<qa>  What is the name of the study that the investigators propose to analyze tissue samples from different nervousIn this project the investigators propose to analyze tissue samples from different nervous system regions obtained during neurosurgical procedures in order investigate the presence of neural stem cells in different cerebral areas. The investigators will also evaluate techniques for neural stem cell cryopreservation, for possible future therapeutic uses. Patients with degenerative neurological disorders like Parkinsons disease undergoing neurosurgical procedures meeting our selection criteria will be candidate for this study. 