Although a number of neurotransmitters and neurohormones are likely involved, we focus our attention in particular on the stress hormone , which has widespread effects on memory during waking life through its impact on many of the critical brain structures implicated in memory function.Our hypothesis, briefly stated, is that variations in cortisol (and other neurotransmitters) determine the functional status of hippocampal ↔ neocortical circuits, thereby influencing the memory consolidation processes that transpire during sleep."Consolidation" is a term that is bandied about a lot in recent memory research. Initially, information is thought to be encoded as patterns of neural activity — cells "talking" to each other.Later, the information is coded in more persistent molecular or structural formats (e.g., the formation of new synapses).Therefore, the formation of a specific memory occurs rapidly, but the evolution of a memory is often an ongoing process.
We propose that the characteristics of dreams are best understood in the context of this neuromodulatory impact on the brain systems involved in memory consolidation.Researchers found that the changes to a cell that occurred in response to an initial stimulation lasted some three to five minutes and disappeared within five to 10 minutes.If the cell was stimulated four times over the course of an hour, however, the synapse would actually split and new synapses would form, producing a (presumably) permanent change.Memory is essentially the capacity for storing and retrieving information.Three processes are involved in memory: encoding, storage, and retrieval.
In 1801, David Hartley first postulated that dreaming altered the associative planetary links within the brain during dreaming periods of dreams.