1. From the Department of Physiology and Biophysics (A.P., Y.Q., N.H., J.A.H.), the Department of Medicine (F.L.R.), Section of Cardiology, the Department of Radiology (F.L.R.), the Department of Anatomy and Neurobiology (K.J.H.), and the Department of Neurology (J.V.), Boston University School of Medicine, Boston, Mass; and the Department of Biomedical Engineering (J.A.H.), Boston University, Boston, Mass.