The study, by Columbia and University of Colorado researchers, showed that stem cell surgery � an experimental type of treatment widely thought to hold great promise for treating many brain disorders � doesn't have immediate applications. However, experts say stem cell research should continue.

"It's not the answer to Parkinson's Disease, that's one thing," said Stanley Fahn, professor of neurology at Columbia's College of Physicians and Surgeons. But, he added, the study did provide "proof of principle" that the theories underlying the treatment are fundamentally sound.