Melbourne School of Psychological Sciences, The University of Melbourne, Melbourne, VIC, Australia.
Melbourne School of Psychological Sciences, The University of Melbourne, Melbourne, VIC, Australia; Department of Psychology, University of Cologne, Cologne, Germany.
Cortex. 2021 May;138:191-202. doi: 10.1016/j.cortex.2021.02.008. Epub 2021 Feb 19.
Establishing the real-time position of a moving object poses a challenge to the visual system due to neural processing delays. While sensory information is travelling through the visual hierarchy, the object continues moving and information about its position becomes outdated. By extrapolating the position of a moving object along its trajectory, predictive mechanisms might effectively decrease the processing time associated with these objects. Here, we use time-resolved decoding of electroencephalographic (EEG) data from an apparent motion paradigm to demonstrate the interaction of two separate predictive mechanisms. First, we reveal predictive latency advantages for position representations as soon as the second object in an apparent motion sequence - even before the stimulus contains any physical motion energy. This is consistent with the existence of omni-directional, within-layer waves of sub-threshold activity that bring neurons coding for adjacent positions closer to their firing threshold, thereby reducing the processing time of the second stimulus in one of those positions. Second, we show that an additional direction-specific latency advantage emerges from the third sequence position onward, once the direction of the apparent motion stimulus is uniquely determined. Because the receptive fields of early visual areas are too small to encompass sequential apparent motion positions (as evidenced by the lack of latency modulation for the second stimulus position), this latency advantage most likely arises from descending predictions from higher to lower visual areas through feedback connections. Finally, we reveal that the same predictive activation that facilitates the processing of the object in its expected position needs to be overcome when the object's trajectory unexpectedly reverses, causing an additional latency disadvantage for stimuli that violate predictions. Altogether, our results suggest that two complementary mechanisms interact to form and revise predictions in visual motion processing, modulating the latencies of neural position representations at different levels of visual processing.
由于神经处理延迟，移动目标的实时位置对视觉系统构成挑战。当感觉信息在视觉层次结构中传输时，物体继续移动，其位置信息变得过时。通过沿物体轨迹推断其位置，预测机制可能会有效地减少与这些物体相关的处理时间。在这里，我们使用源自似动范式的脑电图 (EEG) 数据的时间分辨解码来证明两种独立的预测机制的相互作用。首先，我们揭示了在似动序列中的第二个物体出现时，即使刺激不包含任何物理运动能量，位置表示也具有预测潜伏期优势。这与存在全向、层内亚阈值活动波一致，这些波使编码相邻位置的神经元更接近其发射阈值，从而减少其中一个位置中第二个刺激的处理时间。其次，我们表明，一旦似动刺激的方向被唯一确定，从第三个序列位置开始，就会出现额外的方向特异性潜伏期优势。由于早期视觉区域的感受野太小，无法包含连续的似动位置（正如第二个刺激位置的潜伏期调制缺乏所证明的那样），因此这种潜伏期优势很可能是由于来自更高视觉区域的下行预测通过反馈连接到较低的视觉区域。最后，我们揭示出，当物体的轨迹意外反转时，需要克服促进物体在预期位置处理的相同预测激活，从而导致违反预测的刺激出现额外的潜伏期劣势。总的来说，我们的结果表明，两种互补的机制相互作用，形成和修正视觉运动处理中的预测，调节不同视觉处理水平的神经位置表示的潜伏期。
