Evidence for the different additivity of the temporal and frontal generators of mismatch negativity: a human auditory event-related potential study.

The auditory sensory-memory mechanisms in the human brain were investigated using the mismatch negativity (MMN) component of the event-related potential. MMNs were recorded to stimuli deviating from the repetitive standard stimuli simultaneously either in one or two features (frequency, intensity). If the processing of these two features is independent of each other, the MMN to the double deviant should equal the sum of the MMNs elicited by the corresponding single deviants. The double-deviant MMNs were found to be additive at the electrode sites below the Sylvian fissure but not at the frontal scalp areas. The results suggest that the temporal subcomponent of MMN is additive whereas the frontal is non-additive. The pattern of results was similar in ignore and attend conditions, suggesting that the components were not attentionally modulated.