Toward an understanding of auditory evoked cortical event-related potentials: Characteristics and classification

Objective: To investigate the characteristics of auditory evoked cortical ERP components P1-N1-P2 and MMN and explore a practical way for ERP waveform identification and classification. Methods: Thirty right-handed normally hearing volunteers participated in the present study, age ranging from 20 to 40 years old, 14 males and 16 females. All the volunteers reported no history of auditory, neurological or mental disorder. The event related potential (ERP) components (i.e. P1-N1-P2 complex and mismatch negativity (MMN)) were measured using the 128-electrode channels EGI system. Results: Three different categories of ERP responses were classified on the basis of waveform configuration, size of the peak amplitude and the number of peaks together with scalp distribution of MMN. Ten participants (33.3%) had well defined ERP responses, 13 (43.3%) showed moderately defined ERP responses, and seven (23.3%) had poorly defined ERP responses. Although there were no significant differences in P1, P2, and MMN latencies, participants with the poorly defined ERP waves had significantly longer N1 latency than that in subjects with well defined ERP waves. In addition, significantly lower MMN amplitudes were also found in this group. Conclusion: Combining a waveform classification method and the MMN scalp distribution pattern, together with quantitative ERP response analysis, may provide more reliable and practical means for clinical application.