White Matter Pathway Asymmetry Underlies Functional Lateralization

AbstractHemispheric asymmetries are a central principle of nervous system architecture and shape the functional organization of most cognitive systems. Structural gray matter asymmetries and callosal interactions have been identified as contributing neural factors but always fell short to constitute a full explanans. Meanwhile, recent advances in in vivo white matter tractography have unrevealed the asymmetrical organization of many intrahemispheric white matter pathways, which might serve as the missing link to explain the substrate of functional lateralization. By taking into account callosal interactions, gray matter asymmetries and asymmetrical interhemispheric pathways, we opt for a new triadic model that has the potential to explain many observations which cannot be elucidated within the current frameworks of lateralized cognition.

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Callosal fiber length scales with brain size according to functional lateralization, evolution, and development

10.1101/2021.04.01.437788 ◽

2021 ◽

Author(s):

Liyuan Yang ◽

Chenxi Zhao ◽

Yirong Xiong ◽

Suyu Zhong ◽

Di Wu ◽

...

Keyword(s):

White Matter ◽

Fiber Length ◽

Brain Size ◽

Precentral Gyrus ◽

Neurite Density ◽

Evolution And Development ◽

Functional Lateralization ◽

Cortical Regions ◽

Parietal Cortices ◽

Length Scaling

Brain size significantly impacts the organization of white matter fibers. Fiber length scaling – the degree to which fiber length varies according to brain size – was overlooked. We investigated how fiber lengths within the corpus callosum, the most prominent white matter tract, vary according to brain size. The results showed substantial variation in length scaling among callosal fibers, replicated in two large healthy cohorts (~2000 individuals). The underscaled callosal fibers mainly connected the precentral gyrus and parietal cortices, whereas the overscaled callosal fibers mainly connected the prefrontal cortices. The variation in such length scaling was biologically meaningful: larger scaling corresponded to larger neurite density index but smaller fractional anisotropy values; cortical regions connected by the callosal fibers with larger scaling were more lateralized functionally as well as phylogenetically and ontogenetically more recent than their counterparts. These findings highlight an interaction between interhemispheric communication and organizational and adaptive principles underlying brain development and evolution.

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Review for "The distribution, number and certain neurochemical identities of infracortical white matter neurons in the brains of three megachiropteran bat species"

10.1002/cne.24894/v1/review2 ◽

2020 ◽

Keyword(s):

White Matter

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FT-IR microspectroscopic analysis of diseased white matter brain tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100141214 ◽

1995 ◽

Vol 53 ◽

pp. 968-969

Author(s):

Steven M. Le Vine ◽

David L. Wetzel

Keyword(s):

White Matter ◽

Gray Matter ◽

Twitcher Mouse ◽

Grid Pattern ◽

Marked Contrast ◽

Spatially Resolved ◽

Ft Ir ◽

Ir Microspectroscopy ◽

Chemical Evidence

In situ FT-IR microspectroscopy has allowed spatially resolved interrogation of different parts of brain tissue. In previous work the spectrrscopic features of normal barin tissue were characterized. The white matter, gray matter and basal ganglia were mapped from appropriate peak area measurements from spectra obtained in a grid pattern. Bands prevalent in white matter were mostly associated with the lipid. These included 2927 and 1469 cm-1 due to CH2 as well as carbonyl at 1740 cm-1. Also 1235 and 1085 cm-1 due to phospholipid and galactocerebroside, respectively (Figs 1and2). Localized chemical changes in the white matter as a result of white matter diseases have been studied. This involved the documentation of localized chemical evidence of demyelination in shiverer mice in which the spectra of white matter lacked the marked contrast between it and gray matter exhibited in the white matter of normal mice (Fig. 3).The twitcher mouse, a model of Krabbe’s desease, was also studied. The purpose in this case was to look for a localized build-up of psychosine in the white matter caused by deficiencies in the enzyme responsible for its breakdown under normal conditions.

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