Cortical capacity constraints for visual working memory: dissociation of fMRI load effects in a fronto-parietal network
Cortical capacity constraints for visual working memory: dissociation of fMRI load effects in a fronto-parietal network
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DOI：
10.1016/j.neuroimage.2003.07.021
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发表时间：
2003-11-01
期刊：
影响因子：
5.7
通讯作者：
Munk, MHJ
中科院分区：
文献类型：
--
作者：
Linden, DEJ;Bittner, RA;Munk, MHJ
工作记忆（WM）容量的限制和它们的神经生理学相关的理解高级认知功能的特殊相关性。来自行为研究的证据表明，有限的注意力资源有助于这些能力的限制。在一项与事件相关的功能性磁共振成像（fMRI）研究中，我们探讨了人类视觉WM系统的能力，多达四个复杂的非自然物体使用延迟的歧视任务。在整个任务过程中，当记忆中必须保持一个以上的对象时，双侧前额叶和顶叶区域的血氧水平依赖性活动相对于基线增加。在背外侧前额叶皮层（DLPFC）和前辅助运动区（pre-SMA）观察到对记忆负荷反应的单调增加。相反，活动在额眼领域（FEF）和区域沿着顶内沟（IPS）达到高峰时，受试者必须保持只有两个或三个对象，并在最高负荷条件下下降。记忆负荷对皮质活动的影响的这种分离表明，IPS和FEF所支持的认知操作（最有可能与注意力相关）在接近容量限制时无法支持视觉WM。大脑活动与性能的相关性意味着，只有DLPFC和pre-SMA，支持视觉信息的综合表示进行的操作，帮助受试者保持在最高负荷条件下的性能的合理水平。这些结果表明，至少有两个不同的皮质子系统招募视觉WM，它们之间的相互作用的变化时，达到的容量限制。(C)2003年爱思唯尔公司All rights reserved.
Working memory (WM) capacity limitations and their neurophysiological correlates are of special relevance for the understanding of higher cognitive functions. Evidence from behavioral studies suggests that restricted attentional resources contribute to these capacity limitations. In an event-related functional magnetic resonance imaging (fMRI) study, we probed the capacity of the human visual WM system for up to four complex nonnatural objects using a delayed discrimination task. A number of prefrontal and parietal areas bilaterally showed increased blood oxygen level-dependent activity, relative to baseline, throughout the task when more than one object had to be held in memory. Monotonic increases in response to memory load were observed bilaterally in the dorsolateral prefrontal cortex (DLPFC) and the presupplementary motor area (pre-SMA). Conversely, activity in the frontal eye fields (FEFs) and in areas along the intraparietal sulcus (IPS) peaked when subjects had to maintain only two or three objects and decreased in the highest load condition. This dissociation of memory load effects on cortical activity suggests that the cognitive operations subserved by the IPS and FEF, which are most likely related to attention, fail to support visual WM when the capacity limit is approached. The correlation of brain activity with performance implies that only the operations performed by the DLPFC and pre-SMA, which support an integrated representation of visual information, helped subjects to maintain a reasonable level of performance in the highest load condition. These results indicate that at least two distinct cortical subsystems are recruited for visual WM, and that their interplay changes when the capacity limit is reached. (C) 2003 Elsevier Inc. All rights reserved.