A common sleep recommendation is to limit naps! Wait, what?
Anyone who has struggled to get children to nap should be laughing so hard now they might be crying. As a parent of two young boys, I cherish times when they both settle down for an afternoon nap. Certainly, children should be getting more sleep than adults, but how tempted am I to nap with them? Mayo Clinic.org (2) explains that adults who nap should pay attention to the length of their nap. They suggest that going past 90 minutes in a nap is a deal breaker. After 90 minutes you typically progress into deeper sleep. Spending too much time or not enough in deep sleep stages can cause you to feel terrible after you wake.
I have been teaching my students about the role of sleep in forming memory for a while now. Psychologists Georg Muller and Alfons Pilzecker were among the first to suggest that what we learn changes overtime, and sleep can account for some of this change by improving long-term memory (3). They found that participants learning short sets of “non-sense” syllables (e.g., FOV) would recall syllables randomly, over time, even when these syllables were no longer being tested. They called the ability to remember without intention, “perseveration.” Consider not being able to stop thinking about an embarrassing event, long after you were embarrassed; this is perseveration. Muller and Pilzecker called the process of consistently remembering consolidation. This word makes me think of taking all the leftovers in my fridge and planning to eat what is still good and throw out what is too far gone each week. Consolidation is an important process to remembering.
When we make new memories, the hippocampus is heavily relied upon. Over time, memories begin to rely predominately on the cortex and in turn, less on the hippocampus. It is not that the knowledge “moves” from one place to the other. It is that as time passes, we tend to use and connect long-term memory with other memories (4). This image from research by Gordon and Diekelmann depicts how information at learning relies on activation of the hippocampus, but, after sleep and retrieval, activation shifts to the cortex.