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@ARTICLE{Bisten:279356,
author = {Bisten, Justus and Grün, Johannes and Hoppe, Christian and
Bauer, Tobias and Held, Nina Rebecca and Rose, Renata and
Althausen, Anita and Witt, Juri-Alexander and Borger, Valeri
and Schneider, Matthias and Vatter, Hartmut and
Helmstaedter, Christoph and Radbruch, Alexander and Surges,
Rainer and Schultz, Thomas and Rüber, Theodor},
title = {{S}tructural {W}hite {M}atter {C}orrelates of the
{C}rowding {E}ffect: {I}nsights {F}rom a {T}ractography
{S}tudy of the {A}rcuate {F}asciculus
{P}ost-{H}emispherotomy.},
journal = {Human brain mapping},
volume = {46},
number = {9},
issn = {1065-9471},
address = {New York, NY},
publisher = {Wiley-Liss},
reportid = {DZNE-2025-00733},
pages = {e70258},
year = {2025},
abstract = {The neuropsychological crowding effect denotes the
reallocation of cognitive functions within the
contralesional hemisphere following unilateral brain damage,
prioritizing language at the expense of nonverbal abilities.
This study investigates structural white matter correlates
of crowding in the arcuate fasciculus (AF), a key language
tract, using hemispherotomy as a unique setting to explore
structural reorganization supporting language preservation.
We explore two main hypotheses. First, the contralesional
right AF undergoes white matter reorganization correlated
with preserved language function at the expense of nonverbal
abilities following left-hemispheric damage. Second, this
reorganization varies with epilepsy etiology, influencing
different stages of developmental language lateralization.
This retrospective study included individuals
post-hemispherotomy and healthy controls. Inclusion criteria
were; (1) being a native German speaker, (2) having no MRI
contraindication, (3) the ability to undergo approximately 2
h of MRI scans, and (4) the ability to participate in
neuropsychological assessments over two consecutive days.
Neuroimaging included T1-, T2-, and diffusion-weighted
imaging, alongside postoperative neuropsychological
assessments, where it was taken as evidence for crowding if
verbal IQ exceeded performance IQ by at least 10 points. The
AF was reconstructed using advanced tractography, and
CoBundleMAP was used to compare morphologically
corresponding AF subsections. Statistical significance was
set at $ p<0.05 $ , with correction for multiple comparisons
applied across contiguous tract sections using
Threshold-Free Cluster Enhancement. The final cohort
comprised 22 individuals post-hemispherotomy (median age: $
20.4 $ years, range: $ 12.3-43.9 $ ; 55\% female; 55\% with
left-sided surgeries) and 20 healthy controls (median age: $
23.8 $ years, range: $ 15.5-54.0 $ ; 55\% female). Crowding
was associated with significantly higher fractional
anisotropy (FA) in the AF ( $ p=0.015 $ , Cohen's $ d=1.69 $
), but only observed in individuals with left-sided
hemispherotomy, localized to a subsection between
Geschwind's territory and Wernicke's area ( $
{p}_{\mathrm{corrected}}=0.02 $ ). This region also
displayed significantly higher normalized FA in AF of
individuals with congenital etiology and crowding compared
to acquired etiology and no crowding ($
{p}_{\mathrm{corrected}}=0.0189 $ ). This study identifies
previously unreported neural correlates of crowding in right
contralesional AF of individuals post-hemispherotomy and
highlights specific AF subsections involved in preserving
language functions at the cost of nonverbal abilities. The
findings suggest a link between crowding and epilepsy
etiology, particularly in the region spanning Geschwind's
territory and Wernicke's area.},
keywords = {Humans / Female / White Matter: diagnostic imaging / White
Matter: pathology / Male / Diffusion Tensor Imaging / Adult
/ Retrospective Studies / Hemispherectomy / Young Adult /
Functional Laterality: physiology / Middle Aged / Adolescent
/ Language / Neural Pathways: diagnostic imaging},
cin = {AG Stöcker / AG Radbruch},
ddc = {610},
cid = {I:(DE-2719)1013026 / I:(DE-2719)5000075},
pnm = {353 - Clinical and Health Care Research (POF4-353)},
pid = {G:(DE-HGF)POF4-353},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:40536189},
pmc = {pmc:PMC12177811},
doi = {10.1002/hbm.70258},
url = {https://pub.dzne.de/record/279356},
}