It is now known to the vast majority of the population that the human brain is divided into four cerebral lobes.
With a simple picture of the brain, we could locate a large number of parts of the brain. However, there is a very relevant structure that can remain hidden from visual observation, given that it is found at a certain depth after one of the main furrows of the brain. This structure is called the insula.
What is the island?
Also considered to be the fifth cerebral lobe, the insula is a structure of the cerebral cortex located in the depth of the Silvio slit, at the point of convergence of the temporal, parietal and frontal lobes, bounded by their respective opercles.
The insula is part of the mesocortex, or paralimbic system, alongside the orbitofrontal and other structures. It is a connection center between the limbic system and the neocortex, participating in many different functions, directly or indirectly.
Part of the cerebral cortex
Being clear about the makeup of the cerebral cortex can help you understand the type of processes that take place on the island.
The cortex of the brain, of which the insula is a part, is the rough part that extends over most of the outside of the brain. However, as we have seen, it is not defined as being on the outside and fully exposed to observation, as the insula is hidden and the brain must be manipulated to see it. However, the reason why it is in the superficial part of the central nervous system is the same why the rest of the cortex is arranged this way: the need to accumulate gray matter in strategic areas.
Gray matter is made up of neural sums, What are the parts of neurons in which the nucleus is located and in which the most important processes of nerve transmission take place. These receive information from other parts of the nervous system and at the same time send information to others.
But centralizing all these tasks requires space, and that’s why there is the cerebral cortex: its rough, folded shape is made to be able to concentrate as much gray matter as possible in it, in an almost uninterrupted continuum along from the outside. (and not so external, depending on the depth of the folds and cracks) of the brain.
like that, the insula and the rest of the brain lobes are not passage areas for nerve impulsesBut regions in which complex psychological processes take place and in which information from very diverse areas of the nervous system is integrated.
The island is not only a uniform structure that performs the same functions in a homogeneous way, but different parts of this structure are in charge of various tasks. Specifically, the insula is divided into anterior and posterior insula, the two parts separated by the central insular groove.
The posterior region of the insula is mainly more innervated with somatosensory neurons, which are the ones that create a “map” of positional sensations related to different parts of the body. so that the participation of this region was more closely related to the control of viscera and internal organs.
The anterior part of this brain structure has a more important connection with the limbic system, its functionality being more oriented towards the emotional integration of experiences and perceptions as a unitary and whole sensation.
Main functions of the island
Let’s take a look at some of the main features of the island region.
As we have seen, the island influences a large number of basic and higher processes (related to abstract thinking and decision making), and is an element of great importance for the proper functioning and even the survival of the organism. In this sense, research conducted in the field of neuroscience reflects that the island participates in the following processes.
1. Perception of taste and smell
The sense of taste has its main primary sensory zone at the end of the island and in the parietal cortex. It is at this moment that taste information becomes conscious, appearing as a private and subjective experience but linked to the elements of the environment that we savor.
It has also been observed that the insula participates in the perception of smell, although this sense tends to have a neural network scattered throughout the brain.
2. Visceral control and somatoperception
The insula also plays an important role in the regulation of viscera and organs. More precisely, it has been observed that its experimental manipulation produces significant variations in blood pressure and heart rate. It also participates in the sensations coming from the digestive system, also participating in the management of this system and the respiratory system.
3. Vestibular function
Vestibular function, which refers to bodily balance and control of the body over space, also exhibits afferents in the island region, being a relevant core in its conscious perception. So, thanks to the island, a healthy person can know what position each of the main parts of his body occupies at any time.
4. Integration of emotional and perceptual information
The island, as mentioned above, it acts as a zone of association between very different observations, Especially with regard to the association between perception and emotion.
So, thanks in part to this region of the brain, we learn from our experiences, connecting pleasant or unpleasant subjective sensations to what we do and say and, in this way, we associate behaviors with consequences through what we perceive. .
5. Involvement in addictions: desires and envy
Due to its relationship and connections to the limbic system, the link between the insula and the brain reward system has been explored. Research has shown that this structure is involved in the processes of addiction to certain drugs, helping to maintain addictive behavior.
This relationship is due to the involvement of the island region with the integration between emotion and cognition, Be particularly involved in the phenomenon of craving or intense desire for consumption.
6. Empathy and emotional recognition
We have already seen that the island has very good links with the limbic system. In this regard, recent research has indicated that this region of the cerebral cortex plays a key role in the ability to recognize emotions and empathy. Thus, it has been shown that individuals without an insula show much less recognition, especially with regard to the emotions of joy and surprise, as well as pain.
In fact, it has been suggested that the deficits seen are very similar to some cases of autism, borderline personality disorder, and behavioral problems, so research could be done on how this area of the brain works in some. troubles.
Allen, GV; Saper, CB; Hurley, KM and Cechetto, DF (1991). Location of visceral and limbic connections in the rat island cortex. J Comp Neurol; 311: 1-16
Craig, AD; Reiman, EM; Evans, A. and Bushnell, MC (1996). Functional image of an illusion of pain. Nature; 384: 258-260
Duc, JE; Hernán, O. and Devia, A. (2004). The island lobe. A visceral cortical processing lobe. Acta Neurol. Colom. Vol 20, 2.
Guenot, M .; Isnard, J. and Sindou, M. (2004) Surgical anatomy of the insula. Adv Tech Stand Neurosurg; 29: 265-288
Guyton, AC and Hall, JE (2008): Treatise on medical physiology (11th ed.). Madrid, Elsevier.
Kandel, ER; Schwartz, JH; Jessell, TM (2001). Principles of neuroscience. Madrird: MacGrawHill
Kivity, S .; Ortega-Hernández, OD and Shoenfeld, Y. (2009). Olfaction a window to the mind. Isr Med Assoc J; 11: 238-43
Kolb, B. and Wishaw, I. (2006). Human neuropsychology. Madrid: Editorial Mèdica Panamericana
Manes, F. and Niro, M. (2014). Use your brain. Buenos Aires: Planet.
Netter, F. (1989). The nervous system. anatomy and physiology. Volume 1.1. Barcelona: registered
Ostrowsky, K .; Isnard, J .; Ryvlin, P .; Guénot, M .; Fischer, C. i Mauguière, F. (2000). Functional mapping of the insular cortex: clinical implication in temporal lobe epilepsy. Epilepsy; 41: 681-6
Pedrosa-Sánchez, M .; Escosa-Bagé, M .; García-Navarrete, I. and Sola, RG (2003). Reil Island and drug resistant epilepsy. Tower. Neurol .; 36 (1): 40-44
Snell, RS (1999). Clinical neuroanatomy. Buenos Aires: Editorial Mèdica Panamericana, SA: 267.
Türe, U .; Yasargil, DCH; Al-Mefty, O. and Yasargil, MG (1999). Topographic anatomy of the island region. J Neurosurg; 90: 720-33.
Varnavas, GG and Grand, W. (1999). The insular cortex: anatomical, morphological and vascular characteristics. Neurosurgery; 44: 127-38