Monitor dims when using laptop mouse pad?

Now this is an odd problem. Never heard of it, nor can I find any instance of it on Google.

When I use my mouse pad on my laptop (the one you use you drag your fingers on), my screen goes very dark and sometimes flashes back to being bright. When I plug in a new mouse into a USB drive and use it, everything's fine though. So I can adapt to this, but I'm just wondering if there's any way to fix it or prevent any further problems. Any help would be greatly appreciated, thanks!