We all know the old Ben Franklin quote, "Early to bed, early to rise, makes a man healthy, wealthy and wise." While I have not yet investigated the "wealthy" claim, Franklin was spot-on in the "healthy and wise" department; research has shown sleep to be a key contributor to optimal health and brain function.
Before we address sleep, here is a quick primer on some concepts regarding memory:
- Short-term memory, also known as "working memory," refers to memories that we use or refer to before discarding them or transferring them to long-term memory.
- Long-term memory refers to anything that happened more than a few minutes ago and breaks down into further categorizations, such as implicit/explicit and others. (See Posit Science, "Types of Memory" for a description of the different categories of memories.)
- Sleep benefits two specific forms of long-term memory: declarative (those memories that we can call up on-demand, such as facts and events) as well as procedural (those memories that are skills developed through repeated practice, such as playing the piano, keyboarding or wielding a tennis racquet).
How does the brain process information to turn it into memories? Memorization breaks down into three distinct stages:
- Stabilization, during which new data develops a resistance to interference from other information and “becomes” a memory.
- Consolidation, where memories are moved to structures in the brain where they become more permanent.
- Reconsolidation, whereby memories are strengthened, refined and modified for long-term storage as they are recalled and re-used.
Sleep plays a significant roll in the consolidation and re-consolidation stages of memory. Physiologically, slow-wave sleep (SWS) supports consolidation, while rapid eye movement (REM) sleep is more associated with reconsolidation processes.
From a purely practical standpoint, it boils down to this: a good memory requires a good night’s sleep. To keep one’s memory working, eight hours a night is a smart guideline. As for truly optimal memory function, the short daytime nap of sixty or ninety minutes—or even the five or ten minute cat nap—has been demonstrated to improve memory and recall.
For more reading, see:
- The memory function of sleep. Diekelmann and Born.
- Memory Consolidation and reconsolidation: what is the role of sleep? (PDF) Stickgold and Walker.