Institut für Psychologie, Universität Regensburg, Regensburg, Germany.
PLoS One. 2013;8(1):e54085. doi: 10.1371/journal.pone.0054085. Epub 2013 Jan 10.
Human observers tend to group oriented line segments into full contours if they follow the Gestalt rule of 'good continuation'. It is commonly assumed that contour grouping emerges automatically in early visual cortex. In contrast, recent work in animal models suggests that contour grouping requires learning and thus involves top-down control from higher brain structures. Here we explore mechanisms of top-down control in perceptual grouping by investigating synchronicity within EEG oscillations. Human participants saw two micro-Gabor arrays in a random order, with the task to indicate whether the first (S1) or the second stimulus (S2) contained a contour of collinearly aligned elements. Contour compared to non-contour S1 produced a larger posterior post-stimulus beta power (15-21 Hz). Contour S2 was associated with a pre-stimulus decrease in posterior alpha power (11-12 Hz) and in fronto-posterior theta (4-5 Hz) phase couplings, but not with a post-stimulus increase in beta power. The results indicate that subjects used prior knowledge from S1 processing for S2 contour grouping. Expanding previous work on theta oscillations, we propose that long-range theta synchrony shapes neural responses to perceptual groupings regulating lateral inhibition in early visual cortex.
人类观察者往往会将具有特定朝向的线段组合成完整的轮廓，如果这些线段符合“良好连续”的格式塔规则。通常认为轮廓分组会在早期视觉皮层中自动出现。相比之下，动物模型的最新研究表明，轮廓分组需要学习，因此涉及来自大脑更高区域的自上而下的控制。在这里，我们通过研究 EEG 振荡中的同步性来探索知觉分组中的自上而下控制机制。人类参与者以随机顺序看到两个微 Gabor 数组，并被要求指出第一个（S1）或第二个刺激（S2）是否包含具有共线对齐元素的轮廓。与非轮廓 S1 相比，轮廓 S1 产生了更大的后刺激β功率（15-21 Hz）。轮廓 S2 与后 alpha 功率（11-12 Hz）和额-后 theta（4-5 Hz）相位耦合的前刺激减少有关，但与后刺激β功率增加无关。结果表明，受试者在 S2 轮廓分组中使用了 S1 处理的先验知识。在以前关于 theta 振荡的研究基础上，我们提出长程 theta 同步性塑造了对感知分组的神经反应，从而调节了早期视觉皮层中的侧抑制。
