(CBS)

Yesterday on the "Evening News," anchor Katie Couricinterviewed actor and activist Michael J. Fox. Fox, who suffers from Parkinson's disease, has been in the spotlight over an ad in which he lauds Missouri Democratic Senate candidate Claire McCaskill and criticizes McCaskill opponent Jim Talent over their positions on stem cell research. Radio talk show host Rush Limbaugh has suggested that Fox, whose body was rocking from side to side during the ad, was "either off his medication or acting" when he filmed the spot.

After her interview with Fox, Couric said the following: "By the way, in the spirit of full disclosure, I think it's important to mention that my dad has Parkinson's disease. He told me today it's okay to tell you that. And in the past, I've made contributions for Parkinson's research through Michael J. Fox's foundation.”

I asked Couric about the disclosure.

"The reason I donated to his foundation is because of my father. It was a combination of my admiration for Michael and my personal experience with my dad," she said. Couric said she had introduced people at events for Fox's foundation in the past, and she didn't want people to suggest she was trying to hide her connection to him.

Did her personal experience with Parkinson's influence the way that she conducted the interview or framed the story?

"I don't feel like it really reflected or influenced my approach," said Couric.

"I think I probably have even more sympathy for his situation, and I think I understand the science better than some other people," she said. "But I challenged him on questions people who support stem cell research would not necessarily want asked" – such as ethical "slippery slope" questions inherent in embryonic stem cell research and the notion that such research could conceivably be done exclusively in the private sector.

Couric also said she "wanted to be responsible to Rush Limbaugh's true feelings." She said many news outlets only excerpted the most incendiary clip of Limbaugh's comments, and that it was important to provide a full accounting of his views. During the interview with Fox, Couric read a comment that Limbaugh made directly to the "Evening News."