Pratte Michael S, Tong Frank
Psychology Department and Vanderbilt Vision Research Center, Vanderbilt University, Nashville, TN, USA.
J Vis. 2014 Mar 19;14(3):22. doi: 10.1167/14.3.22.
Recent fMRI decoding studies have demonstrated that early retinotopic visual areas exhibit similar patterns of activity during the perception of a stimulus and during the maintenance of that stimulus in working memory. These findings provide support for the sensory recruitment hypothesis that the mechanisms underlying perception serve as a foundation for visual working memory. However, a recent study by Ester, Serences, and Awh (2009) found that the orientation of a peripheral grating maintained in working memory could be classified from both the contralateral and ipsilateral regions of the primary visual cortex (V1), implying that, unlike perception, feature-specific information was maintained in a nonretinotopic manner. Here, we evaluated the hypothesis that early visual areas can maintain information in a spatially specific manner and will do so if the task encourages the binding of feature information to a specific location. To encourage reliance on spatially specific memory, our experiment required observers to retain the orientations of two laterally presented gratings. Multivariate pattern analysis revealed that the orientation of each remembered grating was classified more accurately based on activity patterns in the contralateral than in the ipsilateral regions of V1 and V2. In contrast, higher extrastriate areas exhibited similar levels of performance across the two hemispheres. A time-resolved analysis further indicated that the retinotopic specificity of the working memory representation in V1 and V2 was maintained throughout the retention interval. Our results suggest that early visual areas provide a cortical basis for actively maintaining information about the features and locations of stimuli in visual working memory.
最近的功能磁共振成像解码研究表明，早期视网膜拓扑视觉区域在刺激感知过程和工作记忆中对该刺激的维持过程中表现出相似的活动模式。这些发现为感觉募集假说提供了支持，即感知背后的机制为视觉工作记忆奠定了基础。然而，埃斯特、塞伦斯和阿夫（2009年）最近的一项研究发现，工作记忆中维持的外周光栅的方向可以从初级视觉皮层（V1）的对侧和同侧区域进行分类，这意味着与感知不同，特征特异性信息是以非视网膜拓扑方式维持的。在这里，我们评估了这样一个假说，即早期视觉区域可以以空间特异性方式维持信息，如果任务鼓励将特征信息与特定位置绑定，它们就会这样做。为了鼓励依赖空间特异性记忆，我们的实验要求观察者记住两个横向呈现的光栅的方向。多变量模式分析显示，根据V1和V2对侧区域的活动模式，每个记忆光栅的方向比同侧区域分类得更准确。相比之下，更高层次的纹外区域在两个半球表现出相似的性能水平。时间分辨分析进一步表明，V1和V2中工作记忆表征的视网膜拓扑特异性在整个保持间隔内都得以维持。我们的结果表明，早期视觉区域为在视觉工作记忆中积极维持有关刺激特征和位置的信息提供了皮层基础。
