Elsevier

Biological Psychology

Volume 17, Issue 1, August 1983, Pages 41-58
Biological Psychology

Sequential effects on the ERP in discriminating two stimuli

https://doi.org/10.1016/0301-0511(83)90065-0Get rights and content

Abstract

Two auditory stimuli differing in pitch were presented in random order and equal probability with the constant inter-stimulus interval of 1 sec. The subject's task was to count one of these stimuli. The event-related brain potentials (ERPs) to each stimulus were averaged according to the immediately preceding stimulus sequence. It was found that when a few consecutive repetitions of one stimulus occurred, the ERP to the other stimulus immediately after those repetitions included features resembling those of the ERP to the infrequent stimulus usually observed in the so called ‘oddball paradigm’. These features included, among other things, the mismatch negativity usually regarded as a scalp reflection of the neuronal mismatch process with an existing neuronal model. The mismatch negativity was accompanied by an ‘N2b’, a sharper and later negativity. Interestingly. N2b only occurred when the not-to-be-counted stimulus succeeded (one or several) counted stimuli but not when the order was reversed. This suggests that N2b reflects template mismatch, the occurrence of a stimulus mismatching with the mental image of the target stimulus voluntarily held by the subject.

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    This research was supported by The Finnish Academy and The Emil Aaltonen Foundation (Tampere, Finland). The stimulating discussion with Drs W. Ritter and T.W. Picton is greatly appreciated. Dr S. Sutton's critical comments were particularly constructive. The authors thank Mrs Maija-Liisa Kettunen for typing the manuscript. Address requests for reprints to Mikko Sams, Department of Psychology, University of Helsinki, Ritarikatu 5, 00170 Helsinki 17. Finland.

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