🧠 What Happens in Your Brain While You Sleep During non-rapid eye movement (NREM) sleep — the deep, quiet part of the night — your brain is busy working. 💌 A courier service transfers short-term memories from the hippocampus to the cortex, turning them into long-term memories. 🧹 At the same time, your glymphatic system — your brain’s “vacuum cleaner” — activates to clear out waste from daily brain activity, glucose metabolism, and even negative emotions. Think of it as your brain’s nightly ho