Purpose of touching tongue to roof of mouth during meditation While researching forms of meditation involving concentration specific to the Tibetan school of Buddhism, the meditation instruction tells one to touch their tongue to the roof of their mouth when meditating. 

Recently, I have been reading a book on Taoism and energy flow, which also instructs the same thing yet for the purpose of completing an energy pathway.

My question:

What is the purpose of touching the tongue to the roof of the mouth when meditating (in concentrated meditation in Tibetan Buddhism)?



I would also welcome some answers/comments about other schools of Buddhism related to this.
As it was explained to me, the purpose is rather mundane. During some kinds of meditation, esp. when one penetrates lower chakras, there is lots of saliva generated, swallowing which can be quite a distraction and interfere with abdominal breathing. Raising the tongue makes most of saliva flow back into the throat instead of filling the mouth.

P.S. in a commentary to ancient Chan text "Lung Chung" (The Brief Precepts) it says that pressing the tongue to the roof of the mouth eliminates the objects of discursive (speech-type) thought.