In another study done in 2011 used stem cells to treat cerebral palsy. This study, however, was not as successful as the Parkinson's treatment. In this case stem cells were used to treat animal models who had been injured in a way that mimicked CP. This brings up a neuroethical issue of animal models used in science. Since most of their "diseases" are inflicted and do not occur naturally, they can not always be reliable examples of how a person with the actual disease would respond to treatment. The stem cells used did survive implantation, but did not show significant nerve regeneration. However, studies are ongoing in this area.