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Declarative memory is the brain’s portion of long term memory dedicated to the storage of information about facts and events, complemented by the procedural memory, which stores information about how to do things. Information about how to ride a bicycle is stored in the procedural memory, while the personal memory of learning to ride a bike is found in the declarative memory, as are facts about the history of the bicycle. This aspect of the long term memory is complex and involves activity in multiple areas of the brain, with a focus on the hippocampus and prefrontal cortex.
This portion of the long term memory is sometimes referred to as explicit memory, and breaks down into two sub-components. One, the semantic memory, functions by storing factual data like dates, names, and so forth. This information is general to society and many people may store the same memories, such as the date of an important historic event. Capacity for semantic memory is very large, especially when people use memorizing tricks to help them store and recall information.
The other portion of the declarative memory stores episodic memories related to specific events in a person’s life. These memories are personal, rather than social, and can include good and bad events. Episodic memories include everything from birthday parties to flying on an airplane for the first time. The level of detail in each memory can vary, depending on how well it was encoded.
There can be some intersections between episodic and semantic memory, allowing the components of declarative memory to interact with each other. For example, a person may recall the date of a natural disaster, which is a piece of factual information, but could also remember the details of the disaster, which are episodic memories. Autobiographical memories of this nature that contain a mixture between facts and personal experiences can sometimes be very vivid.
Errors with the function of declarative memory can occur for a variety of reasons. Stress can impair memory formation, as can brain damage, and it is also possible to experience memory loss, where memories are successfully encoded, but become unreachable due to lesions in the brain. Sometimes problems with memories can be an early warning sign of degenerative cognitive disorders and other issues, like damage after a seizure or fall. Studies on the way declarative memory works in humans and nonhuman animals are used to explore what happens when it goes wrong, and to learn more about the precise mechanics of memory formation, storage, and retrieval.