The characteristics of mismatch negativity (MMN)
elicited by dichotic stimulation were examined using frequency-deviant
stimuli presented to the right, to the left, or to both
sides. The experiment was run twice, once using earphones
and once using loudspeakers in free field. With both modes
of stimulation, deviants presented in the left, right,
or both ears, or tones that were switched between ears,
elicited comparable MMNs, with a peak latency of about
180 ms. With earphones, the amplitude of the MMN was bigger
at the frontal-lateral right hemisphere sites than at the
homologous left-hemisphere sites for all deviance conditions.
Scalp current density analysis revealed that deviance in
the right side elicited bilaterally equivalent frontal
current sinks and a trend towards stronger contralateral
current sources at the mastoid sites. In contrast, left
side deviance elicited frontal sinks and temporal current
sources stronger over the right hemiscalp. These results
are compatible with the multiple-generator model of MMN.
The attention-related role of the MMN is discussed, suggesting
comparable attention mechanisms for vision and audition.