Sixteen subjects were instructed to discriminate whether the spatial locations of two visual stimuli presented in sequence were identical and event-related potentials (ERPs) were recorded from their scalps. The first and the second stimuli were presented in the same location in condition 1, but were in different locations in condition 2. ERP components of P100, N150, late positive component (LPC) and slow negative wave (SNW) were recorded in condition 1; in condition 2, N150 was enhanced and N270 was elicited before LPC. N150, N270 and SNW were all mainly distributed bilaterally over P3, P4, Pz, 01, 02,and Oz. N270 represents the brain activity for processing spatial discrepancy. There are several specialized brain areas involved in the generation of the N270. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.
基金：
The authors would like to thank Professor S.A. Hillyard for his valuable comments. This research was partly supported by Beijing Natural Science Foundation (7002021).
