helps to better understand the micromechanical structure of the brain and micro-level injuries such as diffuse axonal injury.

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Delayed differential alterations in human brain volume in affected and remote brain areas after cerebral infarction measured intraindividually in vivo by 3D-MRI volumetry

NeuroImage ◽

10.1016/s1053-8119(01)92146-9 ◽

2001 ◽

Vol 13 (6) ◽

pp. 804 ◽

Cited By ~ 2

Author(s):

Matthias Kraemer ◽

Thorsten Schormann ◽

Peter Bi ◽

Georg Hagemann ◽

Karl Zilles ◽

...

Keyword(s):

Cerebral Infarction ◽

Human Brain ◽

Brain Volume ◽

3D Mri ◽

Brain Areas ◽

Mri Volumetry

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Brain connectivity in body dysmorphic disorder compared with controls: a diffusion tensor imaging study

Psychological Medicine ◽

10.1017/s0033291713000421 ◽

2013 ◽

Vol 43 (12) ◽

pp. 2513-2521 ◽

Cited By ~ 23

Author(s):

B. G. Buchanan ◽

S. L. Rossell ◽

J. J. Maller ◽

W. L. Toh ◽

S. Brennan ◽

...

Keyword(s):

Diffusion Tensor Imaging ◽

White Matter ◽

Body Dysmorphic Disorder ◽

Diffusion Tensor ◽

Brain Connectivity ◽

Imaging Study ◽

Healthy Controls ◽

Caudate Nuclei ◽

White Matter Connectivity ◽

The Brain

BackgroundSeveral neuroimaging studies have investigated brain grey matter in people with body dysmorphic disorder (BDD), showing possible abnormalities in the limbic system, orbitofrontal cortex, caudate nuclei and temporal lobes. This study takes these findings forward by investigating white matter properties in BDD compared with controls using diffusion tensor imaging. It was hypothesized that the BDD sample would have widespread significantly reduced white matter connectivity as characterized by fractional anisotropy (FA).MethodA total of 20 participants with BDD and 20 healthy controls matched on age, gender and handedness underwent diffusion tensor imaging. FA, a measure of water diffusion within a voxel, was compared between groups on a voxel-by-voxel basis across the brain using tract-based spatial statistics within the FSL package.ResultsResults showed that, compared with healthy controls, BDD patients demonstrated significantly lower FA (p < 0.05) in most major white matter tracts throughout the brain, including in the superior longitudinal fasciculus, inferior fronto-occipital fasciculus and corpus callosum. Lower FA levels could be accounted for by increased radial diffusivity as characterized by eigenvalues 2 and 3. No area of higher FA was found in BDD.ConclusionsThis study provided the first evidence of compromised white matter integrity within BDD patients. This suggests that there are inefficient connections between different brain areas, which may explain the cognitive and emotion regulation deficits within BDD patients.

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