because in other diseases that were discussed like schitzophrenia or depression, you can't point to a single gene that can do it for you. so it's lots of little genes that seem to be responsible. and to figure out how those kinds of diseases work is much more difficult. so even though the progress at the moment seems to be very slow, our understanding of it has been really amazingly rapid. >> we were able to make animal models in fact of the disease by taking these very genes and mutations and introducing them into a mouse. before that though there really was no small animal model of disease and so it made it extremely difficult for scientists. >> rose: explain what happened when you introduced them into the mouse. >> as the mouse ages, there are changes in the brain that lead to aggregation of the same protein in the brain as you see in humans. and in some of the mouse models, there's some suggestion they also be some changes in memory in these animals. it's not a perfect representation of the disease. >> the representation is that the mouse only lives to be two years old while alzhe