We report two main results:
There are no significant early differences in the processing of congruent and incongruent audiovisual action sequences. The earliest difference between congruent and incongruent audiovisual stimuli occurs between 240 and 280 ms after stimulus onset in the left temporal region. Between 340 and 420 ms, semantic congruence modulates responses in central and right frontal areas. Late differences (after 460 ms) occur bilaterally in frontal areas.
Source localisation (dipole modelling and LORETA) reveals that an extended network encompassing inferior frontal, temporal, parasaggital, and superior parietal sites are simultaneously active between 180 and 420 ms to process auditory-visual action sequences. Early activation (before 120 ms) can be explained by activity in mainly sensory cortices.
The simultaneous activation of an extended network between 180 and 420 ms is consistent with models that posit parallel processing of complex action sequences in frontal, temporal and parietal areas rather than models that postulate hierarchical processing in a sequence of brain regions.