Received January 20, 1995; final revision received April 5, 1995; accepted April 25, 1995.From the Departments of Neurology and Neurological Surgery and of Cell Biology and Physiology (C.M.R.), Washington University School of Medicine, St Louis, Mo.Presented in preliminary form at the 24th Annual Meeting of the Society for Neuroscience, Miami Beach, Fla, November 13-18, 1994.Correspondence to Thomas A. Woolsey, MD, Department of Neurological Surgery, Campus Box 8057, Washington University School of Medicine, 660 S Euclid Ave, St Louis, MO 63110.