The amygdala, otherwise known as the amygdala, is a small collection of gray matter. It is about him that we will talk. The amygdala (functions, structure, location and its defeat) has been studied by many scientists. However, we still do not know everything about him. Nevertheless, enough information has already been accumulated, which is presented in this article. Of course, we will present only the basic facts related to such a topic as the amygdala of the brain.
Amygdala at a glance
It is round and is located inside each of the hemispheres of the brain (that is, there are only two of them). Its fibers are mostly connected to the organs of smell. However, a number of them also fit the hypothalamus. Today it is obvious that the functions of the amygdala have a certain relation to the mood of a person, to the feelings that he experiences. In addition, it is possible that they also refer to the memory of events that occurred recently.
Connection of the amygdala with other parts of the CNS
It should be noted that the amygdala has very good"connections". If the scalpel, probe, or illness damages it, or if it is stimulated during the experiment, significant emotional shifts are observed. Note that the amygdala is very well located and connected with other parts of the nervous system. Because of this, it acts as the center of regulation of our emotions. It is here that all signals come from the primary sensory and motor cortex, from the occipital and parietal lobes of the brain, as well as from part of the associative cortex. Thus, it is one of the main feeling centers of our brain. The tonsils are connected to all its parts.
Structure and location of the amygdala
It is a structure of the telencephalon, which has a rounded shape. The amygdala belongs to the basal ganglia located in the cerebral hemispheres. It belongs to the limbic system (its subcortical part).
There are two tonsils in the brain, one in each of the two hemispheres. The amygdala is located in the white matter of the brain, inside its temporal lobe. It is located anterior to the apex of the inferior horn of the lateral ventricle. The amygdaloid bodies of the brain are posterior to the temporal pole by about 1.5-2 centimeters. They border the hippocampus.
Three groups of nuclei are included in their composition. The first is basolateral, which refers to the cerebral cortex. The second group is cortico-medial. It belongs to the olfactory system. The third is the central one, which is associated with the nuclei of the brain stem (responsible for controllingautonomic functions of our body), as well as with the hypothalamus.
Meaning of the amygdala
The amygdala is a very important part of the limbic system of the human brain. As a result of its destruction, aggressive behavior or a lethargic, apathetic state is observed. The amygdala of the brain, through connections with the hypothalamus, influences both reproductive behavior and the endocrine system. The neurons in them are diverse in function, form, and neurochemical processes occurring in them.
Among the functions of the tonsils, one can note the provision of defensive behavior, emotional, motor, vegetative reactions, as well as the motivation of conditioned reflex behavior. Undoubtedly, these structures determine the mood of a person, his instincts, feelings.
Polysensory nuclei
Electrical activity of the amygdala is characterized by different frequency and different amplitude fluctuations. Background rhythms correlate with heart contractions, breathing rhythm. The tonsils are able to respond to skin, olfactory, interoceptive, auditory, visual stimuli. At the same time, these irritations cause changes in the activity of each of the amygdala nuclei. In other words, these nuclei are polysensory. Their reaction to external stimuli, as a rule, lasts up to 85 ms. This is significantly less than the reaction to the same irritation, characteristic of the new cortex.
It should be noted that the spontaneous activity of neurons is very well expressed. It canslow down or enhance sensory stimuli. A significant part of neurons is polysensory and polymodal and synchronizes with the theta rhythm.
Consequences of irritation of the tonsil nuclei
What happens when the nuclei of the amygdala are irritated? Such an impact will lead to a pronounced parasympathetic effect on the activity of the respiratory and cardiovascular systems. In addition, blood pressure will decrease (in rare cases, on the contrary, it will increase). The heart rate will slow down. There will be extrasystoles and arrhythmias. The heart tone may not change. The decrease in heart rate observed when exposed to the amygdala is characterized by a long latent period. In addition, it has a long aftereffect. Respiratory depression is also observed when the tonsil nuclei are irritated, sometimes a cough reaction occurs.
If the amygdala is artificially activated, there will be reactions of chewing, licking, sniffing, salivation, swallowing; moreover, these effects occur with a significant latent period (up to 30-45 seconds after irritation). The various effects that are observed in this case arise due to the connection with the hypothalamus, which is the regulator of the work of various internal organs.
The amygdala is also involved in the formation of memory, which is associated with events that have an emotional coloring. Violations in his work cause various types of pathological fear, as well as other emotional disorders.
Communication with visual analyzers
The connection of the tonsils with visual analyzers is carried out mainly through the cortex, located in the region of the cranial fossa (posterior). Through this connection, the amygdala influences information processing in the arsenal and visual structures. There are several mechanisms for this effect. We propose to consider them in more detail.
One of these mechanisms is a kind of "coloring" of incoming visual information. It occurs due to the presence of its own high-energy structures. One or another emotional background is superimposed on the information that goes to the cortex through visual radiation. Interestingly, if the tonsils are oversaturated with negative information at this moment, even a very funny story will not be able to cheer up a person, since the emotional background will not be prepared to analyze it.
In addition, the emotional background associated with tonsils has an impact on the human body as a whole. For example, the information that these structures return and which is then processed in programs makes us switch, say, from reading a book to contemplating nature, creating this or that mood. After all, in the absence of mood, we will not read a book, even the most interesting one.
Amygdala lesions in animals
Their damage in animals leads to the fact that the autonomic nervous system becomes less capable of implementing and organizing behavioral responses. This can lead to the disappearance of fear,hypersexuality, sedation, as well as inability to aggression and rage. Animals with an affected amygdala become very gullible. Monkeys, for example, approach the viper without fear, which usually causes them to flee, to be terrified. Apparently, the total defeat of the amygdala leads to the disappearance of some unconditioned reflexes present from birth, the action of which realizes the memory of imminent danger.
Statmin and its meaning
In many animals, especially mammals, fear is one of the strongest emotions. Scientists have proven that the statmin protein is responsible for the development of acquired types of fear and for the work of congenital ones. Its highest concentration is observed just in the amygdala. For the purposes of the experiment, scientists blocked the gene that is responsible for the production of statmin in experimental mice. What did it lead to? Let's find out.
Mice results
They began to ignore any danger, even in cases where the mice instinctively feel it. For example, they ran through the open areas of labyrinths, despite the fact that their relatives usually stay in places that are safer from their point of view (they prefer tight nooks and crannies in which they are hidden from prying eyes).
One more example. Ordinary mice froze in horror at the repetition of a sound accompanied by an electric shock the day before. Mice deprived of statmin perceived it as a normal sound. The lack of a "fear gene" at the physiological level led to the fact thatlong-term synaptic connections existing between neurons turned out to be weakened (it is believed that they provide memorization). The greatest weakening was observed in those parts of the nerve networks that go to the tonsils.
Experimental mice retained the ability to learn. For example, they memorized the path through the maze, found once, no worse than ordinary mice.
