Separate time behaviors of the temporal and frontal mismatch negativity sources

It has been proposed that mismatch negativity (MMN) is generated by tempora l and frontal lobe sources, the former being associated with change detecti on and the latter with involuntary switching of attention to sound change. If this switching of attention is triggered by the temporal cortex change-d etection mechanism, one would expect that the frontal component of MMN is a ctivated later than the temporal one. This was studied by using 64-channel electroencephalography (EEG) and 122-channel magnetoencephalography (MEG) w ith realistically shaped head models to determine the source current distri bution in different lobes as a function of time. Minimum-norm estimation (M NE) was performed, constraining the solution to the reconstructed cortical sheet. The results support the hypothesis that the frontal MMN generator is activated later than the auditory cortex generator. (C) 2000 Academic Pres s.