The word limbic comes from the Latin term limbus, which means 'contour'. It is a set of brain structures located in the upper part of the brainstem and below the cortex. The structures of the limbic system participate in the process of generating many of our emotions and motivations, particularly those that are related to survival. Such emotions include fear, anger and others. It is also a key structure for the proper functioning of feelings of pleasure.
Some limbic system structures such as the hippocampus and the amygdala are involved in memory. The amygdala is responsible for determining which memories are stored and where they are stored in the brain. It is believed that this determination is based on the amount of emotional response an event can invoke. The hippocampus sends the memories to the appropriate part of the cerebral hemisphere for long-term storage and retrieves them when necessary. Damage to this area of the brain can cause the inability to form new memories.
- 1 Origin of the limbic system
- 2 Anatomy of the limbic system
- 3 Central and peripheral neural components of emotion
Limbic system origin
In 1878, the French neurologist Paul Broca observed that on the medial surface of the brain there was a whole differentiated set of cortical areas with an oval shape. Broca defined the limbic lobe as the cortical tissue that forms an edge over the medial face of the hemispheres, around the brainstem and corpus callosum. He made a structural description of the medial cortex when he introduced the concept of the limbic lobe.
Subsequently, these limbic lobe structures (described by Broca) along with the olfactory bulbs became known as the encephalon; that is to say, the olfactory brain is spoken, given that these structures were thought to have a great weight in the perception of odors and in the control of behaviors guided by smell.
An emotional system
The American J. Papez described that the bark of the Rhinocephalus was the only cortex that had demonstrated anatomical connections with the hypothalamus (key structure in the expression of emotions). Thus, Papez proposed that the fundamental role of these structures was the emotional information processing.
Papez described an emotional anatomical system located in the medial wall of the hemispheres, which interconnected the cortex and the hypothalamus.
In 1952, the American Paul MacLean, to ignore the concept of olfactory brain and link his proposal with Papez's emotional theory, spoke of visceral brain. In this way, MacLean used the term limbic system to refer to the limbic cortex and its connections with the brain stem, while proposing that this system would participate in the control and elaboration of emotions, and not so much in the smell system.
In 1952, MacLean introduced the concept of "limbic system" into the literature, recovering the limbic term described above for Broca.
Anatomy of the limbic system
Anatomically, the limbic system is composed of a series of cortical and subcortical structures interconnected with direct projections on the hypothalamus and the brainstem.
- Amygdala: It is a small almond-shaped structure involved in emotional responses, hormonal secretions and memory. The amygdala is responsible for the conditioning of fear or the process of associative learning through which we learn to fear something.
- Circumvolution of the cingulum: It is a fold in the brain related to sensory information related to emotions and the regulation of aggressive behavior.
- Fornix: It is an arch, a band of axons of white matter (nerve fibers) that connect the hippocampus with the hypothalamus.
- Hippocampus: This is a small bump that acts in memory by sending memories to the appropriate part of the cerebral hemisphere for long-term storage and recovering them when necessary.
- Hypothalamus: approximately the size of a pearl, this structure directs a multitude of important functions. It wakes us up in the morning and makes the adrenaline flow. The hypothalamus is also an important emotional center that controls the molecules that make us feel euphoric, angry or unhappy.
- Olfactory bark: receives sensory information from the olfactory bulb and participates in the identification of odors.
- Thalamus: a large dual lobular mass of gray matter cells that relays sensory signals to and from the spinal cord and brain.
The limbic lobe It is composed of the circumvolution of the cingulum, the para-hippocampal gyrus, the hippocampal formation, the olfactory cortex and various subcortical structures.
Subcortical structuresComponents of the limbic system are: the hypothalamus, the septum, the epithalamus, the habenula, the anterior and dorsomedial nucleus of the thalamus, part of the basal ganglia and the tonsil.
The limbic system in emotional regulation
Broca's limbic lobe structures were intimately related to emotions. Currently, there is experimental evidence that highlights the fact that some of the limbic areas are involved in emotional functions, but there are others that are more important in the cognitive processing and not so much in the processing of emotional information.
MacLean considered that the limbic system could be defined anatomically from its connections with the hypothalamus, but today it has been observed that the hypothalamus is connected to virtually all levels of the nervous system.
The same researcher described that Broca's limbic lobe structures could be identified according to the control they exerted over the autonomic nervous system. In this regard, although it is true that some areas of the limbic system have an important role in the control of the autonomic nervous system, there are also nuclei in the brain stem with a very important autonomic regulation.
Currently, we can dismiss the consideration, established by pioneering theories in the study of emotions, of the limbic system as an emotional brain.
Central and peripheral neural components of emotion
At present, it is clear that the peripheral component of emotions includes the hypothalamus, while the central component comprises the cerebral cortex, especially the cingulate cortex and the prefrontal cortex (ventral, medial and orbital areas). In between the two components is the amygdala, which seems to coordinate conscious experience and peripheral expressions of emotions.
Within the emotional processing there are two components, one of central character and the other peripheral, both coordinated by the tonsil.
Although the limbic system is composed of widely interconnected structures, they exercise varied functions. In recent years, many researchers in the field of emotions highlight the idea that probably multiple emotional information processing systems coexist in the human brain.
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