Sams M, Paavilainen P, Alho K, Näätänen R
Electroencephalogr Clin Neurophysiol. 1985 Nov;62(6):437-48. doi: 10.1016/0168-5597(85)90054-1.
Auditory stimulus blocks were presented to 6 subjects. 80% of the stimuli in each block were standards of 1000 Hz and 20% were deviants of either 1002 Hz, 1004 Hz, 1008 Hz, 1016 Hz or 1032 Hz, one deviant type in each block. The constant interstimulus interval was 1 sec and the order of the stimuli was randomized. The subject was instructed either to ignore the deviant stimuli (ignore condition) or to press a response key to them (discrimination condition). In the ignore condition, an ERP component called the mismatch negativity (MMN), with a peak latency of approximately 170 msec, was elicited by those deviants exceeding the discrimination threshold (1016 Hz and 1032 Hz) and also those at the threshold (1008 Hz) tended to elicit a small MMN. In the discrimination condition, in addition to MMN, another negative component, N2b, was elicited by the detected deviants. This component had a somewhat longer latency than, and its midline distribution was posterior to, the MMN. The present results are in line with the hypothesis according to which the MMN component reflects the activation of cerebral mechanisms of passive discrimination, those which cause us to become aware of occasional changes in unattended stimulus sequences. In the discrimination condition, N2b and the slow parietal positivity were dominant features of the ERPs elicited by the detected suprathreshold deviants. The data obtained at the discrimination threshold specifically associate the parietal positivity with becoming aware of stimulus change since those deviants which were detected elicited this positivity whereas there was none to those (physically identical) deviants which remained undetected.
向6名受试者呈现听觉刺激组块。每个组块中80%的刺激是1000赫兹的标准刺激，20%是1002赫兹、1004赫兹、1008赫兹、1016赫兹或1032赫兹的偏差刺激，每个组块有一种偏差刺激类型。恒定的刺激间隔为1秒，刺激顺序是随机的。受试者被指示要么忽略偏差刺激（忽略条件），要么对其按下反应键（辨别条件）。在忽略条件下，那些超过辨别阈值（1016赫兹和1032赫兹）的偏差刺激会引发一种称为失配负波（MMN）的事件相关电位成分，其峰值潜伏期约为170毫秒，并且那些处于阈值（1008赫兹）的刺激也往往会引发一个小的MMN。在辨别条件下，除了MMN之外，被检测到的偏差刺激还会引发另一个负性成分N2b。该成分的潜伏期比MMN稍长，其在中线的分布位于MMN之后。目前的结果符合这样一种假设，即MMN成分反映了被动辨别的大脑机制的激活，这些机制使我们能够意识到未被注意的刺激序列中的偶尔变化。在辨别条件下，N2b和顶叶慢正波是由检测到的阈上偏差刺激引发的事件相关电位的主要特征。在辨别阈值处获得的数据特别将顶叶正波与意识到刺激变化联系起来，因为那些被检测到的偏差刺激引发了这种正波，而对于那些（物理上相同）未被检测到的偏差刺激则没有这种正波。
