where to add / adjust notification option in userCP

[feras]

I'm trying to find where in the DB the information for email notifications (that can be set in the userCP) is stored.

I would like to add an additional check box there, for notifications on a custom feature on the site. I know where that tidbit is in the style, but can't seem to find where it is in the DB, and hopefully add a field to that table and easily have the data available to me in my style modification.

any help is appreciated
thanks