Bistable perception refers to a broad class of dynamically alternating visual illusions that result from ambiguous images. These illusions provide a powerful method to study the mechanisms that determine how visual input is integrated over space and time. Binocular rivalry occurs when subjects view different images in each eye, and a similar experience called stimulus rivalry occurs even when the left and right images are exchanged at a fast rate. Many previous studies have identified with fMRI a network of cortical regions that are recruited during binocular rivalry, relative to non-rivalrous control conditions (termed replay) that use physically changing stimuli to mimic rivalry. However, we show here for the first time that additional cortical areas are activated when subjects experience rivalry with interocular grouping. When interocular grouping occurs, activation levels broadly increase, with a slight shift towards right hemisphere lateralization. Moreover, direct comparison of binocular rivalry with and without grouping highlights strong focused activity in the intraparietal sulcus and lateral occipital areas, such as right-sided retinotopic visual areas LO1 and IP2, as well as activity in left-sided visual areas LO1, and IP0-IP2. The equivalent analyses for comparable stimulus (eye-swap) rivalry showed very similar results; the main difference is greater recruitment of the right superior parietal cortex for binocular rivalry, as previously reported. Thus, we found minimal interaction between the novel networks isolated here for interocular grouping, and those previously attributed to stimulus and binocular rivalry. We conclude that spatial integration (i.e,. image grouping/segmentation) is a key function of lateral occipital/intraparietal cortex that acts similarly on competing binocular stimulus representations, regardless of fast monocular changes.

双稳态感知是指由模棱两可的图像导致的一类动态交替的视觉错觉。这些幻觉提供了一种强大的方法来研究确定视觉输入如何随时间和空间整合的机制。当对象在每只眼睛中观看不同的图像时，就会发生双眼竞争，即使左右图像的交换速度很快，也会发生类似的被称为刺激竞争的经历。相对于使用物理变化的刺激来模仿竞争的非竞争性控制条件（称为重播），以前的许多研究已经通过功能磁共振成像（fMRI）确定了在双眼竞争中募集的皮质区域网络。但是，我们第一次在这里显示，当受试者与眼内分组竞争时，额外的皮质区域会被激活。当发生眼内分组时，激活水平广泛增加，向右半球偏侧化略有转移。此外，直接比较带和不带分组的双眼竞争，突出显示了在顶壁沟和枕骨外侧区域（如右侧视网膜视网膜视区LO1和IP2）中的强烈聚焦活动，以及左侧视区LO1和IP0中的活动。 -IP2。相当的刺激（眼神交换）竞争的等效分析显示出非常相似的结果。如前所述，主要区别在于可以更好地募集右上顶叶皮层用于双眼竞争。因此，我们发现这里隔离的用于眼内分组的新型网络与先前归因于刺激和双眼竞争的网络之间的交互作用最小。我们得出的结论是，空间整合（即