Department of Psychology, University of Cambridge, Cambridge, United Kingdom.
PLoS Comput Biol. 2019 Feb 21;15(2):e1006563. doi: 10.1371/journal.pcbi.1006563. eCollection 2019 Feb.
Visuospatial working memory enables us to maintain access to visual information for processing even when a stimulus is no longer present, due to occlusion, our own movements, or transience of the stimulus. Here we show that, when localizing remembered stimuli, the precision of spatial recall does not rely solely on memory for individual stimuli, but additionally depends on the relative distances between stimuli and visual landmarks in the surroundings. Across three separate experiments, we consistently observed a spatially selective improvement in the precision of recall for items located near a persistent landmark. While the results did not require that the landmark be visible throughout the memory delay period, it was essential that it was visible both during encoding and response. We present a simple model that can accurately capture human performance by considering relative (allocentric) spatial information as an independent localization estimate which degrades with distance and is optimally integrated with egocentric spatial information. Critically, allocentric information was encoded without cost to egocentric estimation, demonstrating independent storage of the two sources of information. Finally, when egocentric and allocentric estimates were put in conflict, the model successfully predicted the resulting localization errors. We suggest that the relative distance between stimuli represents an additional, independent spatial cue for memory recall. This cue information is likely to be critical for spatial localization in natural settings which contain an abundance of visual landmarks.
视空间工作记忆使我们能够在刺激不再存在（由于遮挡、我们自己的运动或刺激的短暂性）的情况下，保持对视觉信息的处理访问。在这里，我们表明，在定位记忆中的刺激时，空间回忆的精度不仅依赖于对单个刺激的记忆，还依赖于刺激与周围视觉地标之间的相对距离。在三个独立的实验中，我们一致观察到，在靠近持久地标定位的项目的回忆精度上出现了空间选择性的提高。虽然结果并不要求地标在整个记忆延迟期间都可见，但它在编码和响应期间都可见是至关重要的。我们提出了一个简单的模型，可以通过考虑相对（无参照）空间信息作为独立的定位估计来准确地捕捉人类的表现，该估计会随距离而退化，并与自我中心空间信息最佳地整合。关键是，无参照信息的编码不会影响自我中心估计，这表明两种信息来源可以独立存储。最后，当自我中心和无参照估计发生冲突时，该模型成功地预测了由此产生的定位误差。我们认为，刺激之间的相对距离代表了记忆回忆的另一个独立的空间线索。这种线索信息对于包含大量视觉地标自然环境中的空间定位可能是至关重要的。
