Dreams are so strange and carry so much significance to us that we often feel the need to tell people about our nocturnal adventures, sometimes at tedious length. But if you understand what goes on inside the brain as dreams take their course, they start to make a lot more sense. And dreams are much more important than you might think. Here are some common questions answered about the nighttime hallucinations we call dreams. 1. Why are dreams so weird There's a good reason dreams are so skittish and peculiar. Memories of life events – "episodic memories" – are stored in a part of the brain called the hippocampus, and in rapid eye movement (REM), sleep signals coming out of the hippocampus are shut off. That means we can't access specific memories of things that happened in the past while we dream. But we can still access general memories about people and places, which form the backbone of our dreams. At the same time, activity in brain regions involved in emotional processes are cranked up, forming an overly emotional narrative that stitches these memories together. As an example, I dreamed recently that a flood had surrounded the house in which I grew up; I needed to try to fly out of the window to escape but I'd forgotten how to fly. The overwhelming feeling was emotion – fear and anxiety about the rising water levels and my inability to fly. Another part of the brain, the dorsolateral prefrontal cortex, which controls our powers of both logical reasoning and decision-making, is also shut down. I don't stop to question why the floodwater is rising so fast, or why I'm back in my childhood home, or even why flying to safety is an option. This difference in brain activity compared with when we are awake helps explain why we feel like we have such scant control over our dreams – we are observers, along for the ride – and why when weird things happen, we don't raise an eyebrow until we wake up. In my dreams, I often end up breathing underwater, as if it were completely natural. 2. Do we only dream in REM sleep? The study of dreams – which for centuries was more of an exercise in imaginative explanation than anything approaching science – started properly in 1953, when Eugene Aserinsky and Nathaniel Kleitman at the University of Chicago hooked volunteers up to EEGs that detect electrical activity in the brain and woke them during different sleep stages. Read More: Science Alert
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