Gamma amplitudes are coupled to theta phase in human EEG during visual perception
Gamma amplitudes are coupled to theta phase in human EEG during visual perception
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DOI：
10.1016/j.ijpsycho.2006.07.005
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发表时间：
2007-04-01
影响因子：
3
通讯作者：
Herrmann, Christoph S.
中科院分区：
文献类型：
--
作者：
Demiralp, Tamer;Bayraktaroglu, Zubeyir;Herrmann, Christoph S.
人类受试者通常会在短期记忆（STM）中保留大约7个项目（正负两个）。已经提出了一个理论神经元模型来解释这一现象，该模型使用大脑在伽马和θ频率范围内振荡的生理参数，即分别约为30-80和4-8 Hz。在该模型中，STM容量等于伽马周期的数量（例如，40赫兹25毫秒），它适合一个θ周期（例如，6赫兹166毫秒）。该模型基于两个假设：(1)θ活动应该调节γ活动；(2) θ / γ比值应与人类STM能力相关。第一个假设得到了电生理学数据的支持，这些数据显示伽马振荡的振幅是由θ活动的相位调制的。然而，到目前为止，这只证明了颅内记录。我们分析了13名受试者感知已知和未知视觉刺激的记忆实验中记录的人类事件相关脑电图振荡。该范式揭示了伽马范围内与事件相关的振荡，这在很大程度上取决于同时发生的θ活动的相位。我们的数据是第一个头皮记录的人类脑电图记录，揭示了伽马振幅和θ振荡相位之间的关系，支持上述理论的第一个假设。有趣的是，所涉及的频率显示出7:1的比例。然而，这个比率并不一定决定人类的STM能力。由于这种相关性在我们的范式中没有得到明确的检验，我们的数据对第二个假设并不是结论性的。同样可以想象的是，在与更远的大脑区域相互作用之前，局部伽马活动需要被下采样到θ活动，而不是θ相位调制伽马振幅。(c) 2006 Elsevier B.V.版权所有
Human subjects typically keep about seven items (plus or minus two) in short-term memory (STM). A theoretical neuronal model has been proposed to explain this phenomenon with physiological parameters of brain oscillations in the gamma and theta frequency range, i.e., roughly 30-80 and 4-8 Hz, respectively. In that model, STM capacity equals the number of gamma cycles (e.g., 25 ms for 40 Hz), which fit into one theta cycle (e.g., 166 ms for 6 Hz). The model is based on two assumptions: (1) theta activity should modulate gamma activity; and (2) the theta/gamma ratio should correlate with human STM capacity. The first assumption is supported by electrophysiological data showing that the amplitude of gamma oscillations is modulated by the phase of theta activity. However, so far, this has only been demonstrated for intracranial recordings. We analyzed human event-related EEG oscillations recorded in a memory experiment in which 13 subjects perceived known and unknown visual stimuli. The paradigm revealed event-related oscillations in the gamma range, which depended significantly on the phase of simultaneous theta activity. Our data are the first scalp-recorded human EEG recordings revealing a relationship between the gamma amplitude and the phase of theta oscillations, supporting the first assumption of the above-mentioned theory. Interestingly, the involved frequencies revealed a 7:1 ratio. However, this ratio does not necessarily determine human STM capacity. Since such a correlation was not explicitly tested in our paradigm, our data are not conclusive about the second assumption. Instead of theta phase modulating gamma amplitude, it is also conceivable that focal gamma activity needs to be downsampled to theta activity, before it can interact with more distant brain regions. (c) 2006 Elsevier B.V. All rights reserved.