
It is not known at this point however where dreams physically start in the brain. In fact, it is not even known if there is only one starting point of dreams in the brain, or if several parts of the brain play a role in dream formation. Though dreams to have a biological basis, there is no conclusive evidence that indicates where that basis is, other than REM sleep.
The general purpose of dreams is to give the body a chance to rebalance and recycle itself throughout the sleep period. Dreaming allows us to balance out the experiences we lived during the day, week, or recent past. Studies do indicate that interrupting the dream period or REM cycle will lead to extreme disruption for humans. We will act irritable, anxious, angry, and some studies even report psychotic like experiences as a result of dream sleep.
So, while we know that dream sleep restores and maintains our mental balance, it is not unwise to think that the emotional centers of the brain play a major role in the causes of dream formation. Unfortunately, science has not been able to come up with the precise cause of dreams, but we do know that in all mammals, it is biologically based.