Semantic memory

The semantic memory belongs to the declarative memory and contains objective facts about the world that are coded via certain interconnections of the synapses in the temporal lobe. The hippocampus, among other things, is involved in expanding semantic memory. In forms of amnesia, semantic memory can be disturbed.

What is semantic memory?

The semantics is the theory of meaning. Part of long-term memory is known as semantic memory. This long-term memory is the permanent storage system of the brain and consists of the main groups of declarative and procedural memory.

The neocortex of the brain is primarily involved in declarative memory. The declarative memory is the knowledge memory in which both factually objective world knowledge and personal knowledge of experienced events are stored. All facts and events that a person can consciously reproduce sit in the declarative memory. The declarative memory consists of an episodic and a semantic part. Its semantic part contains a person's world knowledge. These are objective facts that are independent of the person.

The temporal lobe of the neocortex is particularly involved in semantic memory. The subcortical regions of the brain are also relevant for storage processes in this part of the memory. All learning processes and memory processes are based on neural learning processes and are based on the formation of various neural switching patterns.

Function & task

The human long-term memory is not a unit, but corresponds to several storage capacities and different information stores. There is no known limitation of capacity in relation to long-term memory. Four different processes play a role for long-term memory: learning and encoding to re-store information, remembering and retrieving to become aware of certain memory contents, consolidation and retention to consolidate information through repeated retrieval and forgetting in the sense of a disintegration of certain memory contents.

In order to transfer new content into the long-term memory and to preserve it, information from the working memory (short-term memory) must be consciously called up as often as possible. How deeply they are anchored in long-term memory depends on their meaning, their emotional content and the connection to existing content.

In the declarative part of the long-term memory (and thus in the knowledge memory) facts and events are stored that the person can consciously reproduce. The semantic memory contains the world knowledge in the sense of the objective general facts.

Since this article is a factual knowledge article, the reader saves the connections to semantic memory presented in the semantic memory. If, on the other hand, facts from one's own life are to be filed, they wander into episodic memory. The name of family members is in a different place in declarative memory than knowledge about general world connections.

The neocortex is involved in declarative memory. While episodic memory is built on the right frontal lobe and temporal cortex, the basis of semantic memory is almost exclusively the temporal lobe. Subcortical regions contribute to storage, for example the limbic system, the medial system of the temporal lobe and the hippocampus. These storage processes are summarized in the Papez neuron circle. The content of the memory corresponds to various connections between individual nerve cells. In the case of semantic memory, each connection encodes a specific meaning. We often talk about the synaptic efficiency of neural networks.

Around 100 billion nerve cells are located between 100 and 500 billion different synapses. Synaptic plasticity is the crucial element. This term refers to the adaptability of the synapses, which can change their anatomical shape. Transmission properties between the synapses are also permanently adapted through the formation and breakdown of synapses and thus memory contents.

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Illnesses & ailments

One of the most well-known forms of memory impairment is amnesia. In addition to accidents with a traumatic brain injury, amnesia can be triggered by diseases such as epilepsy, meningitis or encephalitis. The same applies to a stroke, hypoxia, poisoning or dementia.

Amnesia based on traumatic experiences in which certain memory contents are simply blocked is to be distinguished from physically caused amnesia. In the case of amnesia of physical origin, brain damage is usually the primary triggering factor in the memory impairment. Depending on the location of the damage, the loss of memory can be limited to a limited part of the memory, for example. For example, some patients only suffer from short-term memory amnesia, while others are affected by generalized short-term and long-term memory amnesia. Theoretically, amnesia can only affect the semantic memory and thus only make people forget the memory of factual information, but not the names of family members.

Another form of amnesia does not relate to actual memory loss, but rather the inability to store new information in long-term memory. This type of amnesia often occurs when the medial temporal lobe system or the hippocampus, including its adjacent areas, are affected by injuries. A frequently cited case in this context is the amnesia of a patient, the the hippocampus was removed therapeutically because of severe epilepsy. After the operation, the patient no longer had epilepsy, but had severe anterograde amnesia. For this reason he was no longer able to remember anything new. His previously acquired memory contents, however, were retained.