Cross-frequency coupling supports multi-item working memory in the human hippocampus
Cross-frequency coupling supports multi-item working memory in the human hippocampus
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DOI：
10.1073/pnas.0911531107
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发表时间：
2010-02-16
影响因子：
11.1
通讯作者：
Fell, Juergen
中科院分区：
文献类型：
--
作者：
Axmacher, Nikolai;Henseler, Melanie M.;Fell, Juergen
最近的研究表明，海马体不仅支持长时记忆编码，而且在多个项目的工作记忆(WM)维持中发挥作用；然而，多项目维持的神经机制尚不清楚。理论研究表明，在伽马频率范围(25-100赫兹)内同步的神经组件维持着多个项目，这些神经组件被锁定在西塔频率范围(4-8赫兹)内振荡活动的连续相位范围。事实上，高频活动的幅度与较慢的振荡阶段的交叉频率耦合在动物和人类中都有描述，但从未与认知过程的理论模型联系起来。在这里，我们使用人类癫痫患者的颅内脑电记录来测试来自理论工作的关键预测。首先，我们证明了在WM中同时维持多个项目伴随着海马区振荡活动的交叉频率耦合，这是在多项目WM中招募的。其次，维持越来越多的项目与调制β/伽马幅度和较低频率的theta带活动有关，这与伽马周期增加表征数量需要更长周期的想法一致。这种效应不能用θ或β/伽马能量的不同来解释。第三，我们描述了交叉频率耦合的精度如何预测单个WM的性能。这些数据支持这样一种观点，即人类的工作记忆依赖于使用相位信息的神经编码。
Recent findings indicate that the hippocampus supports not only long-term memory encoding but also plays a role in working memory (WM) maintenance of multiple items; however, the neural mechanism underlying multi-item maintenance is still unclear. Theoretical work suggests that multiple items are being maintained by neural assemblies synchronized in the gamma frequency range(25-100 Hz) that are locked to consecutive phase ranges of oscillatory activity in the theta frequency range (4-8 Hz). Indeed, cross-frequency coupling of the amplitude of high-frequency activity to the phase of slower oscillations has been described both in animals and in humans, but has never been linked to a theoretical model of a cognitive process. Here we used intracranial EEG recordings in human epilepsy patients to test pivotal predictions from theoretical work. First, we show that simultaneous maintenance of multiple items in WM is accompanied by cross-frequency coupling of oscillatory activity in the hippocampus, which is recruited during multi-item WM. Second, maintenance of an increasing number of items is associated with modulation of beta/gamma amplitude with theta band activity of lower frequency, consistent with the idea that longer cycles are required for an increased number of representations by gamma cycles. This effect cannot be explained by a difference in theta or beta/gamma power. Third, we describe how the precision of cross-frequency coupling predicts individual WM performance. These data support the idea that working memory in humans depends on a neural code using phase information.