What Is the Structure of the Limbic System?

The limbic system refers to the general term for the brain tissues evolved from the ancient cortex and old cortex in the central nervous system of higher vertebrates, as well as the collective name of the neural structures and nucleus groups closely related to these tissues. The ancient cortex and the old cortex are the basic structures separated by the new cortex. The important components of the limbic system include hippocampal structure, para hippocampal and entorhinal areas, dentate gyrus, cingulate gyrus, papillary body, and amygdala. The above structures are interconnected through the Papez loop and have extensive connections with other brain structures (neocortex, thalamus, and brain stem), so the role of the limbic system is to make the midbrain, mesencephalon, and neocortex Information exchange takes place. Through the connection with the hypothalamus and the autonomic nervous system, the limbic system participates in mediating instincts and emotional behaviors, and its role is to survive and sustain species. In addition, the hippocampal structure also plays a prominent role in the learning process and memory. Therefore, if the hippocampal structure or the structure with which it is functionally damaged is damaged, it leads to amnestic syndrome. Different lesions cause different forms of memory impairment.

The limbic system refers to the general term for the brain tissues evolved from the ancient cortex and old cortex in the central nervous system of higher vertebrates, as well as the collective name of the neural structures and nucleus groups closely related to these tissues. The ancient cortex and the old cortex are the basic structures separated by the new cortex. The important components of the limbic system include hippocampal structure, para hippocampal and entorhinal areas, dentate gyrus, cingulate gyrus, papillary body, and amygdala. The above structures are interconnected through the Papez loop and have extensive connections with other brain structures (neocortex, thalamus, and brain stem), so the role of the limbic system is to make the midbrain, mesencephalon, and neocortex Information exchange takes place. Through the connection with the hypothalamus and the autonomic nervous system, the limbic system participates in mediating instincts and emotional behaviors, and its role is to survive and sustain species. In addition, the hippocampal structure also plays a prominent role in the learning process and memory. Therefore, if the hippocampal structure or the structure with which it is functionally damaged is damaged, it leads to amnestic syndrome. Different lesions cause different forms of memory impairment.

Chinese scientific name

Limbic system

boundary

animal world

Features

Regulate visceral activity and affect mood

Edge originated from

Latin "limbus"

Edge system functions

1. Regulate visceral activity

2. Regulate sensory information in the central nervous system

In lower vertebrates, the hippocampal structure of the brain is able to accept various sensory stimuli. In higher mammals, physical, auditory, and visual sensations can be introduced into the hippocampus; stimulation of the anterior hypothalamic area, cingulate gyrus, and other parts of the limbic system can increase the pain threshold; stimulation of the amygdala can make the geniculate body of the thalamus Auditory information is suppressed.

3. Affect or generate emotions

Damage to the amygdala, hippocampus, preoptic region, fornix, olfactory nodules and compartments of monkeys, cats, dogs and other animals can cause animals to appear "false anger" reactions or "anger behaviors". Studies have also shown that if the cingulate is only damaged without damage to the neocortex of the brain, the animal's emotional response is often weakened or less likely to occur. The threshold of anger rises and there is a symptom of "social apathy" or "lost fear". At this time, the animals are indifferent to the harmful stimuli that must be usually avoided.

After the cat's amygdala was excised, there was hypersexuality and increased sexual response related to emotional responses. Removal of the amygdaloid nucleus of a macaque monkey can change its behavior from a ruler to a slave in the social life. Clinical studies have shown that after damaging a wide area of the limbic system, patients are prone to anger and show strong emotional reactions in social situations. This is also very similar to the experimental results obtained using animals.

4. Cause sleep activity

The posterior orbital gyrus, paraolfactory cortex, preoptic region, and anterior hypothalamus in the limbic system are sites related to sleep activity. These sites have been collectively referred to as basal forebrain by some scholars. When this brain region was stimulated with an electric current, the animal developed a sleep response. Cutting at this level below the brain area can eliminate insomnia in rats. Clinical observations have shown that patients with basal forebrain damage due to brain surgery also experience severe insomnia.

5. Participate in learning and memory activities

After the bilateral hippocampus is damaged, although the animals can establish operational conditioned reflexes and form differentiating reflex activities for different patterns, the number of required trainings is greatly increased. They are more difficult to establish reflex activities that are conditioned by time intervals, and they cannot cultivate conditioned delayed reflexes. For animals that already have delayed reflex activity, if their hippocampus is removed, delayed reflexes are not easy to appear, but other conditioned reflexes are still preserved. After the hippocampus is damaged, the animal's orientation response to new stimuli in the surrounding environment increases. When new stimuli recur, this response is difficult to subside. This indicates that the animal's "memory" ability is impaired. But for the conditioned reflexes that have been established, they do not disappear after the hippocampus is damaged, which indicates that the hippocampus is not the place to preserve traces of past experience. It is likely that during the learning process, various stimulus information left a temporary trace in the hippocampus. After its activity, the stimulus information entered long-term memory.

Limbic system limbic system related anatomy

In 1878, the French scholar Broca referred to the fairly constant curved brain around the mammalian brain stem as the "Legrandlobe limbigue". This is probably the source of the term "edge leaf". It is generally believed that it includes structures such as the cingulate gyrus, para hippocampal gyrus, hippocampal structure, compartment, and piriform leaf. Later, the concept of the marginal lobe gradually expanded to include areas similar to the cortex structure of the marginal lobe (frontal orbital gyrus, anterior part of the insular lobe, and temporal lobe), and some subcortical structures that are more closely related in function and connection (such as the septum , Amygdala, hypothalamus, superior thalamus, anterior nucleus of the thalamus, and medial area of the midbrain, etc.) are also linked together, called the limbic system. The limbic system cortex is an ancient part of biological evolution, including the more ancient heterogeneous cortex (such as the ancient cortex of the hippocampus and the dentate gyrus, compartments and amygdala) and the middle cortex (including the orbitofrontal cortex). Posterior, island leaf, temporal pole, cingulate gyrus, etc.). The blood supply of the limbic system cortex is very special. Its blood supply is supplied by both the perforating artery and the pia mater artery, and the venous return flows into both the superficial cerebral vein and the deep cerebral vein. It can be understood from the above anatomical structure that, in addition to advanced malignant tumors, tumors originating from this system have a certain affinity for the primordial cortical area of germline development, that is, after tumorigenesis, they are limited to the original cortical area, and to adjacent new ones. Cortical areas and deep medial structures such as the nucleus platinus, putamen, pale bulbs and inner capsule are not or rarely invaded. This growth mode of tumors provides a theoretical basis for neurosurgeons to radically remove tumors without damaging or rarely damaging these important structures. This concept is being valued.