What is the purpose of the vent that runs horizontally across the top of my windows and my sliding glass door?

I live in Seattle. The condo I moved into has has horizontal vents along the top of my windows and the sliding glass door. The vents are the thickness of the double pane, and have what appears to be a cylindrical chamber in them, which can be opened and closed. However, the odd part is that it appears the chamber cannot be opened in such a manner as to have air flow between outside and inside, the chamber opening is too small. It looks like it can only be either opened to the inside of the house or moved so the vent holes are still sealed within the window frame pointing towards the ceiling. I have never seen windows like this before, but they are frequent in the Seattle area. Thanks!