Automatic auditory processing and event-related brain potentials in persons with mental retardation

Measuring event-related brain potentials, this study examined automatic aud itory processing in adults with and without mental retardation. Using an au ditory oddball paradigm under an inattentive condition, we anticipated that an enhanced negative potential would be followed by a relatively small pos itive potential. The former was considered as the mismatch negativity and t he latter as the P3a. Retarded adults (1 woman, 6 men, defined as a range o f moderate to profound retardation) and 8 nonretarded (2 women, 6 men) adul ts participated. The mismatch negativity showed smaller amplitudes and grea ter latencies for retarded persons than those for nonretarded adults, where as the P3a for the groups was comparable. The results may suggest malfuncti on of automatic auditory change-detection of the brain in mentally retarded persons.