The nature of the late positive complex within the olfactory event-related potential (OERP)

Authors


  • The study was supported by a grant from the Volkswagen Stiftung.

  • We thank Prof. Dr. F. Rosler for his helpful suggestions on a preliminary version of the manuscript and B. Gottsmann and K. Rogalski for their technical assistance.

Address reprint requests to: Dr. B. M. Pause, Institute of Psychology, Olshausenstr, 62, University of Kiel, 24098 Kiel, Germany

Abstract

The olfactory event-related potential (OERP) has been described as being dependent on exogenous stimulus features, but no effect has been made to examine possible endogenous determinants. We wanted to separate exogenous and endogenous components of the OERP by using an olfactory oddball paradigm. A high concentration of citral was used as the target stimulus, and a low concentration was used as the standard stimulus. Odors were presented within a constantly flowing air stream. We found that the early components of the OERP (N1, P2) are modulated by the stimulus concentration, whereas the late positive components (P3-1, P3-2) vary depending on the subjective stimulus significance and stimulus probability. It is concluded that the positive component of the OERP, which has been formerly explained by chemical and physical stimulus features, is actually determined by endogenous processes.

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