1. CP Zwetsloot, JFV Caekebeke, Department of Clinical Neurophysiology; JC Jansen, MD Ferrari, Department of Neurology; all at University Hospital, PO Box 9600, 2300 RC Leiden, The Netherlands; J Odink, Department of Experimental Biology, TNO Division of Nutrition and Food Research, PO Box 360, 3700 AJ Zeist, The Netherlands;