Highlight top level menu only

I have seen plenty of questions regarding highlighting of menus, but can find nothing to answer my question. If I click a menu item that is 2 layers down, all the items above it will be highlighted (all of the 1st layer categories and the top level menu as well). I really only want the top level menu to be highlighted.

I see that current_page_ancestor will make the top level item highlighted, but it also seems to highlight all the other items between the item clicked and the top level item. Essentially I just want the behaviour that WordPress has at the top of this page – only the top level item highlighted. Is this possible?