The ammonic horn is a part of the brain. It is located in the hippocampus and is located in the curled cortical structure there. It has an important role in the learning process.
What is the ammonium horn?
Ammon’s horn is medically referred to as cornu ammonis. In some sources, it is also titled the hippocampus proprius. The ammonic horn forms part of the internal structure of the hippocampus. This is mostly located in the inner margin of the temporal lobe. This area is also called the temporal lobe. The hippocampus is responsible for learning, emotions and memory formation. It is considered part of the limbic system. The ammonic horn contributes a significant part to the learning process. It forms the basis for the formation of long-term memories. The hippocampus contains the archicortex. This has three layers and is considered the hippocampal formation. The three layers are divided into the dentate gyrus, the Ammon’s horn, and the subiculum. The dentate gyrus is the major afferent system in the hippocampus. The subiculum forms much of the efferent system of the hippocampus. Therefore, most information in the hippocampus flows through the dentate gyrus as well as the subiculum. The ammonic horn can be differentiated into four regions based on the different tissue structure. These are called CA1, CA2, CA3 as well as CA4.
Anatomy and structure
The hippocampus is located on the inner surface of the temporal lobes. It visually has the shape of the body of a seahorse without the head. Once a frontal section is made in the lower part of the tail, the three layers, the dentate gyrus, the ammonic horn, and the subiculum, become visible. In this area, the tissue has a very characteristic structure. It is called the rolled cortical structure. This microscopic archicortex structure is divided into three layers. The area of the ammonium horn is divided into different fields of cytoarchitectonic structure. These are four sectors named CA1-CA4. The field CA1 contains very many small pyramidal cells. Field CA2 contains particularly large pyramidal cells. These are densely packed. The same large cells are also found in field CA3. Here, however, they are loosely arranged. In field CA4, the distances between the cells are even larger. The cell-rich layer is called the stratum pyramidale. The dendrites of the pyramidal cells radiate into the stratum radiatum. From there, they continue to enter the stratum lacunosum and the stratum moleculare.
Function and tasks
The ammonium horn has an important role in memory consolidation. This involves learning or learning processes. This refers to the process that transfers information from short-term memory to long-term memory. This takes a time window of several days to months. Only then are the memories also permanently stored in the memory. In the ammonium horn, the so-called long-term potentiation takes place. This serves as the basis for all learning and memory processes. This applies mainly to long-term memories and knowledge formation in the declarative memory. Here, information such as facts and events are stored. This includes factual contexts as well as spatial conditions. In addition, the ammonium horn is also involved in the formation of implicit memory. These memory contents include courses of action, habits, motor learning as well as emotional learning. The pyramidal cells in the ammonium horn are responsible for long-term potentiation. This only works if the potentiating impulses arrive at a sufficiently high speed. Otherwise the information is extinguished after a short time. Thus the ammonium horn is responsible for the prerequisite as well as for the formation of the memory contents. As described above, the ammonium horn is divided into four fields. The fields CA1-CA3 play an important role in operant conditioning. This involves the learning of specific stimulus-response patterns.
Diseases
Ammonium horn pyramidal cells are particularly susceptible to damage from alcohol abuse. Regular consumption of alcohol leads to an addictive disease after several years. In severe cases, this can lead to Wernicke’s encephalopathy or Korsakow’s syndrome. As a result of alcohol abuse, confabulation takes place in the patient. Sufferers can no longer access their own memories.For this reason, they think up answers to questions or whole stories. They consider their explanations to be true and logical. Nevertheless, it is a production of objectively false statements or narratives. Patients with the described disorders are unable to admit the absence of memories. Confabulation takes place as a consequence of the disease. The disturbance of memory is basically called amnesia. Anterograde and retrograde amnesia must be distinguished from each other. Anterograde amnesia results in no new memory formation. In retrograde amnesia, the memory contents that were formed before brain damage are no longer available. They are partially or completely erased. The ammonic horn plays an essential role in the formation of memory content. Impairments in its functioning lead to problems in long-term memory formation in particular. A lesion of the hippocampus as a result of circulatory disorders or due to brain inflammation lead to complete temporal as well as local disorientation in addition to the loss of memory capacity. Defects of the hippocampus have a relevance beyond the certain forms of memory disorders also in diseases like epilepsy. Ammon’s horn sclerosis is considered the most common neuropathological finding in temporal lobe epilepsy. This is a particular form of epilepsy.
