Passive long-latency event-related potentials in mental retardation.

Long-latency auditory event-related potentials (ERPs) were passively recorded in ten mental retardates and ten age-matched normal controls. Patients were mildly to moderately retarded and had epilepsy controlled with monotherapy, ERPs were recorded from CA-A1+A2, with 1000 and 3000 Hz tones in an "oddball" paradigm. Latency and amplitude of N1, N2, P2, and P3 components were compared in controls and retardates. All ten patients had reproducible AEPs, but these were attenuated in amplitude in four, although amplitudes did not differ significantly from controls. P3 was prolonged in latency in four patients, but patients and controls did not differ significantly. AEP latency and amplitude was not correlated with degree of retardation. These findings suggest that "cognitive" evoked potentials an be recorded passively in persons with impaired cognition, but are not correlated with intellectual ability and may not reflect specific cognitive functions.