[1] NINCDS, COGNIT NEUROSCI SECT, NIH, BETHESDA, MD 20892 USA
[2] NINCDS, CLIN NEUROGENET UNIT, NIH, BETHESDA, MD 20892 USA
[3] NINCDS, MED NEUROL BRANCH, HUMAN MOTOR CONTROL SECT, NIH, BETHESDA, MD 20892 USA
[4] NINCDS, NIH, NEUROEPIDEMIOL BRANCH, BETHESDA, MD 20892 USA