David, the only way I found so far is to go directly to the git repo for this. Using the SHA or ref from the patch-set you can lookup "author" in the git repo.
Read more here:
http://stackoverflow.com/questions/16985686/how-to-get-patchset-author-out-of-gerrit
Either you have to ssh to Gerrit and fire the git cmd, or have a local replica of the git repos to work on.
Also note that "uploader" and "committer" is not the same. And the proof is: The "uploader" include the "username" parameter which is Gerrit specific.
So actually you get neither "author" nor "committer" when using "gerrit query". But you can get both from browsing the git repo.
/Jonas