Alzheimer's disease isn't what it used to be. After 30 years of having doctors diagnose the disease by symptoms alone, researchers and advocacy groups are calling for new diagnostic criteria that recognize changes in the brain as well as changes in behavior.The goal is to eventually allow doctors to diagnose "preclinical" Alzheimer's in patients who do not have problems with memory or thinking, but who do have an abnormal brain scan or some other sign that the disease may be developing.