Neonatal frequency discrimination in 250-4000-Hz range: Electrophysiological evidence

Objective: The precision of sound frequency discrimination in newborn infants in the 250-4000-Hz frequency range was determined using the neonatal electrophysiological mismatch response (MMR), the infant equivalent of adult mismatch negativity (MMN). Methods: The electroencephalogram (EEG) was recorded in I 1 full-term sleeping newborn infants mostly in active sleep (67 % of the time). Pure tones were presented through loudspeakers in an oddball paradigm with a 800-ms stimulus onset asynchrony (SOA). Each stimulus block contained a standard (p = 0.76) of 250, 1000, or 4000 Hz in frequency (in separate blocks) and deviants with a frequency change of either 5% or 20% of the standard (p = 0.12 of each). Results: A positive ERP deflection was found at 200-300 ms from stimulus onset in response to the 20% deviation from the 250, 1000, and 4000 Hz standard frequencies. The amplitude of the response in the 200-300 ms time window was significantly larger for the 20% than 5% deviation. Conclusions: We observed in newborn infants automatic frequency discrimination as reflected by a positive MMR. The newborns were able to discriminate frequency change of 20% in the 250-4000-Hz frequency range, whereas the discrimination of the 5% frequency change was not statistically confirmed. Significance: The present data hence suggest that the neonatal frequency discrimination has lower resolution than that in adult and older children data. (c) 2006 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved