Can a lender call a loan due to negative equity?

[Tyler Richard]

I would like to know if a lender can foreclose on a property or call a loan or require an influx of cash if the loan for the property is upside down? I've seen several articles online about negative equity, but if the borrower continues to make payments, can the lender request the borrow to bring the equity and loan amount equal again? Any input on this subject would be great.