Classification by information type
Long-term memory, the largest part of any model, can be divided into declarative (explicit) and procedural (implicit) memories.
Declarative memory requires conscious recall, in that some conscious process must call back the information. It is sometimes called explicit memory, since it consists of information that is explicitly stored and retrieved.
Declarative memory can be further sub-divided into semantic memory, which concerns facts taken independent of context; and episodic memory, which concerns information specific to a particular context, such as a time and place. Semantic memory allows the encoding of abstract knowledge about the world, such as "Paris is the capital of France". Episodic memory, on the other hand, is used for more personal memories, such as the sensations, emotions, and personal associations of a particular place or time. Autobiographical memory - memory for particular events within one's own life - is generally viewed as either equivalent to, or a subset of, episodic memory.
In contrast, procedural memory (or implicit memory) is not based on the conscious recall of information, but on an implicit learning of certain patterns about the world. It is revealed when we do better in a given task due only to repetition - no new explicit memories have been formed, but we are unconsciously accessing aspects of those previous experiences. Classical conditioning can be seen as a form of implicit memory, as can memory resulting from motor learning, which depends upon the cerebellum and basal ganglia.
Much of the current knowledge of memory has come from studying memory disorders, which are known collectively as amnesia. There are many sorts of amnesia, and by studying their different forms, it has become possible to observe apparent defects in individual sub-systems of the brain's memory systems, and thus hypothesize their function in the normally working brain.
The physiology of memory
Brain areas such as the mammillary bodies and hippocampus are thought to be involved in memory. It has been demonstrated that damage to these structures can result in impaired performance on certain memory tasks.
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