Department of Psychology, New York University, New York, United States.
NYU Abu Dhabi Institute, Abu Dhabi, United Arab Emirates.
Elife. 2020 Sep 1;9:e56603. doi: 10.7554/eLife.56603.
Perception depends on a complex interplay between feedforward and recurrent processing. Yet, while the former has been extensively characterized, the computational organization of the latter remains largely unknown. Here, we use magneto-encephalography to localize, track and decode the feedforward and recurrent processes of reading, as elicited by letters and digits whose level of ambiguity was parametrically manipulated. We first confirm that a feedforward response propagates through the ventral and dorsal pathways within the first 200 ms. The subsequent activity is distributed across temporal, parietal and prefrontal cortices, which sequentially generate five levels of representations culminating in action-specific motor signals. Our decoding analyses reveal that both the content and the timing of these brain responses are best explained by a hierarchy of recurrent neural assemblies, which both maintain and broadcast increasingly rich representations. Together, these results show how recurrent processes generate, over extended time periods, a cascade of decisions that ultimately accounts for subjects' perceptual reports and reaction times.
知觉取决于前馈和递归处理之间的复杂相互作用。然而，尽管前者已经得到了广泛的描述，但后者的计算组织在很大程度上仍然未知。在这里，我们使用脑磁图来定位、跟踪和解码阅读的前馈和递归过程，这些过程是由参数化操纵的字母和数字激发的。我们首先证实，前馈响应在最初的 200 毫秒内通过腹侧和背侧通路传播。随后的活动分布在颞叶、顶叶和前额叶皮层，这些皮层依次产生五个层次的代表，最终产生特定于动作的运动信号。我们的解码分析表明，这些大脑反应的内容和时间都最好用递归神经网络集合的层次结构来解释，该层次结构既保持又广播越来越丰富的表示。总之，这些结果表明，递归过程如何在较长时间内产生一连串的决策，最终解释了受试者的知觉报告和反应时间。
