Background task in Scala

I have a cache I want to periodically check and prune. In Java, I'd do the following:

new Thread(new Runnable() {
  void run() {
    while (true) { 
      Thread.sleep(1000);
      // clear the cache's old entries
    }
  }
}).start();

Sure, I'd have some issues with thread-safe types to use as the cache, but putting that aside, my question is simple. What's the Scala way of running a recurring background task -- something you don't want running in the application's main thread?

I've used actors a bit and I guess my problem in this scenario is that I don't have anything to generate a message that it's time to clear the cache. Or rather, the only way I can imagine to generate those messages is to create a thread to do it...

EDIT: I need people to vote on answers -- they all look good to me