Mouse Move Performance

I am trying to improve the speed of my viewport (containing around 100 models) and I cannot figure out why the processor spikes when I am moving the mouse over the viewport.
https://www.youtube.com/watch?v=QysWHudOvdQ

I would like to be able to add more 3D models to my viewport and I am looking for a way of reducing the CPU load. Is there some functionality which can be "sacrificed" to get better performance?

Thanks,
Blanka

WPF might be doing hit-testing while you move the mouse. There is some way to disable this, and then only do hist testing when you need to, or on a timer. See: http://blogs.msdn.com/b/wpf3d/archive/2009/05/18/3d-hit-testing.aspx

-Govert