Long-term memory (LTM) is memory that lasts from days to years. It differs from working memory and short-term memory, which both last from seconds to hours. Biologically, short-term memory is a temporary potentiation of neural connections that can become long-term memory through the process of memory consolidation.
As long-term memory is subject to fading in the natural forgetting process,
several recalls/retrievals of memory may be needed for long-term memories to
last for years. Individual retrievals can take place in increasing intervals
in accordance with the principle of spaced repetition.
Sleep is considered a necessary factor for establishing well-organized
long-term memories.
