Theta-gamma phase-phase coupling during working memory maintenance in the human hippocampus
Theta-gamma phase-phase coupling during working memory maintenance in the human hippocampus
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DOI：
10.1080/17588928.2015.1058254
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发表时间：
2015-10-02
影响因子：
2
通讯作者：
Fell, Juergen
中科院分区：
文献类型：
--
作者：
Chaieb, Leila;Leszczynski, Marcin;Fell, Juergen
theta-gamma神经编码理论认为，多个项目在工作记忆（WM）中通过叠加在theta振荡上的伽马周期来表示。为了实现多个项目的稳定、非干扰表示，这样的θ-伽马神经代码可以通过相位-相位耦合来反映，即，伽马子周期精确锁定到特定的θ相位。最近的数据表明，海马体对多项目工作记忆有重要贡献。因此，我们研究了基于颅内EEG记录的术前癫痫患者进行系列斯滕贝格WM任务的变体的海马中的相位-相位耦合模式。根据theta-gamma编码理论的预测，我们观察到在工作记忆维持期间，与试验间隔相比，theta-gamma和beta/gamma活动之间的相位-相位耦合增加。这些相-相耦合模式是明显的，在维护过程中的两个和四个项目，但不是在维护过程中的一个单一的项目，其中显着的低耦合比发生。此外，我们观察到，负载依赖性变化的耦合因子与个人WM能力。我们的数据表明，多项目WM与海马相位之间的θ和β/γ活性耦合的变化。
The theta-gamma neural coding theory suggests that multiple items are represented in working memory (WM) by a superposition of gamma cycles on theta oscillations. To enable a stable, non-interfering representation of multiple items, such a theta-gamma neural code may be reflected by phase-phase coupling, i.e., a precise locking of gamma subcycles to specific theta phases. Recent data have indicated that the hippocampus critically contributes to multi-item working memory. Therefore, we investigated phase-phase coupling patterns in the hippocampus based on intracranial EEG recordings in presurgical epilepsy patients performing a variant of the serial Sternberg WM task. In accordance with predictions of the theta-gamma coding theory, we observed increased phase-phase coupling between theta and beta/gamma activity during working memory maintenance compared to inter-trial intervals. These phase-phase coupling patterns were apparent during maintenance of two and four items, but not during maintenance of a single item, where prominent lower coupling ratios occurred. Furthermore, we observed that load-dependent changes of coupling factors correlated with individual WM capacities. Our data demonstrate that multi-item WM is associated with changes in hippocampal phase-phase coupling between theta and beta/gamma activity.