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.
We discuss the relationship between sleep, dreams, and memory, proposing that the content of dreams reflects aspects of memory consolidation taking place during the different stages of sleep.
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 dream reports after NREM awakenings led Foulkes and others to conclude that the stream of consciousness never ceases during sleep and that the brain engages in cognitive activity of some sort during all sleep stages (Antrobus 1990).
Typical REM and NREM dreams are quite distinct, particularly with respect to episodic memory content.
It is generally assumed that long-term memory consolidation involves interactions among multiple brain systems, modulated by various neurotransmitters and neurohormones.