All participants were right-handed (Oldfield, 1971; laterality quotient, controls vs. patients, 73.6 ± 29.2 vs. 84.0 ± 18.3). Patients tended to have less education than control participants, but this difference was of only marginal significance (14.2 ± 2.7 vs. 15.5 ± 1.7 years), F(1,63) = 3.77, p =.06. Participants were instructed to refrain from smoking on the day of test. OERP recording sessions were scheduled between 9 a.m. and 5 p.m. and lasted about 1.5 h. Time of testing did not differ between groups, F(1,63) < 1.0, n.s., thereby controlling for putative circadian influences on OERP amplitudes (Nordin, Lötsch, Murphy, Hummel, & Kobal, 2003). The experimental protocol had been approved by the institutional review board and was undertaken with the understanding and written consent of each participant.
