27" LED Cinema Display, no brightness control

I have a 27" LED Cinema Display that has the Mini DisplayPort cable and I am plugging into a MacbookPro 15" with a thunderbolt port. When I go into System Preferences there is no brightness control or ability to turn off automatic adjustment for the LED display, just the computer. I have the usb port plugged in as well. I have seen previous updates to fix this for earlier versions (10.6) but that didn't work on my OS X 10.8.2. Is there anything to remedy this? The automatic adjustment of brightness is very distracting and I would like to have control of the brightness of my monitor.