Aspartame safety and a study done by Dr. John Olney

http://www.fda.gov/ohrms/dockets/dailys/02/aug02/080102/98f-0052-her0001-vol5.txt

This seems to be a letter to the FDA about aspartame. It mentions a study done by Dr. John Olney in which he says more studies need to be done. One of my friends posted this youtube link which mentions the study.

Any thoughts? What does askscience think? Was the study discredited at any time (I can't seem to find any more concrete/scientific info on it).