The mismatch negativity evoked by changes in the frequency of an auditory stimulus.

This thesis deals with some of the unknown issues in slow auditory evoked potentials (AEPs). Slow AEPs were recorded in 10 healthy reading subjects. A change in the frequency of the tonebursts elicited an additional negativity--the mismatch negativity (MMN). The amplitude and latency of MMN changed with the magnitude of frequency deviance between stimuli which was varied between 50 and 2000 Hz. The voltage distributions of the MMN and N1 were significantly different from that of the SP. The MMN and N1 had their maximal amplitudes in the fronto-central areas, whereas the maximal amplitude of the SP was recorded frontally. The topographic mapping and statistical analysis of voltage distribution of individual waves enabled us to recognize and differentiate between the possible generators of the MMN, N1 and SP. Both the MMN and N1 are generated in the auditory cortices. The SP is more complexed and may consist of more than one component. (Abstract shortened by UMI.