Is there a part of the human brain responsible for triggering imagination, fantasy and coming up with unusual stories? I'm trying to understand if there's a specific process or part of the human brain which, when activated, causes the person to daydream, engage in fantasy or come up with ideas that are far from common reality? In other words, what is the trigger that initiates imagination process?
Examples

Looking at the clouds and guessing their shapes - there's no animals, unicorns or majestic castles in the sky - there are clouds, but the brain still comes up with unusual explanations.
Thinking about &quot;What would I do if I was teleported back in time&quot; or &quot;what if I had super powers&quot;. I'm interested in what causes this slip into daydreaming.
When a person in love is fantasizing about a romantic partner and attributes all kinds of traits to them. Once again, some kind of trigger modifies thinking pattern.

Question
The phenomenon I'm talking about might be related to when people suddenly start to think about all kinds of stuff, real or imaginary upon going to bed (which prevents them from falling asleep).
It seems to me that all of these share a common theme, and I'm trying to learn if they are bound by some physical process or part of the brain.
This question is related to this question about factors that trigger creative thought in humans
There is no known specific process or part of the human brain which, when activated, causes the person to daydream, engage in fantasy or come up with ideas that are far from common reality. Instead, imagination is a broad-based activity which involves and overlaps with many brain regions and cognitive processes.

The cognitive neuroscientific basis of imagination is believed to comprise a core network of brain regions, which seems to utilize parts of a vast and broad-based set of other regions for different purposes. There are too many of these to list, but the main activity seems to revolve around the frontal lobes, parietal lobes and the hippocampus. Interestingly, and consistent with the idea of memory as a generative process, the brain regions involved in imaginary events appear to be highly related to the regions involved in episodic memory retrieval for real events.

Hassabis, Kumaran and Maguire (2007) report relevant fMRI evidence on imaginary scene construction:


  Our results show that when subjects construct new fictitious scenes an extended brain network involving the hippocampus, parahippocampal gyrus, retrosplenial cortices, posterior parietal cortices, and ventromedial prefrontal cortex is active. Critically, we show using a conjunction analysis that this network is not specific to the construction of new fictitious experiences, but is also engaged when subjects remember both previously imagined experiences as well as their own real personal experiences. The implication is, therefore, that this distributed network supports cognitive operations engaged in common during the three main conditions in our experiment, most likely the (re)construction, maintenance and visualization of complex scenes.


These are associations, however. The results should not be taken to support the idea that there exists any process/brain region or set of brain regions which, if stimulated, will cause a person to daydream or engage in fantasy, only that these regions are active when people do so. This is always true for neuroimaging studies, but this is doubly true when the results involve a dozen or more areas.

References


Hassabis, D., Kumaran, D., &amp; Maguire, E. A. (2007). Using imagination to understand the neural basis of episodic memory. The Journal of neuroscience, 27(52), 14365-14374.