Mismatch negativity: the contribution of differences in the refractoriness of stimulus-specific neuron populations.

Mismatch negativity (MMN) is a component of auditory evoked potentials associated with rare changes in acoustic stimulation. Mismatch negativity is usually interpreted as an automatic response from a "changes detector" based on comparison of an incoming stimulus and the representation of preceding stimulation in memory. However, some investigators take the view that mismatch negativity is explained by simpler processes, associated with neuronal refractoriness. The existence of "genuine" mismatch negativity was confirmed, though the question of the contribution of refractoriness to traditional mismatch negativity remained open. The present study uses an experimental design allowing the hypothetical sources of mismatch negativity to be discriminated. A contribution to mismatch negativity associated with neuronal refractoriness was demonstrated; this decreased with increases in the probability of presentation of a deviant stimulus and became negligible at a probability of 15%. Thus, classically interpretable mismatch negativity can be obtained either by using a method excluding the contribution of refractoriness or by using "safe" deviant stimulus presentation probabilities.