Long Term Memory (LTM) stores information that is received from short term memory for an indefinite period of time. Obviously, no one remembers every single fact and event that occurs over a lifetime, which leads to the notion that memories are categorized for retrieval based on perceived significance. As information enters LTM, it is stored in the cerebral cortex, in specific locations, based on the type of memory being stored.
LTM is divided into two general categories: declarative (explicit) and procedural (implicit). Declarative memory is thought to be largely related to the conscious mind since these memories can be consciously retrieved and ‘declared’ as facts and events, as responses to questions such as ‘what’, ‘where’ , and ‘when’.
Declarative memory is further subdivided into episodic and semantic. Episodic memory holds the details of specific, personal experiences, or ‘episodes’, such as remembering your first kiss, your first day at school, an illness, a birthday party, etc. The hippocampus integrates the initial processing of declarative memories, which occurs in the medial temporal lobe, with several areas of the parahippocampal region, that processes the actual facts about these memories. Semantic memory stores different types of general knowledge and facts that are not necessarily related to personal experiences, such as the meanings of words, the sounds of a language, people’s faces, material learned for taking an exam, knowing that grass is green, and historical facts. Less is known about where semantic data is processed and stored however scientists have found that certain networks in the cerebral cortex are dedicated to processing specific categories of information.
Procedural memory stores events that involve the acquisition all information needed to carry out any given procedure, or the ‘how to’. These memories are accessed at the unconscious level, hence are referred to as implicit (or inactive) knowledge. Information stored in procedural memory pertains to learning experiences required for performing various tasks. It also has the ability to store the strategies as sequential events that are needed to carry out tasks, such as riding a bike, using a fork, rock climbing, developing a habit, and how to form a coherent sentence. This type of information is processed by the basal ganglia and cerebellum, the latter which is specifically related to motor tasks and coordination (like lerning to drive a car with a manuel transmission).
Although LTM is able to store unlimited information, it is less able to retain smaller chunks of information and distinguish them from one another.
Tulving, E. (1972). Episodic and semantic memory. In E. Tulving & W. Donaldson (Eds.), Organization of Memory, (pp. 381–403). New York: Academic Press.
Thomas and Aronow (2016)