Semantic memory: functioning and associated disorders
Memory is a psychological concept in which we usually think as if it were one thing: the act of remembering what we dined yesterday seems to have the same nature as remembering what is the capital of Egypt or how are the steps of a choreography that we have been practicing. However, from the perspective of Psychology this is not so, since there are different types of memory.
For example, part of memory is not composed of concepts, but by emotions and patterns and movements. However, within the type of memory composed of verbalizable aspects of knowledge, which is called declarative memory, there is also a subdivision. On the one hand there is episodic memory, which is one that contains memories about narrative information from our past experiences (like what happened to us yesterday when going to buy bread), and on the other we find the semantic memory , in which we will focus on this article.
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What is semantic memory?
In short, semantic memory is the one that contains all the information related to the concepts by which we understand the world and to ourselves. That is to say, it is something like the store of concepts about everything we know: the name of the countries, the characteristics of the mammals, the history of the region in which we live, etc.
That is to say, that semantic memory makes it possible for us to understand the environment in which we find ourselves, and also to ourselves, since it allows us to reflect on our personal characteristics.
While being a type of declarative memory is composed of concepts , unlike episodic memory, it does not follow a narrative progression. The fact that Africa is a continent has nothing to do with an experience with a beginning, development and outcome, it is enough to know the term "Africa" and link it to a territory that we have been able to see on a map and that exists beyond that map, not just as part of an anecdote of our private life.
The information that contains the semantic memory can be understood as a pyramid of concepts; some of them are very general and are composed of other concepts, which in turn are formed by others, until they reach units of very basic and insignificant information because they are too specific.
So, it is a mental capacity that is expressed consciously and often voluntarily , for example, when we need to access relevant information to correctly answer an examination question (something that does not happen with emotional memory, or not to the same extent).
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Functions of semantic memory
All types of memory have a crucial importance and complement each other, but the case of semantic memory is special because thanks to it we are able to create the concepts needed to develop the language and to become able to think abstractly.
If non-declarative memory is useful at the time of directing our behavior from our learning and episodic memory allows us to understand the specific context in which we live and by what specific situations we have passed, semantics is what generates all those ideas that we need to build beliefs, expectations, objectives , etc.
Thus, this type of memory is closely linked to the ability to use language, which is nothing more than a system of symbols with an abstract meaning not linked to a specific place and time.
Parts of the brain involved
The differentiation between semantic memory and other types of memory is not simply theoretical: it is materially embodied in the brain.
For example, emotional memory is closely related to the activity performed by a part of the brain called the amygdala, while episodic memory is related to another structure called the hippocampus and the cerebral cortex.
Regarding semantic memory, it also depends in part on the hippocampus, but to a lesser extent than on episodic memory. It is believed that, in comparison to the episodic, the importance of the general activity of the cerebral cortex is greater .
As each type of memory has several brain structures more oriented to it than the others, this makes certain neurological pathologies also affect more than the rest.
In the case of semantic memory, this seems to be especially vulnerable to lesions in the prefrontal cortex, although alterations in the hippocampus also affect it much, as with the episodic.
However, in practice many pathologies that wear down our ability to remember concepts damage several areas of the brain at the same time. This is what happens for example with dementias; practically all of them play against this type of mental capacity, since they kill many neurons distributed throughout almost the whole brain (although more in some areas than in others).