Axmacher Nikolai, Mormann Florian, Fernández Guillén, Cohen Michael X, Elger Christian E, Fell Juergen
Department of Epileptology, University of Bonn, 53105 Bonn, Germany.
J Neurosci. 2007 Jul 18;27(29):7807-16. doi: 10.1523/JNEUROSCI.0962-07.2007.
In contrast to classical findings that the medial temporal lobe (MTL) specifically underlies long-term memory, previous data suggest that MTL structures may also contribute to working memory (WM). However, the neural mechanisms by which the MTL supports WM have remained unknown. Here, we exploit intracranial EEG to identify WM-specific sustained activity patterns with the highest temporal and spatial resolution currently available in humans. Using a serial Sternberg paradigm, we found a positive shift of the direct current (DC) potential and a long-lasting decrease in MTL gamma-band activity during maintenance of a single item, reflective of a sustained reduction in neural activity. Maintenance of an increasing number of items elicited an incrementally negative shift of the DC potential and an increase in MTL gamma-band activity. In addition, the paradigm was conducted in healthy control subjects using functional magnetic resonance imaging. This confirmed that our results were not caused by pathological processes within the MTL, and that this region was indeed specifically activated during the task. Our results thus provide direct evidence for sustained neural activity patterns during working memory maintenance in the MTL, and show that these patterns depend on WM load.
与内侧颞叶（MTL）专门支持长期记忆的经典研究结果相反，先前的数据表明MTL结构也可能有助于工作记忆（WM）。然而，MTL支持WM的神经机制仍然未知。在这里，我们利用颅内脑电图来识别具有目前人类可用的最高时间和空间分辨率的WM特异性持续活动模式。使用串行斯特恩伯格范式，我们发现，在单个项目的维持期间，直流（DC）电位出现正向偏移，MTLγ波段活动持续下降，这反映了神经活动的持续减少。维持数量不断增加的项目会引起DC电位逐渐负向偏移以及MTLγ波段活动增加。此外，该范式在健康对照受试者中使用功能磁共振成像进行。这证实了我们的结果不是由MTL内的病理过程引起的，并且该区域在任务期间确实被特异性激活。因此，我们的结果为MTL在工作记忆维持期间的持续神经活动模式提供了直接证据，并表明这些模式取决于WM负荷。
