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BACKGROUND AND PURPOSE: The aim of this study was to identify the mechanism underlying the auditory discriminatory process reflected in mismatch negativity (MMN), using time-frequency analysis of single-trial event-related potentials (ERPs). METHODS: Two auditory tones of different probabilities (oddball paradigm) and the same probability (control paradigm) were used. The average dynamic changes in amplitude were evaluated, and the in-phase consistency of the EEG spectrum at each frequency and time window across trials, event-related spectral perturbations (ERSPs), and inter-trial phase coherence (ITC) were computed. RESULTS: Subtraction of the ERPs of standard stimuli from the ERPs of deviant stimuli revealed a clear MMN component in the oddball paradigm. However, no discernible MMN component was observed in the control paradigm. Statistical tests showed that in the oddball paradigm, deviant tones produced significant increases of theta ERSPs and ITC at around 250 ms as compared with the standard tone, while no significant difference between the two stimuli was observed in the control paradigm. CONCLUSIONS: Our results confirm that the auditory discriminatory process reflected in MMN is accompanied by phase resetting and power modulation at the theta frequency.
Discrimination (Psychology) ; Electroencephalography ; Evoked Potentials

BACKGROUND AND PURPOSE: Neuropsychological and neuroimaging studies both suggest that frontal lobe dysfunction is present in migraineurs. Since P3a abnormalities manifest in other diseases associated with attention problems, such as attention deficit hyperactivity disorder, we hypothesized that migraine patients have P3a abnormalities, particularly in the frontal region. METHODS: Event-related potentials were measured using a passive auditory oddball paradigm in 16 female migraineurs (aged 22.9+/-2.0 years, mean+/-SD) during the interictal period and in 16 age-matched healthy females (22.6+/-2.0 years). The amplitudes and latencies were analyzed independently using repeated-measures analysis of variance. Nonparametric statistical testing using a cluster-level randomization method was performed to localize the abnormalities. RESULTS: The mean P3a amplitude at frontal areas during the third trials was significantly lower in migraineurs (1.06 microV) than in controls (1.69 microV, p=0.026). P3a amplitudes were negatively correlated with the duration of the migraine history (r=-0.618, p=0.014). Cluster-based nonparametric statistical analysis showed that the amplitudes over left frontal areas were significantly lower in migraine patients than in controls. CONCLUSIONS: A reduced P3a amplitude of migraineurs reflects attentional deficits and frontal dysfunction. The negative correlation between P3a amplitude and the duration of the migraine history suggests that attentional deficits and frontal dysfunction are either the cause or the result of headache.
Attention Deficit Disorder with Hyperactivity ; Evoked Potentials ; Female ; Frontal Lobe ; Headache ; Humans ; Migraine Disorders ; Neuroimaging ; Oxalates ; Random Allocation