The dipole location shift within the auditory evoked neuromagnetic field components N100m and mismatch negativity (MMNm)

Objective: To investigate whether within the latency range of the neuromagnetic mismatch negativity (MMNm) a similar dipole shift can be observed as found in previous studies for the auditory evoked field component N100m. Methods: For this purpose selected neuromagnetic data of 29 subjects were analysed in a time window of 15 ms before and 15 ms beyond the peak maximum of both components. In our oddball paradigm, we applied frequency, duration and intensity deviants within one block. The time course of dipole location was analysed by means of a repeated measure analysis of variance (ANOVA). Results: As expected, N100m dipoles shifted significantly from superior to inferior and from posterior to anterior within their latency range. In analogy, the MMNm dipoles of duration and intensity deviants also exhibited a significant shift from posterior to anterior within their latency range. However, the MMNm dipoles of all 3 deviants did not shift significantly from superior to inferior. Concerning this direction, the ANOVA revealed a significant TIME*COMPONENT interaction between the N100m and the MMNm of duration and intensity deviants. Conclusions: The finding of a different time course of N100m and MMNm dipoles does not support the assumption that the MMN represents an amplitude- and latency-modulated auditory N100 response. (C) 2004 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.