Archicortex

Of the Archicortex is part of the cerebrum. Most of it is made up of the hippocampus. It consists of a very characteristic bark structure.

What is the archicortex?

Part of the cerebral cortex is called the archicortex. It is defined as the medial edge of the neocortex. The archicortex has a developmental background. The cerebrum is phylogenetically divided into paleocortex, striatum, archicortex and neocortex.

The archicortex is considered to be a stage between the paleocortex and the neocortex. The archicortex consists largely of the hippocampus. In addition, some of the structures around it are included. These are parts of the parahippocampal gyrus and the cingulate gyrus. The archicortex consists of a rolled-up bark structure. This has three layers and consists of the dentate gyrus, the ammonium cornu (Ammon's horn) and the subiculum. All three layers have the functions of learning and memory formation. Long-term potentiation in particular takes place here.

This forms the basis for storing long-term memories and learning courses of action, for example. The archicortex is referred to together with the paleocortex as the allocortex. This is compared to the six-layer neocortex. This leads to the fact that with appropriate detection techniques additional layers than those mentioned can be delimited in most of the allocortex areas.

Anatomy & structure

The archicortex consists of a microscopic structure and is mainly formed by the hippocampus, parts of the prahippocomapales gyrus and the cingulate gyrus.

The hippocampus consists of a rolled-up archicortex structure, also known as the cortex structure. It lies below the temporal lobe. These are located on the medial side of the lower horn of the lateral ventricle. The efferent fibers of the fornix are the vault, which serves as the roof of the III. Ventricle spanned from back to front. The cingulate gyrus is above the bar. This connects the right and left hemispheres. Together with the hippocampus, it forms the limbic system.

The archicortex consists of three layers. In them are the dentate gyrus, the ammonium cornea and the subiculum. They consist of pyramidal cells of different sizes. The three layers are divided into lamina molecularis (stratum molecularis), lamina pyramidalis (stratum pyramidale) and lamina multiformis (stratum oriens). In the first layer there are apical dendrites of the pyramidal cells, followed by the cell bodies of the pyramidal cells in the second layer. In the last layer are the basal dendrites of the pyramidal cells.

Function & tasks

The tasks of the archicortex include important functions of learning, thinking and emotional processing.

Essential processes of memory consolidation take place in the three layers of the archicortex. Learning and all related learning processes are associated with it. The process by which information is transferred from short-term memory to long-term memory takes place here. So that memories are permanently stored in the memory, the so-called long-term potentiation must take place.

This process takes several days to months and only takes place if the potentiating impulses are passed on at a sufficiently high speed. Long-term potentiation serves as the basis for all learning and memory processes. The archicortex is responsible for knowledge formation. This includes spatial conditions, factual knowledge, memories or conditioning processes. Knowledge of actions, habits or motor learning is formed here. The contents of the declarative memory as well as that of the implicit memory arise in the archicortex.

Emotion processing takes place in the limbic system. This includes the understanding of emotions and the associated experience of emotions. Processes that allow emotional expression and empathy to take place are controlled from this brain region. All learning processes around positive and negative emotions take place in the archicortex. This includes the recognition of danger as well as the feeling of pleasure. The satisfaction of needs is regulated in this part of the brain. The mood, the affect, the emotion and the feeling arise in the archicortex. This means that long-term as well as short-term emotional episodes occur through the processing of the stimuli in the limbic system.

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Diseases

Lesions and impairments of functional activity in the archicortex lead to far-reaching consequences in all learning processes as well as the processing of emotions. Various diseases, circulatory disorders, tumors or damage from accidents or as a result of surgical interventions can cause lesions.

Inflammation in the archicortex can lead to a loss of memory. In addition, those affected suffer from a temporal and spatial disorientation.

Amnesia is one of the most well-known memory disorders. A distinction must be made between anterograde and retrograde amnesia. Antero-straight amnesia does not allow any new memory formation. The retrograde amnesia leads to the fact that the existing memory contents are no longer available. They have been partially or completely deleted.

The pyramidal cells in the hippocampus are particularly vulnerable to damage from alcohol abuse. Diseases such as Wernicke's encephalopathy or Korsakov's syndrome are consequences of alcoholic diseases.They go hand in hand with confabulation. Missing memories of the sick are replaced by false statements and stories. Even answers to simple questions can no longer be given by patients if the pyramidal cells are damaged. In addition to the formation of long-term memory, lesions of the hippocampus are also relevant in diseases such as epilepsy.

Damage to the temporal lobe can lead to Klüver-Bucy syndrome. This condition leads to hyperoral as well as hypersexual behavior. Amygdala lesions lead to problems processing emotions. In particular, fear and fear stimuli can no longer be processed. These are important for self protection and survival.