Abstract
Event-related brain potentials in a passive two-or three-stimulus auditory oddball were recorded from seven adults with moderate or severe mental retardation, and were compared with data from normal subjects. In Experiment 1, subjects were presented with a random sequence of 1000Hz (p=.8) and 2000Hz (p=.2) tones. Two of the seven retarded subjects and all of the four normal subjects showed N2-P3 to the rare tone. Five retarded subjects showed only negative waves. In Experiment 2, the stimulus sequence comprised a frequent tones (1000Hz : p=.7), rare tones (2000Hz : p=.15) and novel sounds (noise : p=.15). Five of the seven retarded and all of the six normal subjects showed positive waves to novel stimuli. It is suggested that novel stimuli may elicit P3 (P3a) even in severely retarded people.
