Insular cortex
From Wikipedia, the free encyclopedia
| Brain: Insular cortex | ||
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| The insula of the left side, exposed by removing the opercula. | ||
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| Coronal section of brain immediately in front of pons. (Insula labeled at upper right.) | ||
| Latin | lobus insularis | |
| Gray's | subject #189 825 | |
| Artery | Middle cerebral | |
| NeuroNames | hier-93 | |
| Dorlands/Elsevier | i_09/12454066 | |
The insular cortex (abbrev. insula) is a structure of the human brain. It lies deep to the brain's lateral surface, within the lateral sulcus which separates the temporal lobe and inferior parietal cortex. These overlying cortical areas are known as opercula (meaning "lids"), and parts of the frontal, temporal and parietal lobes form opercula over the insula. The Latin name for the insular cortex is lobus insularis.
The insular cortex is also known by the name Island of Reil, named after Johann Christian Reil.
The insular cortex is considered a separate lobe of the telencephalon by some authorities.[1] It is also sometimes grouped with limbic structures deep in the brain into a limbic lobe.
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[edit] Contrasting anterior and posterior architecture
It has regions of variable cell structure or cytoarchitecture, changing from granular in the posterior portion to agranular in the anterior portion. The insula also receives differential cortical and thalamic input along its length. The anterior insula receives a direct projection from the basal part of the ventral medial nucleus (VMb) of the thalamus and a particularly large input from the central nucleus of the amygdala. Additionally, the anterior insula itself projects to the amygdala. The posterior insula connects reciprocally with the secondary primary sensory cortex (S2) and receives input from spinothalamically activated ventral posterior inferior (VPI) thalamic nuclei. More recent work by Bud Craig and his colleagues has shown that this region receives inputs from the ventromedial nucleus (posterior part) of the thalamus that are highly specialized to convey emotional/homeostatic information such as pain, temperature, itch, local oxygen status and sensual touch.
[edit] Role in emotions and feelings (relationship to the "limbic system")
The insular cortex, in particular its most anterior portion, is considered a limbic-related cortex. The insula has increasingly become the focus of attention for its role in body representation and subjective emotional experience. In particular, Antonio Damasio has proposed that this region plays a role in mapping visceral states that are associated with emotional experience, giving rise to conscious feelings. This is in essence a neurobiological formulation of the ideas of William James, who first proposed that subjective emotional experience (i.e. feelings) arise from our brain's interpretation of bodily states that are elicited by emotional events. This is an example of embodied cognition.
Functionally speaking, the insula is believed to process convergent information to produce an emotionally relevant context for sensory experience. More specifically, the anterior insula is related more to olfactory, gustatory, vicero-autonomic, and limbic function, while the posterior insula is related more to auditory-somesthetic-skeletomotor function. Functional imaging experiments have revealed that the insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness and sadness.
Functional imaging studies have also implicated the insula in conscious desires, such as food craving and drug craving. What is common to all of these emotional states is that they each change the body in some way and are associated with highly salient subjective qualities. The insula is well situated for the integration of information relating to bodily states into higher-order cognitive and emotional processes. The insula receives information from "homeostatic afferent" sensory pathways via the thalamus and sends output to a number of other limbic-related structures, such as the amygdala, the ventral striatum and the orbitofrontal cortex.
A single study using magnetic resonance imaging has found that the right anterior insula was significantly thicker in people who meditate.[2]
[edit] Smoking
Recent research led by Nasir Naqvi at the University of Iowa has shown that cigarette smokers who suffer damage to the insular cortex, from a stroke for instance, have their addiction to cigarettes practically eliminated. These individuals were found to be up to 136 times more likely to undergo a disruption of smoking addiction than smokers with damage in other areas. Disruption of addiction was evidenced by self-reported behavior changes such as quitting smoking less than one day after the brain injury, quitting smoking with great ease, not smoking again after quitting, and having no urge to resume smoking since quitting. This suggests a significant role for the insular cortex in the neurological mechanisms underlying addiction to nicotine and other drugs, and would make this area of the brain a promising target for novel anti-addiction medications (or possibly transcranial magnetic stimulation.)[3]
[edit] Phylogenetic considerations
As a paralimbic cortex, the insular cortex is considered to be a relatively old structure. It plays a role in a variety of highly conserved functions that are related to basic survival needs, such as taste, visceral sensation and autonomic control (so-called homeostatic functions). There is evidence that in addition to its more conserved functions, the insula may play a role in certain "higher" functions that operate only in humans and other great apes. John Allman and his colleagues have shown that the anterior insular cortex contains a population of neurons, called spindle neurons, that are specific to great apes. These neurons are also found in the anterior cingulate cortex, which is another region that has reached a high level of specialization in great apes. Spindle neurons are found at a higher density in the right insular cortex. It has been speculated that these neurons are involved in cognitive-emotional processes that are specific to great apes, such as empathy and self-aware emotional feelings. This is supported by functional imaging results showing that the structure and function of the right anterior insula are correlated with the ability to feel one's own heartbeat, or to empathize with the pain of others. It is thought that these functions are not distinct from the "lower" functions of the insula, but rather arise as a consequence of the role of the insula in conveying homeostatic information to consciousness.
[edit] Additional images
 Coronal section through mid-brain. |
 Coronal section of brain through intermediate mass of third ventricle. |
 Coronal section through anterior cornua of lateral ventricles. |
 Coronal section of brain through anterior commissure. |
 Orbital surface of left frontal lobe. |
 Section of brain showing upper surface of temporal lobe. |
 Horizontal section of right cerebral hemisphere. |
[edit] References
- ^ Brain, MSN Encarta.
- ^ Sara W. Lazar, Catherine E. Kerr, Rachel H. Wasserman, Jeremy R. Gray, Douglas N. Greve, Michael T. Treadway, Metta McGarvey, Brian T. Quinn, Jeffery A. Dusek, Herbert Benson, Scott L. Rauch, Christopher I. Moore, and Bruce Fischl (November 2005). "Meditation experience is associated with increased cortical thickness". NeuroReport 16 (17): 1893-1897.
- ^ Nasir H. Naqvi, David Rudrauf, Hanna Damasio, Antoine Bechara. (2007). "Damage to the Insula Disrupts Addiction to Cigarette Smoking". Science 315 (5811): 531-534. DOI:10.1126/science.1135926.
[edit] See also
[edit] External links
- BrainMaps at UCDavis insular cortex
- synd/1212 at Who Named It
- A Small Part of the Brain, and Its Profound Effects, New York Times
- Roche Lexicon - illustrated navigator, at Elsevier 13048.000-1
