1. Laboratory of Neurophysiology; National Institute of Neurological Disorders and Stroke. National Institutes of Health; Bethesda MD 20892 U.S.A.
2. International Institute of Genetics and Biophysics, C.N.R.; Naples Italy
3. Laboratory of Clinical Science; National Institute of Neurological Disorders and Stroke. National Institutes of Health; Bethesda MD 20892 U.S.A.