Sleep is the only opportunity for the brain to get organized -- truly organized, not just piling files on the desk and promising to get back to them later. When we don't sleep, our brains don't have an opportunity to, as some researchers like to call it, take out the trash. While it sounds funny, there's science behind it -- we know that sleep deprivation really seems to speed up the development and the progress of neurodegenerative diseases, including two biggies: Alzheimer's disease and Parkinson's disease. And researchers suspect it's because without sleep, the body's glymphatic system (the central nervous system's cleaning service) isn't able to trash the waste that builds up throughout the day. In this case, the trash is cerebrospinal fluid (CSF) thick with accumulated proteins and toxins. We also know that a lack of sleep causes permanent brain cell loss, likely due to how a sleep-deprived body is unable to properly manage cell growth and repair. If you don't clean up from time to time -- or nightly, in this case -- you're signing up for memory problems and an overall cognitive decline.
While you're sleeping, your brain is also busy doing some high-level cognitive activities, including reviewing and sorting information from the day, and flagging important and novel things that should be committed to memory. When we learn and store information in our memory, that information is moved from the hippocampus (which is known as the memory-creating region of the brain) to the prefrontal cortex (PFC), specifically the neocortex region, which is where we form and store long-term memories. This happens every night, while we sleep. Without deep sleep a few problems may arise: First, we simply can't recall -- literally. And second, a phenomenon known as false memories may also happen to people who sleep five or fewer hours every night. Fatigue impacts not only memory recall, but also how you process information in general. You can't properly access memories, and you also can't properly encode information when you learn it. That makes what you think you know unreliable, or, at the very worst, incorrect.