Melbourne School of Psychological Sciences, The University of Melbourne, Melbourne, Australia 3010.
Helmholtz Institute, Department of Experimental Psychology, Utrecht University, 3512 Utrecht, the Netherlands.
J Neurosci. 2018 Sep 19;38(38):8243-8250. doi: 10.1523/JNEUROSCI.0736-18.2018. Epub 2018 Aug 13.
Transmission delays in the nervous system pose challenges for the accurate localization of moving objects as the brain must rely on outdated information to determine their position in space. Acting effectively in the present requires that the brain compensates not only for the time lost in the transmission and processing of sensory information, but also for the expected time that will be spent preparing and executing motor programs. Failure to account for these delays will result in the mislocalization and mistargeting of moving objects. In the visuomotor system, where sensory and motor processes are tightly coupled, this predicts that the perceived position of an object should be related to the latency of saccadic eye movements aimed at it. Here we use the flash-grab effect, a mislocalization of briefly flashed stimuli in the direction of a reversing moving background, to induce shifts of perceived visual position in human observers (male and female). We find a linear relationship between saccade latency and perceived position shift, challenging the classic dissociation between "vision for action" and "vision for perception" for tasks of this kind and showing that oculomotor position representations are either shared with or tightly coupled to perceptual position representations. Altogether, we show that the visual system uses both the spatial and temporal characteristics of an upcoming saccade to localize visual objects for both action and perception. Accurately localizing moving objects is a computational challenge for the brain due to the inevitable delays that result from neural transmission. To solve this, the brain might implement motion extrapolation, predicting where an object ought to be at the present moment. Here, we use the flash-grab effect to induce perceptual position shifts and show that the latency of imminent saccades predicts the perceived position of the objects they target. This counterintuitive finding is important because it not only shows that motion extrapolation mechanisms indeed work to reduce the behavioral impact of neural transmission delays in the human brain, but also that these mechanisms are closely matched in the perceptual and oculomotor systems.
神经系统中的传输延迟给准确定位移动物体带来了挑战，因为大脑必须依赖过时的信息来确定物体在空间中的位置。要有效地在当前行动，大脑不仅要补偿在传输和处理感觉信息时损失的时间，还要补偿用于准备和执行运动程序的预期时间。如果不能考虑到这些延迟，将会导致移动物体的位置定位错误和目标错误。在感觉运动系统中，感觉和运动过程紧密结合，这意味着物体的感知位置应该与针对该物体的扫视眼动的潜伏期有关。在这里，我们使用闪光抓取效应（briefly flashed stimuli in the direction of a reversing moving background），即短暂闪光刺激在反向移动背景的方向上的位置误置，来诱导人类观察者（男性和女性）感知视觉位置的移位。我们发现扫视潜伏期和感知位置移位之间存在线性关系，这对这种任务中“行动视觉”和“感知视觉”之间的经典分离提出了挑战，并表明眼动位置表示要么与感知位置表示共享，要么与感知位置表示紧密结合。总之，我们表明，视觉系统既利用即将到来的扫视的空间和时间特征来定位行动和感知中的视觉物体。由于神经传输导致的不可避免的延迟，准确地定位移动物体是大脑面临的计算挑战。为了解决这个问题，大脑可能会实现运动外推，预测物体现在应该在何处。在这里，我们使用闪光抓取效应来诱导感知位置移位，并表明即将到来的扫视的潜伏期预测了它们瞄准的物体的感知位置。这个违反直觉的发现很重要，因为它不仅表明运动外推机制确实可以减少人类大脑中神经传输延迟对行为的影响，而且还表明这些机制在感知和眼动系统中紧密匹配。
