Why does your brain dream while your sleeping?

First, what is a dream? A dream can include any of the images, thoughts and emotions that are experienced during sleep. Dreams can be extraordinarily vivid or very vague; filled with joyful emotions or frightening imagery; focused and understandable or unclear and confusing. Why do we dream? What purpose do dreams serve? While many theories have been given up, no single thought has emerged. Considering the huge amount of time reserchers and us spend in a dreaming state, the fact that researchers do not yet understand the purpose of dreams may seem baffling. However, it is important to consider that science is still unraveling the exact purpose and function of sleep itself.Some researchers suggest that dreams serve no real purpose, while others believe that dreaming is essential to mental, emotional and physical well-being. Ernest Hoffman, director of the Sleep Disorders Center at Newton Wellesley Hospital in Boston, Mass., suggests that "...a possible (though certainly not proven) function of a dream to be weaving new material into the memory system in a way that both reduces emotional arousal and is adaptive in helping us cope with further trauma or stressful events."Many other theories have been suggested to account for the occurrence and meaning of dreams.
The following are just of few of the proposed ideas:
•One theory suggests that dreams are the result of our brains trying to interpret external stimuli during sleep. For example, the sound of the radio may be incorporated into the content of a dream.

•Another theory uses a computer metaphor to account for dreams. According to this theory, dreams serve to 'clean up' clutter from the mind, much like clean-up operations in a computer, refreshing the mind to prepare for the next day.

•Yet another model proposes that dreams function as a form of psychotherapy. In this theory, the dreamer is able to make connections between different thoughts and emotions in a safe environment .

•A contemporary model of dreaming combines some elements of various theories. The activation of the brain creates loose connections between thoughts and ideas, which are then guided by the emotions of the dreamer.