Superior Intraparietal Sulcus Controls the Variability of Visual Working Memory Precision
Superior Intraparietal Sulcus Controls the Variability of Visual Working Memory Precision
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DOI：
10.1523/jneurosci.1596-15.2016
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发表时间：
2016-05
期刊：
影响因子：
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通讯作者：
E. G. Galeano Weber;B. Peters;T. Hahn;C. Bledowski;C. Fiebach
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文献类型：
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作者：
E. G. Galeano Weber;B. Peters;T. Hahn;C. Bledowski;C. Fiebach
工作记忆 (WM) 容量的限制在很大程度上取决于可用于将 WM 内容维持在激活状态的认知资源。事实证明，增加 WM 中要维护的项目数量会降低 WM 的精度，并增加 WM 精度随时间的变化。尽管 WM 精度最近与神经代码（尤其是早期感觉皮层中的神经代码）相关，但迄今为止，我们还不了解 WM 精度变异性背后的神经基础，以及如何在高负载下保持 WM 精度。为了填补这一空白，我们将人类功能磁共振成像与延迟颜色估计 WM 任务中的行为表现计算模型相结合。行为结果复制了高负载（5 > 3 > 1 种颜色）下 WM 精度的降低和精度变异性的增加。在样本开始后 2-4 秒的 WM 任务中测量初级视觉皮层 (V1) 和上顶内沟 (IPS) 中的负载依赖性 BOLD 信号，并通过 WM 精度变异性中与负载相关的变化的个体差异进行调节。尽管卓越 IPS 中更强的负载相关 BOLD 增加与精度变异性的较低增加相关，从而稳定了 WM 性能，但 V1 却观察到了相反的情况。最后，负载对行为精度和精度变异性的不利影响伴随着与负载相关的左上 IPS 解码记忆刺激（颜色）准确性的下降。我们认为，卓越的 IPS 可以通过减少面对更高负载时内存精度的变化来稳定视觉 WM 性能。意义声明本研究通过将功能磁共振成像与人类参与者行为表现的认知模型相结合，研究了视觉工作记忆能力限制的神经基础。它提供的证据表明，顶内沟（IPS）是一个关键的大脑区域，在记忆负荷增加的情况下影响个体之间和个体内部视觉工作记忆精度的变异性（Fougnie et al., 2012; van den Berg et al., 2012），可能与枕叶皮层的感知系统配合。这些发现极大地扩展了我们对视觉工作记忆容量限制及其神经基础的本质的理解。我们的工作强调了在功能磁共振成像研究中将认知模型与单变量和多变量方法相结合的重要性，从而提高我们对大脑行为关系的了解。
Limitations of working memory (WM) capacity depend strongly on the cognitive resources that are available for maintaining WM contents in an activated state. Increasing the number of items to be maintained in WM was shown to reduce the precision of WM and to increase the variability of WM precision over time. Although WM precision was recently associated with neural codes particularly in early sensory cortex, we have so far no understanding of the neural bases underlying the variability of WM precision, and how WM precision is preserved under high load. To fill this gap, we combined human fMRI with computational modeling of behavioral performance in a delayed color-estimation WM task. Behavioral results replicate a reduction of WM precision and an increase of precision variability under high loads (5 > 3 > 1 colors). Load-dependent BOLD signals in primary visual cortex (V1) and superior intraparietal sulcus (IPS), measured during the WM task at 2–4 s after sample onset, were modulated by individual differences in load-related changes in the variability of WM precision. Although stronger load-related BOLD increase in superior IPS was related to lower increases in precision variability, thus stabilizing WM performance, the reverse was observed for V1. Finally, the detrimental effect of load on behavioral precision and precision variability was accompanied by a load-related decline in the accuracy of decoding the memory stimuli (colors) from left superior IPS. We suggest that the superior IPS may contribute to stabilizing visual WM performance by reducing the variability of memory precision in the face of higher load. SIGNIFICANCE STATEMENT This study investigates the neural bases of capacity limitations in visual working memory by combining fMRI with cognitive modeling of behavioral performance, in human participants. It provides evidence that the superior intraparietal sulcus (IPS) is a critical brain region that influences the variability of visual working memory precision between and within individuals (Fougnie et al., 2012; van den Berg et al., 2012) under increased memory load, possibly in cooperation with perceptual systems of the occipital cortex. These findings substantially extend our understanding of the nature of capacity limitations in visual working memory and their neural bases. Our work underlines the importance of integrating cognitive modeling with univariate and multivariate methods in fMRI research, thus improving our knowledge of brain-behavior relationships.