What triggers creative thought in humans?
This is a part answer to your question.

The three-factor anatomical model of human idea generation and creative drive presented in "frontotemporal and dopaminergic control of idea generation and creative drive" (Flaherty, 2005) focus on interactions in and between the temporal lobes, frontal lobes, and the limbic system. 

Increase in the quantity of idea generation, at times at the expense of quality is associated with changes in the temporal lobe.  Conversely, frontal lobe deficits may decrease the quantity of ideas generated, largely due to judgements of an idea's worth.  The authors assert that interaction between the two mainly affects verbal and some non-verbal creativity
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Further,


  Mesolimbic dopamine influences novelty seeking and creative drive. Dopamine agonists and
  antagonists have opposite effects on goal-directed behavior and hallucinations.


The authors emphasise that creative drive is not the same as skill, and that the 3-factor model is an alternative to the left and right brain hemisphere skills based model.