The human brain is one of the most complex structures in the entire universe and still poses great puzzles to researchers. One part of this marvel of nature is the so-called amygdala, whose function has been vital to human survival since time immemorial.
What is the amygdala?
The amygdala is part of the human brain. The name comes from the Greek word for almond, amygdale, and was chosen because the two areas in question in the brain resemble two almond kernels. Therefore, they are less commonly referred to as the corpus amygdaloideum, or almond nuclear complex.
Anatomy and structure
The amygdala is part of the limbic system and is located in the anterior part of the temporal lobe. It consists of two similar nuclear areas located just anterior to the hippocampus, near the tail of the caudate nucleus and the inferior horn of the lateral ventricle. Since the amygdala also includes a small piece of the cerebral cortex, it is effectively a transitional area between the cerebral cortex and the core area of the human brain. The amygdala can be divided into three different zones: the basolateral complex, in which the three nuclei nucleus lateralis, nucleus basalis as well as nucleus basolateralis are located, the centromedial nucleus group with the nucleus centralis and nucleus medialis, and the cortical nucleus group, in which the nucleus corticalis is located. These nuclei are interconnected and interact with each other through a multitude of nerve fibers. In addition, the amygdala is also connected to the brainstem, the hypothalamus located in the diencephalon, and the basal ganglia.
Function and tasks
The main function of the amygdala is the generation and processing of anxiety, as well as the associated physical reactions. For example, it shows itself responsible for the fact that in dangerous situations the heartbeat increases dramatically and the breath stops. The typical wincing that occurs when a fearful or frightening situation suddenly arises is also triggered by the connection between the amygdala and the brain’s motor system. Through its linkage with the hypothalamus, it is also responsible for signaling to the latter the need to increase adrenaline production in the adrenal glands. Adrenaline prepares the body for a fight or flight from imminent danger. Processes not needed for this, such as digestion, are then briefly curtailed to provide energy for more important functions such as the cardiovascular system. At the same time, the amygdala processes the emotions developed by fear and ensures that information or events experienced are linked to emotions. This also plays an important role in the emotional classification of facial expressions. Thus, the amygdala processes external stimuli and the resulting physical reactions. The amygdala can also amplify certain emotions such as fear or anger and is involved in the (re)recognition of previously experienced situations. Traumatic experiences are stored in the amygdala and constantly compared with current situations. When a similar situation occurs, the physical and hormonal reactions just described are then triggered. Without the amygdala, neither fear nor aggression can develop and dangers can no longer be assessed, one of the most important survival strategies of human evolution. Even though this is admittedly becoming less and less important in the modern world, since today’s life often has little in common with the struggle for survival of earlier times.
Diseases
The amygdala plays a major role in a variety of anxiety and panic disorders. For example, many phobias, i.e. fears of certain things or situations, originate from malfunctions of the amygdala, which mistakenly perceives these things as a threat and sends corresponding signals to the organism. In this context, however, a generalization of the situations perceived as dangerous may occur, so that the physical and mental symptoms of anxiety, such as nausea or panic, appear completely unexpectedly and suddenly. This condition is triggered by an overstimulation of the amygdala, which then almost indiscriminately considers situations to be dangerous that, objectively speaking, are not, and causes those affected to experience anxiety for no apparent reason. This is because the symptoms are often triggered unconsciously, i.e. without any actual perceptible memory of the traumatic event.The situations that lead to the triggering of the panic reactions are referred to in technical language as triggers. A lack of functioning of the amygdala can also lead to a variety of other symptoms. These include memory disorders, autism, narcolepsy, depression or post-traumatic stress disorder. In the extremely rare and genetic Urbach-Wiethe syndrome, the amygdala is calcified. Affected individuals therefore have great difficulty in understanding the emotional meaning of facial expressions, especially when these express fear. In general, they can do little with the emotion of fear. Thus, they are neither able to feel fear, nor to describe it, nor to recognize it in other people. This lack of anxiety often makes it difficult for them to make the right decisions in critical or dangerous situations, which is a great danger for them. At a time when mental illnesses are on the rise in the western world, detailed research into the amygdala is playing an increasingly important role. As a region in the human brain essential for the development and processing of anxiety, it occupies a key role in the search for new and effective treatments for anxiety disorders and various forms of depression.
