According to the activation-synthesis hypothesis of dreaming, random electrical activity in the is interpreted by the to create a story line.

The answer is Brainstem and Cerebral Cortex.  In which according to the activation-synthesis hypothesis of dreaming, random electrical activity in the brainstem is interpreted by the cerebral cortex to create a storyline. The activation-synthesis theory is a neurobiological explanation of the theorist of why dreaming happens. The theory was proposed in 1977 in which signifying that dreaming fallouts from the endeavor of the brain to make sense of neural activity that takes place throughout sleeping.