Department of Neurology and Stroke and Hertie Institute for Clinical Brain Research, Eberhard-Karls University of Tübingen, 72076 Tübingen, Germany.
Department of Neurology and Stroke and Hertie Institute for Clinical Brain Research, Eberhard-Karls University of Tübingen, 72076 Tübingen, Germany
J Neurosci. 2018 Dec 5;38(49):10525-10534. doi: 10.1523/JNEUROSCI.1470-18.2018. Epub 2018 Oct 24.
The theory of communication through coherence predicts that effective connectivity between nodes in a distributed oscillating neuronal network depends on their instantaneous excitability state and phase synchronicity (Fries, 2005). Here, we tested this prediction by using state-dependent millisecond-resolved real-time electroencephalography-triggered dual-coil transcranial magnetic stimulation (EEG-TMS) (Zrenner et al., 2018) to target the EEG-negative (high-excitability state) versus EEG-positive peak (low-excitability state) of the sensorimotor μ-rhythm in the left (conditioning) and right (test) motor cortex (M1) of 16 healthy human subjects (9 female, 7 male). Effective connectivity was tested by short-interval interhemispheric inhibition (SIHI); that is, the inhibitory effect of the conditioning TMS pulse given 10-12 ms before the test pulse on the test motor-evoked potential. We compared the four possible combinations of excitability states (negative peak, positive peak) and phase relations (in-phase, out-of-phase) of the μ-rhythm in the conditioning and test M1 and a random phase condition. Strongest SIHI was found when the two M1 were in phase for the high-excitability state (negative peak of the μ-rhythm), whereas the weakest SIHI occurred when they were out of phase and the conditioning M1 was in the low-excitability state (positive peak). Phase synchronicity contributed significantly to SIHI variation, with stronger SIHI in the in-phase than out-of-phase conditions. These findings are in exact accord with the predictions of the theory of communication through coherence. They open a translational route for highly effective modification of brain connections by repetitive stimulation at instants in time when nodes in the network are phase synchronized and excitable. The theory of communication through coherence predicts that effective connectivity between nodes in distributed oscillating brain networks depends on their instantaneous excitability and phase relation. We tested this hypothesis in healthy human subjects by real-time analysis of brain states by electroencephalography in combination with transcranial magnetic stimulation of left and right motor cortex. We found that short-interval interhemispheric inhibition, a marker of interhemispheric effective connectivity, was maximally expressed when the two motor cortices were in phase for a high-excitability state (the trough of the sensorimotor μ-rhythm). We conclude that findings are consistent with the theory of communication through coherence. They open a translational route to highly effectively modify brain connections by repetitive stimulation at instants in time of phase-synchronized high-excitability states.
通过相干性进行交流的理论预测，分布振荡神经元网络中节点之间的有效连接取决于它们的瞬时兴奋性状态和相位同步性（Fries，2005）。在这里，我们通过使用状态相关的毫秒分辨率实时脑电图触发双线圈经颅磁刺激（EEG-TMS）（Zrenner 等人，2018）来测试这一预测，该方法针对左侧（条件）和右侧（测试）运动皮层（M1）的感觉运动μ节律的 EEG 负峰（高兴奋性状态）与 EEG 正峰（低兴奋性状态）（Zrenner 等人，2018）。通过短间隔半球间抑制（SIHI）测试有效连接；即，在测试脉冲之前 10-12 毫秒给予的条件 TMS 脉冲对测试运动诱发电位的抑制作用。我们比较了条件和测试 M1 以及随机相位条件下 μ 节律的兴奋性状态（负峰，正峰）和相位关系（同相，异相）的四种可能组合。当两个 M1 处于高兴奋性状态（μ 节律的负峰）时，它们同相时的 SIHI 最强，而当它们异相且条件 M1 处于低兴奋性状态（μ 节律的正峰）时，SIHI 最弱。相位同步对 SIHI 变化有重要贡献，同相条件下的 SIHI 比异相条件强。这些发现与通过相干性进行交流的理论的预测完全一致。它们为通过在网络节点相位同步和可兴奋的时刻重复刺激来高度有效地修饰大脑连接开辟了一条转化途径。通过相干性进行交流的理论预测，分布振荡脑网络中节点之间的有效连接取决于它们的瞬时兴奋性和相位关系。我们通过实时分析脑电图结合经颅磁刺激左、右运动皮层来测试健康人体受试者的这一假设。我们发现，短间隔半球间抑制，即半球间有效连接的标志物，在两个运动皮层在高兴奋性状态（感觉运动μ 节律的波谷）同相时表达最大。我们得出的结论是，这些发现与通过相干性进行交流的理论是一致的。它们为通过在相位同步的高兴奋性状态下的时间点进行重复刺激来高度有效地修饰大脑连接开辟了一条转化途径。
