Detect button on a ground line (reverse eng)
It sounds like you might have a PCB with debounced switches on them. One such circuit for debouncing switches looks like this:



That circuit and more about switch debouncing can be found here.

A debouncer basically masks the problem of switch "bounce" which is what happens when the contacts get close and the circuit is quickly closed and opened in rapid succession until a firm connection is obtained. Its a natural problem  mechanical switches.

If that's not quite right, maybe you could help us help you better by posting a photo of the board in question.