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Differential changes in frontal and sub-temporal components of mismatch negativity
T Baldeweg1, J D Williams, J H Gruzelier
1Division of Neuroscience and Psychological Medicine, Imperial College School of Medicine, Charing Cross Hospital, London, UK. T.Baldeweg@ich.ucl.ac.uk
Abstract:
Novel evidence is reported showing changes in the mismatch negativity (MMN) event-related potential (ERP) that followed a different time course in frontal and sub-temporal (mastoid) electrodes. MMN recorded in frontal electrode sites, assumed to originate predominantly in the superior temporal gyrus, showed amplitude enhancement from the first to the second recording block. In contrast, the amplitude of the sub-temporal, mastoid component (termed mismatch positivity, MMP) diminished. In addition to these changes in the MMN elicited by tone duration deviants, there were also significant changes in the ERP to the standard stimulus. The positivity in the standard ERP between 50 and 150 ms increased in bilateral mastoid electrodes but showed no reliable change in frontal electrodes. This suggests that more than one generator underpins the two mismatch components, and that the sub-temporal mismatch component does not only represent a polarity reversal of the main MMN component in the superior temporal gyrus.
Insights
Mismatch negativity (MMN) event-related potentials (ERPs) show distinct temporal changes in frontal and sub-temporal electrodes. This suggests separate neural generators for auditory processing components.
Area of Science:
- Neuroscience
- Auditory Neuroscience
- Cognitive Neuroscience
Background:
- Mismatch negativity (MMN) is an event-related potential (ERP) reflecting automatic auditory change detection.
- Previous studies often assume a single generator for MMN, primarily in the superior temporal gyrus.
Purpose of the Study:
- To investigate the distinct temporal dynamics of MMN components recorded at frontal and sub-temporal (mastoid) electrode sites.
- To explore the underlying neural generators of auditory change detection.
Main Methods:
- Recording of mismatch negativity (MMN) and standard auditory event-related potentials (ERPs).
- Analysis of amplitude changes over time in frontal and mastoid electrode sites.
- Comparison of ERPs elicited by tone duration deviants and standard stimuli.
Main Results:
- Frontal MMN amplitude enhanced across recording blocks, while sub-temporal MMN (mismatch positivity, MMP) amplitude diminished.
- Standard ERPs showed increased positivity in mastoid electrodes (50-150 ms) but not frontal electrodes.
- Differential changes suggest distinct temporal courses and generators for frontal and sub-temporal mismatch responses.
Conclusions:
- Auditory change detection involves multiple neural generators, not solely the superior temporal gyrus.
- The sub-temporal mismatch component (MMP) likely arises from distinct neural sources compared to the frontal MMN.
- These findings challenge the notion of a single generator for MMN and highlight the complexity of auditory processing.