Different processes are involved in human brain for shape and face comparisons

Fifteen subjects participated in a matching task of visual stimuli. Two seq uentially presented stimuli in a pair were the same shape (shape match), di fferent shapes (shape mismatch), same human face (face match) or different faces (face mismatch). All four kinds of stimulus pairs were of equal proba bility. The shape mismatch pairs elicited a negative event-related potentia l component N270 (Peak latency: 262.1 +/- 16.5 ms, P4) after the second sti mulus onset, while the face mismatch evoked N270 with longer peak latency ( 301.2 +/- 19.8 ms, P4) and N450. There exists a specific system for mismatc h processing of a complex stimulus (face) in the human brain. (C) 2001 Else vier Science Ireland Ltd. All rights reserved.