nancy banini. she subjects the genetic basis of disease by performing experiments on fruit flies.he is a professor at the university of pennsylvania and a howard hughes medical investigator. joining me from atlanta is melan delong, an expert on parkinson's disease and a pioneer in the growing field of deep-brain stimulation, a professor of neurology at emory university school of medicine. our co-host is dr. eric kandel, a nobel laureate, a professor at columbia university and a howard hughes medical investigator. i am pleased once again to have him here to help me understand all about the brain. welcome back. >> thank you. you're doing very well understanding the brain. >> charlie: what a journey it is. tell me about today -- the disordered brain. >> last time, we discuss -- >> last time, we discussed psychiatric disorders. today we're going to discuss neurological disorders. disorders of the brain. one of the things youwant to explore is how are they different from one another. there are two fundamental differences. one in the nature of the symptoms. and two, in anatomical locati