ATTENTION AND MISMATCH NEGATIVITY

The mismatch negativity (MMN) component of the auditory event-related potential (ERP) is elicited by infrequent, physically deviant stimuli in a sequence of frequent homogeneous stimuli (standards). It has been suggested that the MMN is generated by an automatic (attention-indepe ndent) neural mismatch process with a memory trace that encodes the ph ysical features of the standard stimulus. The proposed MMN independenc e of attention was addressed in the present study. Standard stimuli an d two types of deviant stimuli, differing from standards either in fre quency or intensity, were dichotically presented in random order and a t a very rapid rate. The subject attended either to left- or right-ear stimuli, counting the number of a designated type of deviants in that ear. In the present conditions of very strongly focused attention, th e MMN was elicited even by frequency change in the ignored input strea m, and its amplitude was very similar to that of the MMN elicited by e quivalent deviant stimuli (targets) in the attended input stream. In c ontrast, the MMN to intensity deviation was clearly attenuated in the absence of attention. This effect is, however, probably due to the att ention effect on the MMN generator itself rather than the antecedent s ensory-analysis and -storing functions.