Clinical Utility of Visual Mismatch Negativity in Children with Mental Retardation

Abstract

Background: The mismatch negativity (MMN) component is an event-related potential (ERP) that can be elicited by any changes, particularly in the acoustic environment. Recently, several studies have obtained visual MMN. MMN is said to reflect the process by which stimuli are detected automatically. We have reported the developmental changes of visual MMN in children. In this study, we present the clinical utility of MMN in children with mental retardation. Methods: The subjects were 29 mentally retarded patients. Electroencephalograms were recorded from Fz, Cz, Pz and Oz electrode locations (international 10-20 method) with reference to the earlobe. MMNs were measured by using different waveforms by subtracting the ERP to the frequent stimuli from that to rare stimuli. We compared the latencies of visual MMN between normal and mental retarded subjects. Results: In this study, the visual MMN latency of mentally retarded patients was longer than that of normal subjects. In particular, there was a significant difference in the visual MMN latency between normal and mentally retarded children above six years of age. Conclusion: Clinically, age-related changes of visual MMN in normal subjects are very important in the assessment of the maturation of pre-attentional processing. Our results suggest that some mentally retarded patients exhibit impairment of pre-attentional processing in the visual cognitive function.