Brain waves following remembered faces index conscious recollection

At a glance, one can often determine whether a face belongs to a known indi vidual. To investigate brain mechanisms underlying this memory feat, we rec orded EEG signals time-locked to face presentations. In the study phase, 40 unknown faces were presented, 20 of which were accompanied by a voice simu lating that person speaking. Instructions were to remember the faces with s poken biographical information (R-faces) and to forget the others (F-faces) . In the test phase, famous and non-famous faces were presented in a visual ly degraded manner. Subjects made two-choice fame judgments and priming was observed in the form of faster and more accurate responses for old than fo r new non-famous faces. Priming did not differ between R-faces and F-faces. In a second experiment, faces were not degraded at test and behavioral res ponses were made only when faces were presented twice in immediate successi on. Brain potentials elicited 300 to 900 ms after stimulus onset from front al and parieto-occipital scalp regions were larger for R-faces than for F-f aces. Recognition tested later was more accurate for R-faces than for F-fac es. Because the study-phase manipulation influenced recognition but not pri ming, we conclude that this procedure succeeded in isolating neural correla tes of recollective processing from more automatic uses of face memory as i ndexed by priming. (C) 1999 Elsevier Science B.V. All rights reserved.