orientation using a bootstrap approach. Un-
certainty was typically low, with a 95% confi-
dence interval≤3° in 90% of the white matter
pixels (fig. S5). Higher values of uncertainty
were localized mostly to the centrum semiovale.
Besides fiber crossing, we found that other
potential sources of signal typically did not
affect the peak orientation extracted with
Nissl-ST. These other sources include blood
vessels (figs. S6 and S7) as well as backgroundfibrous structures (figs. S8 and S9). Although
the blood volume in white matter is estimated
to be only 2.57% ( 32 ), the estimated peak orien-
tation could be affected in atypical regions with
very high blood vessel volume (fig. S7). Rare764 5NOVEMBER2021¥VOL 374 ISSUE 6568 science.orgSCIENCE
Fig. 2. Comparison of Nissl-based structure tensor with other methods.
(AtoC) In-plane orientation maps in coronal slices of the right hemisphere
from three different human datasets. (A) Nissl-ST (effective resolution
~15mm, visualized with 200mm–by– 200 mm tiles). (B) PLI (in-plane
resolution 1.3mmby1.3mm). [Image reproduced with permission from
Axer, Amunts, and colleagues at Forschungszentrum Jülich GmbH]. (C) In vivo
diffusion MRI (resolution of 1.25 mm isotropic), showing peak orientations
projected onto the plane. To minimize sharp transitions in the more granular
diffusion data, we smoothed the image using a median filter (see unsmoothed
image in fig. S3). All methods estimate similar orientations for the in-plane
axons, even in regions where the predominant fiber bundle crosses
perpendicular to the plane, such as the ILF (dashed ellipse; see fig. S2)
(DtoF) Magnified views of the regions indicated in (A) to (C), visualized
with 50mm–by– 50 mm tiles. (D) Local inhomogeneity in the corpus callosum.
(E) Axons of the lenticular fasciculus (red, indicated by black arrowheads)
that connect the subthalamic nucleus and the internal globus pallidus
and pass through the internal capsule (green), giving rise to the interchanging
pattern of crossing fibers known as Edinger’s comb. (F) The angular
bundle (yellow, indicated by white arrowheads), which connects the
hippocampus and entorhinal cortex.RESEARCH | REPORTS