Background and Aim: Mismatch negativity (MMN) is one of auditory evoked potentials that occurs about 100-250 ms after stimulus onset. The MMN waveform is elicited by a discriminateable change in a sequence of repetitive homogenous stimuli. This change can be in intensity level, frequency, or duration of auditory stimuli. The purpose of this study was to obtain MMN waveform using tonal stimuli and to investigate its changes during changes in age.
Materials and Methods: The study was prescriptive-analytic cross-sectional. The participants were sixty children aged 4 to 9 year.The Stimuli were at 80 dB pe SPL. A 1000Hz tone and a 1500 Hz tone were used as standard and deviant stimuli, respectively. Probability of deviant stimuli was 20%. Trials were recorded using surface electrode placed at four locations on the head.
Results: The MMN waveform does not exist in 22.5% of the children. Also, determining of MMN peak in 22.5% was not exactly possible. In other subjects, a significant negative correlation was observed between latency of MMN and age, but not for age and amplitude for this negativity.
Conclusion: This study confirms that the MMN may not be seen in normal people. Also there are maturational changes in MMN waveform.