Maturation of the auditory evoke potentials with age: data from a pilot study

Introduction Evoke potentials have been investigated as a surrogate marker of integrity of the developing brain. Mis-match negativity(MMN) is an auditory evoke potential that has been recorded in healthy and at-risk infants. This pilot study was performed to understand the change in amplitude of MMN with advancing age during infancy.

Method A prospective follow up study was performed in healthy infants. A wearable EEG cap was used for data aquisition. An OddBall paradigm was used to record the auditory evoked potential. A 16 minute EEG record was performed in all babies at 2 months. This was repeated at 6, 8, and 12 months in different consecutive groups of infants. The trend in change in the amplitude in healthy infants was evaluated for the different age-group categories. The amplitude of MMN was claculated for the Cz electrode.

Results Eleven, four and eight sets of records performed consecutively at 2 and 6, 2-8 and 2-12 month intervals were analysed. The mean amplitude of MMN over Cz at 2 months was -1.93(SD 5.75). The mean amplitudes were -1.64(SD 2.88) at 6 months, -8.73 (SD 2.88) at 8 months and -1.53 for 12 months. The mean difference was statistically significant only in those who repeated evealuation at 8 months (p=0.024).

Discussion These findings suggest change in the amplitude of MMN with increasing age. In the sub group analysis, the best variability in amplitude was seen when the record was repeated at 8 months of age. These findings need replication in a larger scale study.