2. Insula
The Hidden Cortex
The insula is the cortical part of the brain
that is not visible when looking at the
surface of the brain.
Rebecca E. Martin
January, 2009
7. The Insula Looks Like a
Seashell FIG 2. The transverse gyrus and the orbitofrontal insula rela-
tionship. Base view of the orbital surface of the left frontal lobe
after resection of part of the gyrus rectus (GR) and the anterior
portion of the temporal lobe (T). Medial is to the reader’s left. I
indicates olfactory bulb; II, optic chiasm and tract. The H-shaped
orbital sulcus (arrowheads) defines the MOG, POG, anterior
orbital gyrus (AOG), and lateral orbital gyrus (LOG). At the pos-
teromedial aspect of the orbitofrontal surface, the posterior por-
tion of the MOG merges with the medial portion of the POG to
form the prominent PMOL. PMOL gives rise to the transverse
insular gyrus (t) that extends laterally to form the pole (po) of the
insula just anteroinferomedial to the apex (asterisk) of the insula.
The CS (dashed line) curves inferiorly immediately behind and
below the apex and the pole en route to join the stem of the
sylvian fissure. The ASG (a) and the PSG (p) converge to form the
apex of the insula anterior to the CS. In this image, the deliberate
slight rotation used to illustrate the course of the transverse
gyrus from the PMOL to the pole also rotates the apex medially,
so the apex does not appear to lie as far lateral in position as it
would in a true base view.
cases, including two in which the MSG was equal to
the ASG in size).
FIG 1. A–C, Anatomy of the convexity surface of the left insular
The PSG formed the precentral gyrus of the insula
lobe after resection of the overlying opercula, vessels, and pia-
immediately anterior to the CS in all cases. Typically,
arachnoid. Gross anatomic specimens from a 50-year-old woman
(A), a 63-year-old man (B), and a 71-year-old man (C). The anterior the short insular sulcus separated the ASG from the
PS (APS), superior PS (SPS), and inferior PS (IPS) define the base
MSG, whereas the precentral sulcus of the insula
of the insular lobe. The oblique CS of the insula subdivides the
separated the MSG from the PSG (Table 2). In one
insula into larger anterior and smaller posterior lobules.
case with absent MSG, the short insular sulcus and
Anterior lobule: The ASG (a), MSG (m), and PSG (p) form most
of the convexity surface of the anterior lobule. The short insular the precentral sulcus merged completely, so they
sulcus (SIS) separates ASG from MSG. The precentral sulcus
could not be identified as separate structures.
(preCS) separates MSG from PSG. MSG shows variable size and
The apex of the insula was formed by the short gyri
depression below the surface of the insula. The number of gyri
Naidich et al., 2004
in all cases, but the specific pattern of the short gyri
on the convexity surface of the anterior lobule varies substan-
tially: two in A, three in B, and four in C. The apex (asterisk) of the and the contribution of each short gyrus to the apex
insula forms by the convergence of the inferior ends of some or
were variable (Fig 1). The ASG contributed to the
43. granular
dysgranular
agranular
granular - 6 layers
dysgranular - 5-ish layers
agranular - 5 or less layers
Augustine, 1996
44. granular
dysgranular
agranular
Wow, that’s similar
to the OFC and the
granular - 6 layers Cingulate!
dysgranular - 5-ish layers
agranular - 5 or less layers
Augustine, 1996
58. A Primary Gustatory Area
Taste (lesion studies
indicate taste intensity
and recognition problems)
59. A Primary Gustatory Area
Taste (lesion studies
indicate taste intensity
and recognition problems)
Fun fact: Taste info from
both sides of mouth
passes though left insula
60. Activation Studies
The Insula is:
A Visceral Sensory Area
Role in integration of
multimodal sensory
information, gut feelings,
disgust, temperature
perception, pain recognition
Interoception i.e. “How We
Feel”
63. The (left) Insula is also:
Involved in Language and Memory
Part of an “articulatory loop”
Coordinates speech articulation
Singing!
(Right insula may mediate control of vocal tract)
Insula lesions have been noted to cause aphasia
Part of network involved in verbal memory - mental navigation
along memorized routes (hippocampus -> precuneus -> insula)
Humor (particularly gag and language humor, Watson et al., 2006)
64. Lesion Studies
The Insula:
Is associated with certain types of
mental illness
Early Alzheimers (atrophy)
Schizophrenia (abnormalities, e.g. decreased
grey matter)
OCD, PTSD, Anxiety, Depression
May Play a Role in Addiction
Conscious urges to take drugs (Naqvi,
Bechara, Damasio, 2008)
66. References
Afif, A., Bouvier, R., Buenerd, A., Trouillas, J., & Mertens, P. (2007). Development of the human fetal insular cortex:
study of the gyration from 13 to 28 gestational weeks. Brain Structure and Function, 212(3), 335-346.
Augustine, J. R. (1996). Circuitry and functional aspects of the insular lobe in primates
including humans. Brain Research Reviews, 22(3), 229-244.
Augustine, J. R. (1985). The insular lobe in primates including humans. Neurological Research, 7(1), 2-10.
Balleine, B. W., & Dickinson, A. (2000). The Effect of Lesions of the Insular Cortex on Instrumental Conditioning:
Evidence for a Role in Incentive Memory. J. Neurosci., 20(23).
Cereda, C., Ghika, J., Maeder, P., & Bogousslavsky, J. (2002). Strokes restricted to the insular cortex. Neurology,
59(12), 1950-1955.
Craig, A. (. (2003). Interoception: the sense of the physiological condition of the body. Current Opinion in
Neurobiology, 13(4), 500-505.
Critchley, H. D., Wiens, S., Rotshtein, P., Ohman, A., & Dolan, R. J. (2004). Neural systems supporting interoceptive
awareness. Nat Neurosci, 7(2), 189-195.
Manger, P., Sum, M., Szymanski, M., Ridgway, S., & Krubitzer, L. (1998). Modular Subdivisions of Dolphin Insular
Cortex: Does Evolutionary History Repeat Itself? Journal of Cognitive Neuroscience, 10(2), 153-166.
Morris, J. (2002). How do you feel? Trends in Cognitive Sciences, 6(8), 317-319.
Nagai, M., Kishi, K., & Kato, S. (2007). Insular cortex and neuropsychiatric disorders: A review of recent literature.
European Psychiatry, 22(6), 387-394.
Naidich, T. P., Kang, E., Fatterpekar, G. M., Delman, B. N., Gultekin, S. H., Wolfe, D., et al. (2004). The Insula:
Anatomic Study and MR Imaging Display at 1.5 T. AJNR Am J Neuroradiol, 25(2), 222-232.
Naqvi, N. H., Rudrauf, D., Damasio, H., & Bechara, A. (2007). Damage to the Insula Disrupts Addiction to Cigarette
Smoking. Science, 315(5811), 531-534.
Oppenheimer, S. (2006). Cerebrogenic cardiac arrhythmias: Clinical Autonomic Research. Clin Auton Res, 16(1),
6-11.
Türe U, Yasargil DCH, Al-Mefty O, Yasargil MG. (1999). Topographic anatomy of the insular region. J Neurosurg,
90, 720 –733
Türe U, Yasargil MG, Al-Mefty O, Yasargil DCH. (2000). Arteries of the insula. J Neurosurg, 92:676 – 687
•The insular lobe corresponds to the fifth lobe of the brain including Brodmann areas 13 through 16
- The insula is located deep inside the brain, at the base of the Sylvian Fissure. 
•it is the only cortical part of the brain that is not visible when looking at the surface of the brain
•The central insular sulcus, divides the insula into two zones that are unequal in size: the anterior insula (larger) and posterior insula (smaller).
•Anterior= 3-5 short gyri number of gyri are highly varied by person and side of the brain
Posterior = 2 long gyri
•The insula encapsulates the claustrum and putamen (i.e. the lenticular nucleus).
•posterior to the pars triangularis
•Insula adjacent to lateral ventricle except for base of insula (in the C-shaped curve of the ventricle).
•It is separated from the operculum by the anterior, superior, and inferior periinsular sulci.
•It is covered from opercula by a layer of arteries
showing a coronal section of the brain through the foramen of Monro and the amygdala, anterior view.
\"the insula connects with portions of the frontal, parietal, and temporal lobes and with the cingulate gyrus.These investigators have also shown that the basal nuclei (in particular, the tail of the caudate nucleus, the putamen,
and the claustrum), the amygdaloid body and other limbic structures, and the dorsal thalamus also connect with the insula.\"
•Insula adjacent to lateral ventricle except for base of insula (in the C-shaped curve of the ventricle).
The insula and basal gangion areas
axial section of the right cerebral hemisphere through the insula, superior view. Abbreviations with white letters denote sulci and fissures.
-ahg = anterior Heschl’s gyrus;
-bf = body of fornix;
-c = claustrum;
-cg = cingulate gyrus;
-cn = caudate nucleus;
-crf = crus of fornix;
-ec = external capsule;
-exc = extreme capsule;
-gcc = genu of corpus callosum;
-gp = globus pallidus;
-ic = internal capsule;
-p = putamen;
-scc = splenium of corpus callosum;
-sf = sylvian fissure;
-t = thalamus.
Fiber dissection of this area reveals vascularization of the lentiform nuclei (which have been removed) and vascularization of the internal capsule by the LLAs (arrow), which arise from M1 segment. (INTERNAL CAPSULE)
-ac = anterior commissure;
-cis = central insular sulcus;
- ia = insular apex;
-ic = internal capsule;
The insula encapsulates the claustrum and putamen (i.e. the lenticular nucleus).
Insula fed entirely by MCA
1. The same specimen is shown following removal of the entire opercula with preservation of all segments of the MCA.
2. The same specimen. The M 3 , M 4 and M 5 segments of the MCA have been removed, and the M 2 segment, which supplies the insula, has been preserved over the insular cortex.
3. The insula is shown following removal of the frontal, parietal, occipital, and temporal lobes from the periinsular sulci. The arteries of the insula originate from the M2segment. The insulo-opercular arteries (arrows)supply the insula and operculum.
dense wall of arteries running in the lateral fissure. The deep anatomical location of the insular cortex together with the dense sylvian vascularization explains why the insula has rarely been investigated in humans.
Drawings showing that approximately 85 to 90% of insular arteries were short and supplied the insular cortex (i) and extreme capsule; 10% were medium sized and supplied, in addition, the claustrum and external capsule; and the remainder 3 to 5%
were long and extended as far as the corona radiata (cr). a = amygdala; gp = globus pallidus; p = putamen. See previous figure legends for additional abbreviations.
•(Afif et al., 2007) Insula part of the telencephalon.
•surface expansion is more limited than that of the other 4 cortices.
•It is suggested that cortical maturation (sulcation and gyration) and vascularization of the lateral surface of the brain starts with the insular region, suggesting that this region is a central area of cortical development
•Right side develops earlier but left side usually ends up larger in adults (language function?)
•First cortex to grow.  It is anchored to underlying structures so maintains its position while the temporal lobe pivots around it.  Then becomes covered as lobes enlarge.
