Decoding reveals the contents of visual working memory in early visual areas.
Decoding reveals the contents of visual working memory in early visual areas.
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DOI：
10.1038/nature07832
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发表时间：
2009-04-02
期刊：
影响因子：
64.8
通讯作者：
Tong, Frank
中科院分区：
文献类型：
--
作者：
Harrison, Stephenie A.;Tong, Frank
视觉工作记忆在感知和更高层次的认知功能之间提供了重要联系，使得能够对不再可见的刺激信息进行主动维持。研究表明，高级前额叶、顶叶、颞下回和外侧枕叶区域的持续活动支持视觉维持，并且可能解释了工作记忆最多能容纳3 - 4个项目的有限容量。由于高级区域缺乏早期感觉区域的视觉选择性，观察者如何能够记住特定的视觉特征，比如光栅的精确方向，并且在数秒的延迟过程中性能衰减极小，这一点一直不清楚。一种观点认为感觉区域用于维持精细调整的特征信息，但早期视觉区域在长时间延迟中几乎没有表现出持续活动。通过使用功能性磁共振成像解码方法，我们在此表明，即使活动的总体水平较低，工作记忆中保持的方向也能够从人类视觉皮层的活动模式中解码出来。V1 - V4区域的活动模式能够预测两种定向光栅中的哪一种被保留在记忆中，平均准确率水平高达80%，即使在参与者经过长时间延迟后活动降至基线水平的情况下也是如此。这些方向选择性活动模式在整个延迟期间持续存在，在单个视觉区域中明显，并且与未被注意的、与任务无关的光栅所引发的反应相似。我们的研究结果表明，在没有物理刺激存在的情况下，早期视觉区域能够在数秒的时间内保留关于视觉工作记忆中所保持的视觉特征的特定信息。
Visual working memory provides an essential link between perception and higher cognitive functions, allowing for the active maintenance of information regarding stimuli no longer in view. Research suggests that sustained activity in higher-order prefrontal, parietal, inferotemporal and lateral occipital areas supports visual maintenance, and may account for working memory’s limited capacity to hold up to 3-4 items. Because higher-order areas lack the visual selectivity of early sensory areas, it has remained unclear how observers can remember specific visual features, such as the precise orientation of a grating, with minimal decay in performance over delays of many seconds. One proposal is that sensory areas serve to maintain fine-tuned feature information, but early visual areas show little to no sustained activity over prolonged delays. Using fMRI decoding methods, here we show that orientations held in working memory can be decoded from activity patterns in the human visual cortex, even when overall levels of activity are low. Activity patterns in areas V1-V4 could predict which of two oriented gratings was held in memory with mean accuracy levels upwards of 80%, even in participants exhibiting activity that fell to baseline levels after a prolonged delay. These orientation-selective activity patterns were sustained throughout the delay period, evident in individual visual areas, and similar to the responses evoked by unattended, task-irrelevant gratings. Our results demonstrate that early visual areas can retain specific information about visual features held in working memory, over periods of many seconds when no physical stimulus is present.
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