Cognition and Action Research Group, Human Technology Research Institute, National Institute of Advanced Industrial Science and Technology Tsukuba, Japan.
Front Hum Neurosci. 2013 Jun 12;7:267. doi: 10.3389/fnhum.2013.00267. eCollection 2013.
Visual mismatch negativity (MMN) is an event-related brain potential (ERP) component that is elicited by prediction-incongruent events in successive visual stimulation. Previous oddball studies have shown that visual MMN in response to task-irrelevant deviant stimuli is insensitive to the manipulation of task difficulty, which supports the notion that visual MMN reflects attention-independent predictive processes. In these studies, however, visual MMN was evaluated in deviant-minus-standard difference waves, which may lead to an underestimation of the effects of task difficulty due to the possible superposition of N1-difference reflecting refractory effects. In the present study, we investigated the effects of task difficulty on visual MMN, less contaminated by N1-difference. While the participant performed a size-change detection task regarding a continuously-presented central fixation circle, we presented oddball sequences consisting of deviant and standard bar stimuli with different orientations (9.1 and 90.9%) and equiprobable sequences consisting of 11 types of control bar stimuli with different orientations (9.1% each) at the surrounding visual fields. Task difficulty was manipulated by varying the magnitude of the size-change. We found that the peak latencies of visual MMN evaluated in the deviant-minus-control difference waves were delayed as a function of task difficulty. Therefore, in contrast to the previous understanding, the present findings support the notion that visual MMN is associated with attention-demanding predictive processes.
视觉失匹配负波（MMN）是一种事件相关脑电位（ERP）成分，它是由连续视觉刺激中的预测不一致事件引起的。以前的Oddball 研究表明，对与任务无关的偏差刺激的视觉 MMN 对任务难度的操作不敏感，这支持了视觉 MMN 反映注意力独立预测过程的观点。然而，在这些研究中，视觉 MMN 是在偏差-标准差值波中进行评估的，由于可能存在反映反射性效应的 N1 差值的叠加，这可能会导致对任务难度效应的低估。在本研究中，我们研究了任务难度对视觉 MMN 的影响，这种影响较少受到 N1 差值的干扰。当参与者执行一个关于连续呈现的中央固定圆的大小变化检测任务时，我们呈现了由不同方向的偏差和标准棒刺激组成的 Oddball 序列（9.1%和 90.9%），以及由不同方向的 11 种控制棒刺激组成的等概率序列（9.1%每种）在周围的视野中。任务难度通过改变大小变化的幅度来操纵。我们发现，在偏差-控制差值波中评估的视觉 MMN 的峰值潜伏期随着任务难度的增加而延迟。因此，与之前的理解相反，本研究结果支持了视觉 MMN 与注意力要求高的预测过程有关的观点。
