Effect of inverting electrode on mismatch negativity presence for perceptible/imperceptible tonal frequency contrasts

The effect of inverting electrode location and stimulus perceptibility on the presence of the mismatch negativity (MMN) evoked response was investigated in 20 normal-hearing adult females. Perceptible and imperceptible frequency contrasts were employed in an oddball paradigm. The perceptible contrast consisted of an 1122 Hz standard and a 1000 Hz target, while the imperceptible contrast consisted of an 1122 Hz standard and an 1120 Hz target. Data were referenced separately to the tip of the nose, the ipsilateral mastoid, and the mathematical average of the two mastoids. Presence of a response was determined according to strict criteria established a priori. The correspondence between MMN findings and parallel behavioral discrimination data was not systematic. Inverting electrode had an effect of MMN presence. MMNs were more likely to be present for mastoid-referenced data than nose-referenced data. Thus, when using the current paradigm, a mastoid reference is suggested to optimize the detection of the MMN response.