Even among scientists who disagree about the dream process, no one thinks that dreams have only one purpose. Since dreams can occur at different times during the sleep cycle, they have different functions. Let's look at a few that have been proposed.
Some researchers do believe that dreams help the brain organize and manage the tremendous amount of day-to-day input humans face. Evidence of this in found in research on infant sleep. Most dreams occur during REM (rapid eye movement) sleep, which is normally characterized by brain activity very similar to waking and significant body paralysis (still allowing for twitches and eye activity). This occurs during roughly 20 percent of adults' sleep sessions, but infants are in REM sleep during half of their slumber hours. Infants need to categorize and understand an entirely new world, but they spend a good deal of their time asleep. In order to be efficient, it's likely that their active brains are multitasking, using sleep to help deepen the neuron pathways for new information. Studies with infant and adult rats indicate they share the same type of neuron firing during sleep. Researchers concluded that if the purposes of sleep were different for infants and adults, then their brain activity would not be comparable [source: Karlsson, et al]. Therefore, it's a safe bet that a good deal of dream time is spent organizing data we've absorbed.
What else could be happening? Some therapists think that a good deal of a person's dreaming is the unconscious knocking on the door, trying to get out and express itself. This began with Freud, who believed the unconscious focused on aggression and sex. Modern therapists adopt a wider view of the unconscious, believing it contains information about many topics our brain hasn't (or won't) process.
There are brain researchers who believe that many of our dreams are simply random neuronal firing. Since a dreaming brain is obviously very active but not technically conscious, the brain is essentially producing dreams to keep itself busy. This could account for the seemingly disjointed and weird aspects of some dreams.
Much information has been collected about dream states using technology such as PET, EEG, EOG and EMG, as well as observations of sleepers and self-reports of dreams. The brain, however, is not yet wide open for exploration and still holds many secrets, including the details of dreaming.
If we use eight hours of sleep as a benchmark, we spend about one-third of our lives asleep. That's a lot of time spent on the other side of wakefulness. (Fortunately, for most of us, it's at least an enjoyable respite!) We spend a lot of that time dreaming, too. But what is the brain trying to accomplish by dreaming? Is it just a meaningless, slumber-time collection of incomprehensible movie sequences (some researchers think dreams don't really serve any function at all, arguing that they are just a pointless byproduct of the brain firing while we slumber)? Or does our dreaming have a purpose? We know that the rear portion of our brain is very active during R.E.M. sleep, which is when most dreaming occurs, so is there a point to it?
What if our dreams are the brain's way of cleaning house? One theory posits that dreams are the result of the brain sorting through everything it clings to while it and we are awake. The idea is that everything from minor sensory details to far more complex issues is categorized and prioritized for memory storage, with the help of dreams, as if dreams are the brain's vivid "Post-It" notes, reminding our gray matter to sweep up after the day's work. This theory is backed up by the fact that we dream more when we're actively learning something new, like a foreign language.
Whatever the case may be, whether or not we dream in order to organize sensory input, one thing is for sure: We need our sleep. Being deprived of sleep can have serious consequences, especially if the lack of good "Zs" is chronic. When we're not sleeping well, our alertness tapers off, we can't think clearly enough and our memory function is impaired. Furthermore, quality of life goes out the window for a "sleepless" person, who also sees in his or her life an increased risk of injury either on the job or out in the world [source: WebMD]. There are probably as many theories for why we dream as there are dreamers themselves. Instead of worrying why we dream and what the nightly slide show means, perhaps it's best if we just focus on getting a good night's sleep.
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