Im sure this question has been asked before but i dont really have to time to go scouring over the old threads looking for it.

The mudvayne bassist Ryan Martinie.

Ive noticed in a few of their live performances that Ryan, instead of just plucking the strings like normal he kinda hits downwards on them. can someone tell me what this technique is called and how to do it? ive heard it makes your right hand a little faster. and also gives that thumping sound.

Does he use his thumb as a pick and stuff? I forget what that's called...but I don't really like Mudvayne anyway....
It's a flamenco technique that Geddy Lee also uses. It's simply brishing your fingers back over the strings and hitting it with your fingernail. It's just about the fingerstyle equivalent of alternate picking.