Separation of mismatch negativity and the N1 wave in the auditory cortex of the cat: a topographic study

Objective: The amplitude distribution of the frequency mismatch negativity (MMN) and that of P1 and N1 components were investigated in cats to reveal their sources in the auditory areas of the neocortex. Methods: Pure tone stimuli were given in a passive oddball paradigm with different degrees of deviance between the standard and deviant tones. Amplitude maps of event-related potential (ERP) components were generated from the responses, recorded in awake, freely moving animals by a chronically implanted epidural electrode matrix, covering both the primary and secondary auditory fields. Results: The P1 and N1 components appeared with highest amplitude on the middle ectosylvian gyrus, while the amplitude maximum of the MMN was ventral and rostral to them on the AII area. Both the latency and the peak amplitude of the MMN depended on the degree of deviance. Conclusions: The MMN is generated in the rostroventral part of the secondary auditory area, well separated from the sources of the P1 and N1 components.