虽然我们能够在工作视觉记忆中记住几个不同目标，但我们是怎样记住每个目标的特定细节及视觉特征的仍是一个谜。对工作记忆负责的高级区域中的神经元 似乎对视觉细节并没有选择性，大脑皮层的早期视觉区域具有能够处理来自眼睛的输入视觉信号的独特能力，但过去人们认为它不能执行如记忆等高级认知功能。
Stephanie Harrison 和 Frank Tong等人，利用对来自功能性核磁共振成像(fMRI)的数据进行解码的一种新方法，发现早期视觉区域能够保持关于存放在工作记忆中的相关特征的特定信 息。研究人员向志愿者出示了两个不同取向的条纹图案，要他们在被fMRI扫描时记住其中一个取向。从对扫描结果所做的分析，研究人员有可能预测，在两个取 向的图案中的哪一个中，一个目标在超过80%的测试中都会被保留。
生物谷推荐原始出处：
Nature 458, 632-635 (2 April 2009) | doi:10.1038/nature07832
Decoding reveals the contents of visual working memory in early visual areas
Stephenie A. Harrison1 & Frank Tong1
Psychology Department and Vanderbilt Vision Research Center, Vanderbilt University, Nashville, Tennessee 37240, USA
Visual working memory provides an essential link between perception and higher cognitive functions, allowing for the active maintenance of information about stimuli no longer in view1, 2. Research suggests that sustained activity in higher-order prefrontal, parietal, inferotemporal and lateral occipital areas supports visual maintenance3, 4, 5, 6, 7, 8, 9, 10, 11, and may account for the limited capacity of working memory to hold up to 3–4 items9, 10, 11. 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 seconds12. One proposal is that sensory areas serve to maintain fine-tuned feature information13, but early visual areas show little to no sustained activity over prolonged delays14, 15, 16. 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. Using functional magnetic resonance imaging and pattern classification methods, we found that activity patterns in visual areas V1–V4 could predict which of two oriented gratings was held in memory with mean accuracy levels upwards of 80%, even in participants whose activity 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.
source: 生物谷
