No doubt, you've had dreams that were culled directly from your real life. In fact, you've likely had one in the past week. Some of them may have even replayed events that happened that same day. Relationship and job stress can play out in your dreams on a nightly basis when you're in the midst of turmoil. Sometimes dreams mirror events as they happened in your waking life; sometimes there's a slight twist. Other times, they're filled with imagery and symbolism. There are no constants when it comes to dreams because they're highly personal and vary from person to person, which is why they're difficult to study or quantify with any certainty. It's also tough because we know so little about how the brain operates -- whether it's dreaming or figuring out a math problem.
Here's what we do know: Dreams definitely play out events from our waking lives. To understand how this happens, we should take a look at the way the brain processes memories. We all know that we have both long- and short-term memory, but there are subdivisions under those umbrellas that show us a little more about how our brain works. Under the long-term heading, we have episodic and declarative memory. Declarative deals with things you can state (or declare) that you know. Think "the sky is blue," "two plus two is four," and "my favorite food is steak." Episodic memories are there because of an experience you had -- "I'm afraid of seagulls because of the time I went to beach when I was 12, and one of them bit my finger."
Both of these types of memories are stored in the hippocampus region of the brain, and if you've damaged that area somehow, you won't be able to form new declarative or episodic memories. This is why permanent amnesiacs often can't remember things like the name of their dog or their home address. Because dreams are often culled from real life, some researchers believe that the brain is pulling from the recently learned declarative memories. But that's where amnesiacs come in to seemingly disprove that theory. If you aren't able to remember what you ate for lunch that day when you're awake, then you probably shouldn't be able to recall it in a dream either, right? Not necessarily, according to studies performed with amnesiacs. Learn more on the next page.
Implicit Memory and Dreams
In one Harvard University study performed in 2001, amnesiacs reported having dreamed about things that happened the previous day. Trouble was they didn't recognize the dream reflected their own experiences. In the study, amnesiacs played the block-stacking videogame Tetris for several hours each day. After they'd slept, they reported seeing large blocks falling and rotating, just like in Tetris, when falling asleep and in dreams. And because they were amnesiacs, they couldn't explain why they'd seen these blocks since they had no waking memory of playing the game. Does this mean that dreaming is a cure for amnesia? Not exactly, but it could mean that dreams aren't drawing from declarative memory at all, but from implicit memories.
Implicit memory, also known as non-declarative or unconscious memory, is just that -- memories that are not part of our waking consciousness but are there, nonetheless. Under the umbrella of implicit memory are procedural and semantic memories. Procedural memories include things like knowing how to ride a bicycle. You know how to do this, but you don't literally think "sit on the bike and put your feet on the pedals." You just hop on and ride. Semantic memories are more abstract, and live in the neocortex region of the brain. You saw an example of these abstract semantic memories in the dreams of the amnesiacs. While the participants could remember blocks falling, they didn't see themselves in a room sitting at a computer and actually playing the game. We also know that amnesiacs retain their implicit memories. That's why, after an injury, an amnesiac may not know his wife's name, but does remember how to flush a toilet.
This all leads to the theory that while we sleep, the brain goes over the millions of bits of information we take in each day in order to file everything away into the proper spaces. Dreams, some theorize, are what happen while this is going on. Work stress may play out in your dreams very clearly at times because your brain is giving it more weight than, say, the hot dog you ate for lunch. However, it's also possible for you to dream about the hot dog. Or maybe the hot dog is in your dream about your work stress. If it's true that the hippocampus is not responsible for dreams, and the answer lies in the neocortex and your implicit memories, then that also explains why your dreams can be very abstract at times.
At this stage, there really is no final answer as to how the brain transforms reality into dreams. But it's likely that it's tied to how we process our memories. As more studies of the brain, sleep and dreams are performed, perhaps our understanding of how our brain manages information will become clearer.
- "Dreams Tell Us That the Brain Is Hard At Work On Memory Functions." Beth Israel Deaconess Medical Center. 2010. http://www.bidmc.org/News/InResearch/2010/April/Stickgold.aspx
- "Episodic Memory." Vanderbilt University School of Engineering. 2010. http://eecs.vanderbilt.edu/cis/crl/episodicmemory.shtml
- "Memory is Plural." The Brainwaves Center. 2010.http://www.brainwaves.com/memoryIsPlural.html
- "The (Brain) Stuff Of Which Dreams Are Made." ScienceDaily. Sept. 13, 2004. http://www.sciencedaily.com/releases/2004/09/040913092356.htm
- "Types of Memory." PositScience.com. 2010.http://www.positscience.com/about-the-brain/brain-facts/types-of-memory
- Carey, Benedict. "A Dream Interpretation: Tuneups for the Brain." The New York Times. Nov. 9, 2009.http://www.nytimes.com/2009/11/10/health/10mind.html?_r=3
- Wren, Kathleen. "How the brain turns reality into dreams." Msnbc.com. Oct. 12, 2001. http://www.msnbc.msn.com/id/3077505/ns/technology_and_science-science/