PHOENIX (AP) — Muhammad Ali and his family never seriously thought of donating his brain for research, according to the doctor who treated the boxing great.

"Not really," was Dr. Abe Lieberman's answer when he was asked Monday if submitting the brain for research was considered.

Lieberman said he didn't think boxing contributed to Ali contracting Parkinson's disease but he couldn't be "a hundred percent" certain.

The doctor spoke at a news conference at the Muhammad Ali Parkinson Center at the Barrow Neurological Institute in Phoenix.

Lieberman was among those who diagnosed Ali in 1984.

The doctor said he believes Ali had the disease earlier, when he fought Larry Holmes in 1980.