Hoverover Link to Change Associated Image

Hi,

I’ve searched quite a bit, old posts etc., but I haven’t had much luck…
I need to effect (change transparency, color, etc) an image when you hover over its associated link that’s shown elsewhere on the page. Ideally, I need a grid of post featured thumbnails that are made transparent when their post titles (listed below or in a sidebar) are hovered. And then vice versa. That is, the associated link is highlighted if the image is hovered.

This is exactly what I’m aiming for:
http://www.hariripontarini.com/projects/culture-spiritual