Semantic Memory: Function, Tasks, Role & Diseases

Semantic memory is part of declarative memory and contains objective facts about the world encoded by specific circuitry of synapses in the temporal lobe. The hippocampus, among others, is involved in the expansion of semantic memory. In forms of amnesia, semantic memory may be impaired.

What is semantic memory?

Semantics is the theory of meaning. Semantic memory is known as a part of long-term memory. Semantics is the theory of meaning. As semantic memory is known a part of the long-term memory. This long-term memory is the permanent storage system of the brain and consists of the supersets of declarative and procedural memory. Declarative memory primarily involves the neocortex of the brain. The declarative memory is the knowledge memory, in which both factual objective world knowledge and personal knowledge about experienced events are stored. The declarative memory thus contains all facts and events that a person can consciously reproduce. The declarative memory consists of an episodic and a semantic part. Its semantic part contains a person’s knowledge of the world. 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 memory. All learning and memory processes have neuronal learning processes as their basis and rely on the formation of various neuronal switching patterns.

Function and task

Human long-term memory is not a unit, but corresponds to several storage capacities and different information stores. A limitation of capacity is not known related to long-term memory. Four different processes play a role for long-term memory: learning and encoding for new storage of information, remembering and retrieval for awareness of certain memory contents, consolidation and retention for information consolidation by repeated retrievals, and forgetting in the sense of decay of certain memory contents. In order to transfer new content to long-term memory and retain it, information from working memory (short-term memory) must be consciously recalled as often as possible. How deeply they are anchored in long-term memory depends on their meaning, their emotional content and the link to already existing content. In the declarative part of long-term memory (and thus in knowledge memory), facts and events are stored that people can consciously recall. The semantic memory contains the world knowledge in the sense of the objectively general facts. Since it concerns for instance with this article a factual knowledge article, the reader stores the presented connections to the semantic memory in the semantic memory. If, on the other hand, facts from one’s own life are to be stored, they move into episodic memory. Thus, the name of family members sits in a different place in declarative memory than knowledge about general world connections. Involved in declarative memory is the neocortex. 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, such as the limbic system, the medial system of the temporal lobe, and the hippocampus. These memory processes are summarized in the Papez neuron circuit. The memory content thus corresponds to various connections of individual neurons. Thus, in the case of semantic memory, each connection encodes a specific meaning. This is often referred to as the synaptic efficiency of neuronal networks. About 100 billion neurons are located between 100 and 500 trillion different synapses. Synaptic plasticity is the crucial element. This term refers to the adaptability of synapses, which can change their anatomical shape. Transmission properties between synapses are furthermore permanently adapted by new formation and degradation processes of synapses, and thus memory contents.

Diseases and disorders

One of the best-known forms of memory impairment is amnesia.Amnesia can be triggered, for example, by diseases such as epilepsy, meningitis or encephalitis, in addition to accidents involving traumatic brain injury. The same applies to a stroke, hypoxia, poisoning or dementia. Amnesia following traumatic experiences, in which certain memory contents are merely blocked, must be distinguished from amnesia of physical cause. In the case of amnesia of physical cause, brain damage is usually the primary triggering factor of the memory impairment. Depending on the location of the damage, for example, the amnesia may be restricted to a limited memory part. Thus, some patients suffer from amnesia of short-term memory only, while others are affected by generalized amnesia of short-term and long-term memory. Theoretically, amnesia can also affect exclusively semantic memory, thus causing forgetting only the memory of factual information, but not the names of family members. Another form of amnesia refers not to actual memory loss but to 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 injury. A frequently cited case in this context is the amnesia of a patient who has been

hippocampus was therapeutically removed due to severe epilepsy. After surgery, the patient no longer suffered from epilepsy but struggled with severe anterograde amnesia. For this reason, he was no longer able to remember new things. In contrast, his previously acquired memory contents remained intact.