Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Eur J Neurosci. 2010 Dec;32(11):1951-8. doi: 10.1111/j.1460-9568.2010.07456.x. Epub 2010 Oct 29.
How the brain integrates visual information across time into coherent percepts is an open question. Here, we presented two verniers with opposite offset directions one after the other. A vernier consists of two vertical bars that are horizontally offset. When the two verniers are separated by a blank screen (interstimulus interval, ISI), the two verniers are perceived either as two separate entities or as one vernier with the offset moving from one side to the other depending on the ISI. In both cases, their offsets can be reported independently. Transcranial magnet stimulation (TMS) over the occipital cortex does not interfere with the offset discrimination of either vernier. When a grating, instead of the ISI, is presented, the two verniers are not perceived separately anymore, but as 'one' vernier with 'one' fused vernier offset. TMS strongly modulates the percept of the fused vernier offset even though the spatio-temporal position of the verniers is identical in the ISI and grating conditions. We suggest that the grating suppresses the termination signal of the first vernier and the onset signal of the second vernier. As a consequence, perception of the individual verniers is suppressed. Neural representations of the vernier and second vernier inhibit each other, which renders them vulnerable to TMS for at least 300 ms, even though stimulus presentation was only 100 ms. Our data suggest that stimulus features can be flexibly integrated in the occipital cortex, mediated by neural interactions with outlast stimulus presentations by far.
大脑如何将视觉信息在时间上整合为连贯的感知是一个悬而未决的问题。在这里，我们先后呈现了两个具有相反偏移方向的游标。游标由两个垂直的条带组成，它们在水平方向上偏移。当两个游标之间有一个空白屏幕（刺激间隔，ISI）时，两个游标要么被感知为两个独立的实体，要么被感知为一个游标，其偏移从一侧移动到另一侧，这取决于 ISI。在这两种情况下，它们的偏移都可以独立报告。经颅磁刺激（TMS）作用于枕叶皮层不会干扰对任何一个游标偏移的辨别。当呈现光栅而不是 ISI 时，两个游标不再被单独感知，而是被感知为具有“一个”融合游标偏移的“一个”游标。即使在 ISI 和光栅条件下，游标在时空位置上是相同的，TMS 也会强烈调制融合游标偏移的感知。我们认为，光栅抑制了第一个游标终止信号和第二个游标起始信号。因此，对单个游标的感知受到抑制。游标和第二个游标神经表征之间的相互抑制，使得它们在刺激呈现仅 100 毫秒的情况下，容易受到 TMS 的影响，至少持续 300 毫秒。我们的数据表明，刺激特征可以在枕叶皮层中灵活地整合，这是由与刺激呈现相比远为持久的神经相互作用介导的。
