Insular cortex

The insular cortex (abbrev. insula) lies deep to the lateral surface of the brain, completely hidden from view by the frontal, parietal and temporal opercula. It accounts for approximately 2% of cortical surface.

The insular cortex has variably been considered to be a separate lobe of the telencephalon (the "fifth lobe") or a part of other structural or functional groupings, depending on who you read. Most would refer to the insular cortex as its own area (i.e. not belonging to any of the neighbouring lobes), but not as a lobe.

The insular cortex lies hidden deep to the lateral sulcus (sylvian fissure), which separates the frontal and parietal lobes dorsally, from the temporal lobe ventrally. The overlying cortical areas formed by the frontal, parietal and temporal lobes are known as opercula (meaning "lids").

The frontoparietal operculum is formed by (from front to back):

The temporal operculum is formed by (from front to back):

The insula is a sessile irregular pyramid, with its trapezoid base facing medially. The base is circumscribed by the circular sulcus, although more precisely this is formed by four periinsular sulci; anterior, inferior, superior and posterior 3-4. Its apex points laterally, into the sylvian fissure. The insular cortex is divided into two lobules, anterior and posterior, by the central sulcus of the insula which passes obliquely from posterosuperiorly to anteroinferiorly.

The anterior lobule has a "pole" which denotes the anteroinferior most point. It's surface is divided obliquely, roughly parallel to the central sulcus of the insula, but converging inferiorly, usually by three short gyri 2. As such the anterior lobule somewhat resembles the letter "W".

The posterior lobule, is divided obliquely, parallel to the central sulcus of the insula, by two long gyri which converge anteroinferiorly at what is sometimes referred to as the "pole" of the posterior lobule 2. As such the posterior lobule somewhat resembles the letter "Y" or "V".

The insula is supplied by perforating branches from the MCA, usually from the M2 segment 5

The insula has a number of disparate functions, serving as the primary gustatory cortex, as well as having important connections to language and visual-vestibular integration 2. Additionally the insula also has important autonomic function, particularly sympathetic tone from the right insula; damage to this area has been associated with cardiac arrhythmias 2.

It is also known by the name Island of Reil, named after Johann Christian Reil.

CT

Due to tenuous collateral supply, the insula is prone to early cytotoxic oedema in acute embolic stroke involving the MCA leading to the "Loss of the insular ribbon sign" 6.

 

Neuroanatomy
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Article information

rID: 5829
Section: Anatomy
Tag: refs
Synonyms or Alternate Spellings:
  • Insula cortex
  • Insular
  • Insula

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Cases and figures

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    Figure 1
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    Figure 3: gyri
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    Figure 4: central sulcus
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    Figure 2
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