Elsevier

Neuroscience

Volume 236, 16 April 2013, Pages 117-135
Neuroscience

The human insula: Architectonic organization and postmortem MRI registration

https://doi.org/10.1016/j.neuroscience.2012.12.076Get rights and content
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Abstract

The human insula has been the focus of great attention in the last decade due to substantial progress in neuroimaging methodology and applications. Anatomical support for functional localization and interpretations, however, is still fragmented. The aim of the present study was to re-examine the microanatomical organization of the insula and relate cytoarchitectonic maps to major sulcal/gyral patterns by registration to high-resolution MR images of the same brains. The insula was divided into seven architectonic subdivisions (G, Ig, Id1–3, Ia1–2) that were charted on unfolded maps of the insula following a method used previously in monkeys. The results reveal overall similar patterns of Nissl, and to some extent also, myelin and parvalbumin (PV), as in monkeys, with a postero-dorsal to antero-ventral gradient of hypergranular to granular, dysgranular and agranular fields. Reversals occur ventrally along the inferior peri-insular sulcus (IPS), at the margin with the temporal operculum, and anteriorly at the limit with orbitofrontal cortex (OFC). A large portion of agranular cortex is characterized by a dense accumulation of the spindle-shaped von Economo neurons (VENs) in layer V. The distribution of VENs is not restricted to agranular insula but also extends into the anterior part of dysgranular fields. The patterns of intracortical myelin and of PV neuropil in the middle layers follow decreasing gradients from postero-dorsal granular to antero-ventral agranular insula, with particularly strong staining in posterior and dorsal insula. A separate PV enhanced area in the middle-dorsal insula corresponds in location to the presumed human gustatory area. Projections of the cytoarchitectonic maps onto high-resolution stereotactic MRI reveal a near concentric organization around the limen insula, with each cytoarchitectonic subdivision encompassing several major insular gyri/sulci. The dysgranular domain is the largest, taking up about half of the insula. The present study of the human insula provides a new anatomical basis for MR imaging and clinical applications.

Highlights

► Cytoarchitectonic maps of the human insula represented on unfolded maps and postmortem MRI. ► Seven subdivisions arranged from postero-dorsal (granular) to antero-ventral (agranular). ► Each subdivision expands over several insular gyri, the largest (dysgranular) over all. ► Gradient reversals point to boundaries of the insula with temporal and orbitofrontal cortices. ► The VENs area extends from the anterior agranular to anterior part of dysgranular insula.

Abbreviations

Ac
anterior commissure
ag
accessory insular gyrus
alg
anterior long insular gyrus
APS
anterior peri-insular sulcus
asg
anterior short insular gyrus
BB
band of Baillarger
CIS
central insular sulcus
FI
frontoinsular
G
hypergranular field
HG
Heschl’s gyrus
Ia
agranular insula
Id
dysgranular insula
Ig
granular insula
IPS
inferior peri-insular sulcus
Li
limen insula
msg
middle short insular gyrus
OFC
orbitofrontal cortex
pc
posterior commissure
PCIS
precentral insular sulcus
PIS
postcentral insular sulcus
plg
posterior long insular gyrus
Poc
piriform olfactory cortex
psg
posterior short insular gyrus
PuT
putamen
PV
parvalbumin
RI
retroinsular cortex
SIS
short insular sulcus
SPS
superior peri-insular sulcus
STP
superior temporal plane
tg
transverse insular gyrus
VENs
Von Economo neurons

Key words

Island of Reil
cytoarchitecture
myelin
parvalbumin
MRI projections
Von Economo neurons

Cited by (0)

Current address: Kantonsspital St. Gallen, Klinik für Neurochirurgie, Rorschacherstrasse 95, CH-9007 St. Gallen, Switzerland.

††

Current address: Spital Rorschach, Kantonsspital St.Gallen, Klinik für Chirurgie, Heidenerstrasse 11, CH-9400 Rorschach, Switzerland.