I had a familiar dream recently. It was near the end of the semester in my dream and I had not attended many of my calculus classes. I knew I would fail and I was desperately searching for a way out of this mess. As I woke from my dream, I realized that I had nothing to fear from calculus. I had graduated in spite of it and would never have to pass calculus again. But it got me to thinking, "What triggered that dream?" My friend confessed to having similar dreams, along with the ever popular "locked outside naked" dream and the ubiquitous "running from something horrible" dream.
I came to the conclusion that a basic emotion was at the root of it, that fear or anxiety perhaps triggered by any number of possible sources, real or imagined, was being expressed in that dream. It was my sleeping brain's way of making sense out of the basic emotion of fear that was firing while I slept.
Survival emotions, such as fear, anger, or shame, prepare our bodies for dangerous situations, prepare us to run or fight or surrender, depending on what seems best. They also stimulate the creative problem solving cognitive centers of the brain to figure out what we know about the source of the danger and what we can do to defend against it. When we are asleep, and something triggers fear - an erratic heartbeat perhaps or a little difficulty breathing - or maybe leftovers from a stressful day - fear directs our brain to search for the source of the danger based on what scary things we have experienced in our life and stored in our memories. Then it is as if Stephen King is writing the script and Alfred Hitchcock is directing the movie of your own personal fear dream, using the material that works best with the emotion that you are experiencing.
The brain evolved to protect us in situations much more dangerous than the one most of us live in today. If you were afraid, there could be a good reason, so you would be highly motivated for getting ready to run and vividly remembering all you knew about dangerous stuff. As you remembered it, you might visualize it, and the movie of the lion in the tall grass would be played out in the theater of your mind.
It occurred to me that all of our thinking is a response to two kinds of data, one source of data is the outside world that we can observe and monitor, but the other source is the emotion we are experiencing. The emotions determine how we interpret the data from the outside world. If I am walking down the street wide awake, but feeling vaguely anxious, I will probably scan the oncoming pedestrians for suspicious characters, or I might imagine that garbage truck jumping the curb and squashing me like a bug. If I am hungry, I am more likely to notice the proximity of restaurants or candy at the checkout.