Pre-attentive Pitch Processing of Harmonic Complex Sounds at Sensor and Source Levels: Comparing Simultaneously Recorded EEG and MEG Data.

Electroencephalography (EEG) and magnetoencephalography (MEG), two of the most widely used tools for studying human brain dynamics, are thought to have varying spatial resolutions. Here, we simultaneously recorded EEG and MEG data from 14 participants to directly compare their sensitivities - at both the sensor and source levels - to the auditory Mismatch Negativity (MMN in EEG and MMNm in MEG) elicited by pitch deviants. At the sensor level, we observed that negative components emerged in early (100-190 ms) and late (260-420 ms) latency windows. These responses displayed a fronto-central distribution in EEG and a centro-parietal distribution in MEG. MEG also yielded larger effect sizes than EEG, likely reflecting differences in signal-to-noise ratio between MEG and EEG. At the source level, our findings support the involvement of a fronto-temporal auditory MMN network. Both EEG and MEG identified generators in the superior temporal gyrus, Heschl's gyrus, interior frontal gyrus, and insular regions. Notably, EEG source localization revealed additional generators in the left superior temporal sulcus not detected by MEG, whereas MEG identified late components generators in the right hemisphere that were not observed with EEG. Taken together, these results suggest that EEG and MEG may provide complementary perspectives on auditory processing. However, given the inherent complexity of comparing data acquired with different methodologies and the limited sample size, our conclusions should be regarded as preliminary.