The effect of perceptual grouping on the mismatch negativity

The mismatch negativity (MMN) was used as a probe to evaluate changes, with age, of transient auditory memory. Subjects win 16 young (M = 23 years) an d 16 old (M = 72 years) people. Standard auditory stimuli were presented in trains of eight tones (1000 Hz) with either a 1-s or 8-s intertrain interv al (ITI). Occasionally, the first stimulus of a train was replaced with a 1 200 Hz tone (deviant). The MMN was recorded while subjects watched a silent movie and ignored the sounds. Both groups of subjects showed an MMN respon se to deviant stimuli under the 1-s ITI condition, but MMNs were only seen for some subjects under the 8-s ITI condition. After MMN recording, subject s performed a discrimination task to the tones used for recording MMNs. Acc uracy for both groups was near 100% at both ITIs. These results suggest tha t generation of MMN is a function of the perceptual grouping of the acousti cal stimuli and that the integrity of perceptual grouping may be maintained with increased age.