Mismatch negativity of the color modality during a selective attention task to auditory stimuli in children with mental retardation

Event-related potentials (ERPs) in response to a stimulus change in the visual color modality were recorded in normal subjects and children with mental retardation (MR) under selective attention conditions with auditory stimuli. The paradigm included the presentation of a standard (blue color screen, B) or deviant (red, R, or greenish blue color screen, GB) visual stimulus, and a target or non-target tone burst stimulus. In Experiment 1, negativity of the subtracted waveform in response to visual stimuli with a latency of 250-280 ms was clearly observed in the ERPs of normal adults. These potentials prominently appeared at posterior sites in one condition, for which the deviant was GB, but were frontal site-dominant for the other condition. A P300 response to visual deviance was not observed in the GB-B paradigm and the subtracted negativity for this paradigm seemed to be more evident than that for the R-B paradigm. The subtracted negativities could be detected in the range of 180-400 ms after the stimulus onset in control children for the GB-B paradigm. The grand average waves of subtracted ERPs in normal children showed a similar distribution to that in normal adults. Similar subtracted potentials could be recorded with the same paradigm in children with MR, however, the negativities were different in waveform and spatial distribution than in controls. Therefore, the subtracted negativity of the present visual modality represented the analogue of the auditory mismatch negativity (MMN), and so-called 'visual MMN' was detectable in children and even in MR patients when the selective attention was directed to other stimuli.