Macquarie Centre for Cognitive Science, Macquarie University, Sydney, NSW 2109, Australia.
Neurosci Lett. 2010 Sep 20;482(1):71-5. doi: 10.1016/j.neulet.2010.07.010. Epub 2010 Jul 12.
The mismatch negativity (MMN) component of the auditory event-related potential (ERP) reflects the process of change detection in the auditory system. The present study investigated the effect of deviance direction (increment vs. decrement) and calculation method (traditional vs. same-stimulus) on the amplitude of MMN. MMN was recorded for increments and decrements in frequency and duration in 20 adults. The stimuli (standard/deviant) were 250 Hz/350 Hz (frequency MMN) and 200 ms/300 ms (duration MMN) for increment MMN and vice versa for decrement MMN. Amplitude of MMN was calculated in two ways: the traditional method (subtracting ERP to the standard from the deviant presented in the same block) and the same-stimulus method (subtracting ERP to identical stimuli presented as standard in one block and deviant in another block). We found that increments in frequency produced higher MMN amplitudes compared to decrements for both methods of calculation. For duration deviance, the decrement MMN was absent in the traditional method, while the decrement and increment MMN did not differ for the same-stimulus method. These findings suggest that the brain processes frequency increments and decrements in different ways. The results also suggest the use of same-stimulus method for the calculation of duration MMN when long duration stimuli are used.
失匹配负波（MMN）是听觉事件相关电位（ERP）的一个成分，反映了听觉系统中的变化检测过程。本研究考察了偏离方向（递增与递减）和计算方法（传统与同刺激）对 MMN 振幅的影响。研究记录了 20 名成年人在频率和时长上递增和递减的 MMN。刺激（标准/偏离）为 250Hz/350Hz（频率 MMN）和 200ms/300ms（时长 MMN），递增 MMN 的情况反之亦然，递减 MMN 的情况也一样。MMN 的振幅通过两种方法计算：传统方法（在同一块中，从标准刺激减去偏离刺激的 ERP）和同刺激方法（在一个块中，将相同的刺激作为标准减去 ERP，在另一个块中作为偏离刺激减去 ERP）。我们发现，对于两种计算方法，频率递增都会产生比递减更高的 MMN 振幅。对于时长偏离，传统方法中不存在时长递减 MMN，而对于同刺激方法，时长递减和递增 MMN 没有差异。这些发现表明大脑以不同的方式处理频率的递增和递减。结果还表明，当使用长时间刺激时，应该使用同刺激方法来计算时长 MMN。
