Editing Insular cortex (section)

==Structure==
The insula is divided into an anterior and a posterior part by the '''central sulcus of the insula'''.<ref name="Kortz">{{cite web |last1=Kortz |first1=Michael W. |last2=Lillehei |first2=Kevin O. |title=Insular Cortex |url=https://www.ncbi.nlm.nih.gov/books/NBK570606/ |website=StatPearls |publisher=StatPearls Publishing |date=2024}}</ref>

===Connections===
The anterior part of the insula is subdivided by shallow [[Sulcus (neuroanatomy)|sulci]] into three or four '''short gyri'''.

The anterior insula receives a direct projection from the basal part of the [[Ventral nuclear group|ventral medial nucleus]] of the thalamus and a particularly large input from the [[central nucleus of the amygdala]]. In addition, the anterior insula itself projects to the [[amygdala]].

One study on rhesus monkeys revealed widespread reciprocal connections between the insular cortex and almost all subnuclei of the amygdaloid complex. The posterior insula projects predominantly to the dorsal aspect of the lateral and to the central amygdaloid nuclei. In contrast, the anterior insula projects to the anterior amygdaloid area as well as the medial, the cortical, the accessory basal magnocellular, the medial basal, and the lateral amygdaloid nuclei.<ref>{{cite journal|last=MUFSON|first=E|author2=MESULAM, M |author3=PANDYA, D |title=Insular interconnections with the amygdala in the rhesus monkey|journal=Neuroscience|date=1 July 1981|volume=6|issue=7|pages=1231–1248|doi=10.1016/0306-4522(81)90184-6|pmid=6167896|s2cid=46366616}}</ref>

The posterior part of the insula is formed by a '''long gyrus'''.

The posterior insula connects reciprocally with the [[secondary somatosensory cortex]] and receives input from [[spinothalamic tract|spinothalamically]] activated [[Ventral nuclear group|ventral posterior inferior]] thalamic nuclei. It has also been shown that this region receives inputs from the ventromedial nucleus (posterior part) of the thalamus that are highly specialized to convey homeostatic information such as pain, temperature, itch, local oxygen status, and sensual touch.<ref>{{cite journal |vauthors=Craig AD, Chen K, Bandy D, Reiman EM | year = 2000 | title = Thermosensory activation of insular cortex | journal = Nat. Neurosci. | volume = 3 | issue = 2| pages = 184–90 | doi = 10.1038/72131 | pmid = 10649575 | s2cid = 7077496 }}</ref>

A human neuroimaging study using [[diffusion MRI|diffusion tensor imaging]] revealed that the anterior insula is interconnected to regions in the temporal and occipital lobe, opercular and orbitofrontal cortex, triangular and opercular parts of the inferior frontal gyrus. The same study revealed differences in the anatomical connection patterns between the left and right hemisphere.<ref>{{cite journal|last=JAKAB|first=A|author2=MOLNAR, P |author3=BOGNER, P |author4=BERES, M |author5=BERENYI, E |title= Connectivity-based parcellation reveals interhemispheric differences in the insula|journal=Brain Topography|date=1 Oct 2011| doi= 10.1007/s10548-011-0205-y|pmid=22002490|volume=25 |issue=3 |pages=264–271|s2cid=12293575}}</ref>

The '''circular sulcus of insula''' (or '''sulcus of Reil'''<ref name="Sobotta's Atlas and Text-book of human anatomy 1909">{{cite web | url=http://babel.hathitrust.org/cgi/pt?q1=circular%20sulcus;id=ien.35558004773517;view=plaintext;seq=243;start=1;size=100;page=root;num=145;orient=0 | title=Sobotta's Atlas and Text-book of human anatomy 1909 | access-date=November 10, 2013 | author= Johannes Sobotta | pages=145}}</ref>) is a semicircular [[sulcus (neuroanatomy)|sulcus]] or ''fissure''<ref name="Sobotta's Atlas and Text-book of human anatomy 1909" /> that separates the insula from the neighboring gyri of the [[operculum (brain)|operculum]]<ref>{{cite web| publisher=MediLexicon| title=Definition: 'Circular Sulcus Of Insula'| access-date=2012-03-30| url=http://www.medilexicon.com/medicaldictionary.php?t=86332| archive-date=2013-06-04| archive-url=https://web.archive.org/web/20130604181646/http://www.medilexicon.com/medicaldictionary.php?t=86332| url-status=dead}}</ref> in the front, above, and
behind.<ref name="Sobotta's Atlas and Text-book of human anatomy 1909" />

===Cytoarchitecture===
The insular cortex has regions of variable cell structure or [[cytoarchitecture]], changing from [[granule cell|granular]] in the [[Posterior (anatomy)|posterior]] portion to agranular in the [[anterior]] portion. The insula also receives differential [[cerebral cortex|cortical]] and [[thalamus|thalamic]] input along its length.  The anterior insular cortex contains a population of [[spindle neurons]] (also called ''von Economo neurons''), identified as characterising a distinctive subregion as the agranular frontal insula.<ref>{{cite journal|last1=Bauernfeind A|title =A volumetric comparison of the insular cortex and its subregions in primates|journal=Human Evolution|date=April 2013|volume=64 | issue = 4 |pages=263–279|doi=10.1016/j.jhevol.2012.12.003|pmc=3756831|display-authors=etal|pmid=23466178|bibcode =2013JHumE..64..263B}}</ref>

===Development===
The insular cortex is considered a separate [[lobes of the brain|lobe]] of the [[telencephalon]] by some authorities.<ref>[http://encarta.msn.com/encyclopedia_761555359/Brain.html Brain], MSN Encarta. [https://web.archive.org/web/20091028015600/http://encarta.msn.com/encyclopedia_761555359/Brain.html Archived] 2009-10-31.</ref> Other sources see the insula as a part of the [[temporal lobe]].<ref>{{cite book |author1=Kolb, Bryan |author2=Whishaw, Ian Q. |title=Fundamentals of human neuropsychology |publisher=Worth |location=[New York] |year=2003 |isbn=978-0-7167-5300-1 |edition=5th}}</ref> It is also sometimes grouped with limbic structures deep in the brain into a [[limbic lobe]].{{Citation needed|date=March 2008}} As a paralimbic cortex, the insular cortex is considered to be a relatively old structure.