Memory is an aspect of cognitive functioning that involves the encoding, storage, consolidation and recall of experiences, learning and recognition.
The process of memory formation is afforded by the ability of the brain to make basic structural changes within the synapses (the junction between neurons).
Therefore, the formation of a specific memory occurs rapidly, but the evolution of a memory is often an ongoing process.
Memory processes have been shown to be stabilized and enhanced (sped up and/or integrated) by nocturnal sleep and even daytime naps.
Acquisition refers to the introduction of new information into the brain.
Consolidation represents the processes by which a memory becomes stable.
It is generally assumed that long-term memory consolidation involves interactions among multiple brain systems, modulated by various neurotransmitters and neurohormones.
Although we acknowledge the likely involvement of various neuromodulators in these phenomena, we focus on the hormone cortisol, which is known to exert influence on many of the brain systems involved in memory.These changes create biochemical associations with the events being recorded. Although memories are encoded very quickly in the brain (in milliseconds), they are also being changed during consolidation.The consolidation of memories can take as long as years but when it is done, memories are stable and resistant to all but the most powerful change agents (such as a head injury).In this article we propose an approach to dreaming that focuses on the relationship between sleep and memory.We suggest that dreams reflect a biological process of long-term memory consolidation, serving to strengthen the neural traces of recent events, to integrate these new traces with older memories and previously stored knowledge, and to maintain the stability of existing memory representations in the face of subsequent experience (Winson 1985, 2002, 2004; Kali and Dayan 2004).Beyond instantaneous encoding of memories, the other processes of memory formation require sleep.