Liu L C, Plomp G, van Leeuwen C, Ioannides A A
Laboratory for Human Brain Dynamics, RIKEN Brain Science Institute (BSI), 2-1 Hirosawa, Wakoshi, Saitama 351-0198, Japan.
Neuroscience. 2006 Sep 1;141(3):1585-97. doi: 10.1016/j.neuroscience.2006.04.062. Epub 2006 Jun 6.
The visual system rapidly completes a partially occluded figure. We probed the completion process by using priming in combination with neuroimaging techniques. Priming leads to more efficient visual processing and thus a reduction in neural activity in relevant brain areas. These areas were studied with high spatial resolution and temporal accuracy with focus on early perceptual processing. We recorded magnetoencephalographic responses from 10 human volunteers in a primed same-different task for test figures. The test figures were preceded by a sequence of two figures, a prime or control figure followed by an occluded figure. The prime figures were one of three possible interpretations of the occluded figures: global and local completions and mosaic interpretation. A significant priming effect was evident: in primed trials as compared with control trials, subjects responded faster and the latency was shorter in the magnetoencephalographic signal for the largest peak between 50 and 300 ms after the occluded figure onset. Tomographic and statistical parametric mapping analyses revealed stages of activation in occipitotemporal areas during occluded figure processing. Notably, we found significantly reduced activation in the right fusiform cortex between 120 and 200 ms after occluded figure onset for primed trials as compared with control trials. We also found significant spatiotemporal differences of local, global and mosaic interpretations for individual subjects but not across subjects. We conclude that modulation of activity in the right fusiform cortex may be a neural correlate of priming in the interpretation of an occluded figure, and that this area acts as a hub for different occluded figure interpretations in this early stage of perception.
视觉系统能快速补全部分遮挡的图形。我们通过启动效应与神经成像技术相结合的方式来探究这一补全过程。启动效应会使视觉处理更高效，从而降低相关脑区的神经活动。我们以早期感知处理为重点，运用高空间分辨率和时间精度对这些脑区进行了研究。我们记录了10名人类志愿者在针对测试图形的启动效应相同 - 不同任务中的脑磁图反应。测试图形之前有两个图形序列，一个启动图形或控制图形，随后是一个遮挡图形。启动图形是遮挡图形三种可能的解释之一：全局和局部补全以及镶嵌解释。显著的启动效应很明显：与控制试验相比，在启动试验中，受试者反应更快，并且在遮挡图形出现后50至300毫秒之间最大峰值的脑磁图信号潜伏期更短。断层扫描和统计参数映射分析揭示了在遮挡图形处理过程中枕颞区的激活阶段。值得注意的是，与控制试验相比，我们发现在启动试验中，遮挡图形出现后120至200毫秒之间右侧梭状回皮质的激活显著降低。我们还发现了个体受试者在局部、全局和镶嵌解释方面存在显著的时空差异，但不同受试者之间没有。我们得出结论，右侧梭状回皮质活动的调制可能是遮挡图形解释中启动效应的神经关联，并且在这个早期感知阶段，该区域充当了不同遮挡图形解释的枢纽。
