The posteromedial cortex (PMC) is a major hub of the brain's default mode network, and is implicated in a broad range of internally driven cognitions, including visuospatial working memory. However, its precise contribution to these cognitive processes remains unclear. Using MEG, we measured PMC activity in healthy human participants (young adults of both sexes) while they performed a visuospatial working memory task. Multivariate pattern classification analyses revealed stimulus-related information during encoding and retrieval in a set of a priori defined cortical ROIs, including prefrontal, occipital, and ventrotemporal cortices, in addition to PMC. We measured the extent to which this stimulus information was exchanged between areas in an information flow analysis, measuring Granger-causal relationships between areas over time. Consistent with the visual nature of the task, information from occipital cortex shaped other regions across most epochs. However, the PMC shaped object representations in occipital and prefrontal cortices during visuospatial working memory, influencing occipital cortex during retrieval and PFC across all task epochs. Our findings are consistent with a proposed role for the PMC in the representation of internal content, including remembered information, and in the comparison of external stimuli with remembered material.

SIGNIFICANCE STATEMENT The human brain operates as a collection of highly interconnected regions. Mapping the function of this interconnectivity, as well as the specializations within different regions, is central to understanding the neural processes underlying cognition. The posteromedial cortex (PMC) is a highly connected cortical region, implicated in visuospatial working memory, although its precise contribution remains unclear. We measured the activity of PMC during a visuospatial working memory task, testing how different regions represented the stimuli, and whether these representations were driven by other cortical regions. We found that PMC influenced stimulus information in other regions across all task phases, suggesting that PMC plays a key role in shaping stimulus representations during visuospatial working memory.

后内侧皮层 (PMC) 是大脑默认模式网络的主要枢纽，与广泛的内部驱动认知有关，包括视觉空间工作记忆。然而，它对这些认知过程的确切贡献仍不清楚。使用 MEG，我们测量了健康人类参与者（男女青年）在执行视觉空间工作记忆任务时的 PMC 活动。多变量模式分类分析揭示了在一组先验定义的皮质 ROI 中编码和检索期间与刺激相关的信息，除了 PMC 之外，还包括前额叶、枕叶和腹颞叶皮质。我们在信息流分析中测量了刺激信息在区域之间交换的程度，测量区域之间随时间变化的格兰杰因果关系。与任务的视觉性质一致，来自枕叶皮层的信息在大多数时期塑造了其他区域。然而，PMC 在视觉空间工作记忆过程中塑造了枕叶和前额叶皮层的物体表征，影响检索过程中的枕叶皮层和所有任务时期的 PFC。我们的研究结果与 PMC 在表示内部内容（包括记忆信息）以及将外部刺激与记忆材料进行比较方面的作用一致。

意义陈述人脑作为高度互连区域的集合而运作。绘制这种互连性的功能以及不同区域内的专业化对于理解认知背后的神经过程至关重要。后内侧皮质（PMC）是一个高度连接的皮质区域，与视觉空间工作记忆有关，尽管其确切的贡献仍不清楚。我们测量了视觉空间工作记忆任务期间 PMC 的活动，测试不同区域如何表示刺激，以及这些表示是否由其他皮质区域驱动。我们发现 PMC 影响所有任务阶段其他区域的刺激信息，这表明 PMC 在视觉空间工作记忆期间塑造刺激表征方面发挥着关键作用。