Clark Kait, Appelbaum L Gregory, van den Berg Berry, Mitroff Stephen R, Woldorff Marty G
Center for Cognitive Neuroscience and School of Psychology, Cardiff University, Cardiff CF10 3AT, United Kingdom.
Center for Cognitive Neuroscience and Department of Psychiatry, Duke University Medical Center, Durham, North Carolina 27708, and.
J Neurosci. 2015 Apr 1;35(13):5351-9. doi: 10.1523/JNEUROSCI.1152-14.2015.
Practice can improve performance on visual search tasks; the neural mechanisms underlying such improvements, however, are not clear. Response time typically shortens with practice, but which components of the stimulus-response processing chain facilitate this behavioral change? Improved search performance could result from enhancements in various cognitive processing stages, including (1) sensory processing, (2) attentional allocation, (3) target discrimination, (4) motor-response preparation, and/or (5) response execution. We measured event-related potentials (ERPs) as human participants completed a five-day visual-search protocol in which they reported the orientation of a color popout target within an array of ellipses. We assessed changes in behavioral performance and in ERP components associated with various stages of processing. After practice, response time decreased in all participants (while accuracy remained consistent), and electrophysiological measures revealed modulation of several ERP components. First, amplitudes of the early sensory-evoked N1 component at 150 ms increased bilaterally, indicating enhanced visual sensory processing of the array. Second, the negative-polarity posterior-contralateral component (N2pc, 170-250 ms) was earlier and larger, demonstrating enhanced attentional orienting. Third, the amplitude of the sustained posterior contralateral negativity component (SPCN, 300-400 ms) decreased, indicating facilitated target discrimination. Finally, faster motor-response preparation and execution were observed after practice, as indicated by latency changes in both the stimulus-locked and response-locked lateralized readiness potentials (LRPs). These electrophysiological results delineate the functional plasticity in key mechanisms underlying visual search with high temporal resolution and illustrate how practice influences various cognitive and neural processing stages leading to enhanced behavioral performance.
练习可以提高视觉搜索任务的表现；然而，这种提高背后的神经机制尚不清楚。反应时间通常会随着练习而缩短，但刺激-反应处理链的哪些组成部分促成了这种行为变化呢？搜索表现的提高可能源于各种认知处理阶段的增强，包括（1）感觉处理、（2）注意力分配、（3）目标辨别、（4）运动反应准备和/或（5）反应执行。当人类参与者完成一个为期五天的视觉搜索实验方案时，我们测量了事件相关电位（ERP），在该方案中，他们报告椭圆阵列中颜色突出目标的方向。我们评估了行为表现以及与各个处理阶段相关的ERP成分的变化。练习后，所有参与者的反应时间都减少了（而准确性保持一致），并且电生理测量结果显示几个ERP成分有调节变化。首先，150毫秒时早期感觉诱发的N1成分的双侧振幅增加，表明对阵列的视觉感觉处理增强。其次，负极性对侧后部分成分（N2pc，170 - 250毫秒）出现得更早且幅度更大，表明注意力定向增强。第三，持续对侧后负性成分（SPCN，300 - 400毫秒）的振幅降低，表明目标辨别变得更容易。最后，练习后观察到运动反应准备和执行更快，刺激锁定和反应锁定的侧化准备电位（LRP）的潜伏期变化表明了这一点。这些电生理结果以高时间分辨率描绘了视觉搜索关键机制中的功能可塑性，并说明了练习如何影响导致行为表现增强的各种认知和神经处理阶段。
