Dipole localization and test-retest reliability of frequency and duration mismatch negativity generator processes.

The mismatch negativity (MMN) is an event related potential component elicited by changes in duration, frequency or intensity of the stimuli during repetitive series of equal standard stimuli. In the present study we compared duration and frequency MMN using dipole source analysis concerning both the test-retest reliability of MMN-amplitudes and the locations of the potential sources. Furthermore, the influence of attention for test-retest-reliability was studied. Therefore, two groups of healthy subjects were investigated with different attentional manipulations. Twenty-one healthy subjects had to perform a visual attention task during the recording and 21 healthy subjects had no additional task to perform. All subjects were studied twice with a time interval of 3 weeks. Test-retest reliability was sufficiently high for the frequency but slightly lower for the duration MMN. The locations of the frequency and duration MMN-dipoles were in the auditory cortex with a more anterior and caudal location for the frequency MMN-dipoles. The latter finding supports the hypothesis that the frequency and duration MMNs have separate neuronal generators.