ABNORMAL FREQUENCY MISMATCH NEGATIVITY IN MENTALLY-RETARDED CHILDREN AND IN CHILDREN WITH DEVELOPMENTAL DYSPHASIA

The auditory event-related potential waveform termed ''mismatch negati vity'' was examined in 12 mentally retarded children with delayed deve lopment of speech and language (aged 5-8 years) and in 13 children wit h developmental dysphasia (aged 5-9 years). The mismatch negativity wa ves were elicited with pure sine-wave tone stimuli using the oddball p aradigm. We measured the peak latency and peak amplitude of mismatch n egativity responses to frequency (500/553 Hz) difference, The mismatch negativity patterns were compared with those of 10 children with norm al development of linguistic skills (aged 5-9 years). Ln both the ment ally retarded and dysphasic groups, the peak amplitude of the frequenc y mismatch negativity was significantly attenuated when compared with the control group, but no significant difference was observed between the mentally retarded and dysphasic groups. Attenuated frequency misma tch negativity was related to impairment of linguistic skills irrespec tive of the child's cognitive skills, Because the mismatch negativity response reflects central auditory processing and is modal specific fo r auditory stimuli, this change-specific response can serve as an obje ctive tool to elucidate central auditory deficits in children.