About this episode
The final installment of this series focuses on what happens inside your brain during deep, non-REM sleep that allows you to fixate new memories. There are at least two mechanisms at work here. One is a process of shifting information from short to long-term memory. Each night when you go into deep non REM sleep, those long range brainwaves of deep sleep are going to be moving packets of information, from that short term, vulnerable, USB stick-like memory reservoir (the hippocampus) to the safer long term storage site (the cortex). When we wake up each morning, we've now cleared out that USB memory stick, and we've refreshed and restored our ability to start learning new memories. This process repeats, filling up the USB stick with new information during the day, and then at night, transferring those memories over to the long term storage site in the cortex. The second memory mechanism, memory replay, is very different. Back in the 1990s, scientists recording the activity of individual brain cells in the memory centers of rats running around a maze discovered that different brain cells coded different parts of the maze. More remarkable was the discovery that the sleeping brain would replay these new memory sequences during deep, non-REM sleep much faster than standard waking speeds. This meant the memory trace was being replayed many times, and the brain was repeatedly etching it more permanently into the brain. There is at least one other time during sleep when we see memory replay—REM sleep, the stage when we dream. But here, memories are replayed at much slower speeds, sometimes just half the speed of waking experience. Because of this temporal distortion - where time within the dream is slowed down and expanded - you will feel as though you have been dreaming for far longer than you actually have. The movie Inception, in fact, draws some inspiration from this concept - almost as though the director and the writer of the movie Chris Nolan had a little bit of idea help from a sleep scientist! Please note that Matt is not a medical doctor, and none of the content in this podcast should be considered medical advice in any way, shape, or form, nor prescriptive in any way. Today's podcast is supported by biochemical electrolyte drink company LMNT, and they are very kindly offering eight free sample packs when you purchase any one of their orders at drinklmnt.com/mattwalker . LMNT is an electrolyte sports drink that I can get behind - it's created from the basis of science, and it has no sugar, no coloring, and no artificial ingredients – all qualities that are so important to maintaining your blood biochemical balance. If you want to give LMNT a try, just head on over to drinklmnt.com/mattwalker and get your eight free samples with your first purchase. Another sponsor today is MasterClass - the online streaming platform where anyone can learn from the world's best about a variety of topics such as cooking, art, science, and, of course, technology. When you sign up, you get access to all of the classes taught by such masters as Martin Scorsese, Venus Williams, and Neil deGrasse Tyson, to name a few of Matt’s favorites. You may even find a masterclass from a familiar sleep scientist! This year, Masterclass is offering a special gift for the holidays - buy one annual Masterclass membership and get another one totally free! So if you're curious and have a thirst for learning, head on over to masterclass.com/mattwalker now. And, as always, if you have thoughts or feedback you’d like to share, please reach out to Matt on Instagram .