Fonctions Cérébrales et Neuromodulation, Grenoble Institut des Neurosciences, Université Joseph Fourier, Grenoble, France.
Fonctions Cérébrales et Neuromodulation, Grenoble Institut des Neurosciences, Université Joseph Fourier, Grenoble, France; Clinique Universitaire de Psychiatrie, Pôle Psychiatrie Neurologie, Centre Hospitalier Universitaire, Grenoble, France.
Neuroimage. 2014 Mar;88:91-9. doi: 10.1016/j.neuroimage.2013.11.029. Epub 2013 Nov 21.
Repetitive transcranial magnetic stimulation (rTMS) modulates brain activity in different ways according to the stimulation parameters. Although the after-effects of rTMS over motor cortex are well documented in healthy individuals, less is known about the stimulation of dorso-lateral prefrontal cortex (DLPFC). Here, we studied in 20 healthy subjects how cortical oscillations are modulated by four different active rTMS protocols (1Hz, 10Hz, continuous and intermittent theta bursts - cTBS and iTBS) of the left DLPFC, and by a sham protocol used as a control condition, by comparing the spectral power of pre- and post-rTMS electroencephalographic (EEG) recordings of 15min duration. EEG spectrum was estimated with the fast Fourier transform (FFT) and partitioned using the common physiological frequency bands: delta (1-4Hz), theta (3.5-7Hz), alpha (7.5-13Hz), low beta (14-22Hz), high beta (22-30Hz) and gamma (30-45Hz). Statistical analyses of EEG changes induced by rTMS were computed with Statistical Parametric Mapping (SPM) for EEG, in every frequency band, at the scalp level and at the cortex level. We found for every active protocol a significant decrease of delta and theta power on left prefrontal electrodes, mainly localised in the left DLPFC. In higher frequency bands (beta and gamma), the decrease of power in the DLPFC was also observed contralaterally. Protocol-specific amplitude effects were found in the prefrontal cortex bilaterally in all frequency bands, but also in parietal and temporal regions in low EEG frequencies. In high frequencies, EEG power in the prefrontal cortex increased after rTMS for 10Hz and iTBS protocols, but this effect did not survive the comparison to Sham responses. Because large delta and theta activity is usually associated with cortical inhibition, observed rTMS-induced EEG changes in low frequencies suggest that rTMS of DLPFC transiently decreases local cortical inhibition. Importantly, local responses take place in association with other unknown mechanisms that modulate inter-hemispheric connectivity between homologous regions, resulting in the increase or decrease of fast activity in each prefrontal lobe, depending on the stimulation protocol. Only decreases of fast activity following active rTMS could be detected as significant when compared to Sham stimulation.
重复经颅磁刺激（rTMS）根据刺激参数以不同的方式调节大脑活动。尽管在健康个体中已经很好地记录了 rTMS 对运动皮层的后效，但对于背外侧前额叶皮层（DLPFC）的刺激知之甚少。在这里，我们研究了 20 名健康受试者，研究了左 DLPFC 的四种不同的主动 rTMS 方案（1Hz、10Hz、连续和间歇性 theta 爆发-cTBS 和 iTBS）以及作为对照条件的假刺激方案如何调节皮质振荡，通过比较 15 分钟时长的 rTMS 前后脑电图（EEG）记录的频谱功率。使用快速傅里叶变换（FFT）估计 EEG 频谱，并使用常见的生理频带进行分区：δ（1-4Hz）、θ（3.5-7Hz）、α（7.5-13Hz）、低β（14-22Hz）、高β（22-30Hz）和γ（30-45Hz）。在头皮水平和皮层水平上，使用基于 EEG 的统计参数映射（SPM）对 rTMS 引起的 EEG 变化进行了统计分析。我们发现，对于每个主动方案，在左前额电极上都会观察到 delta 和 theta 功率显著降低，主要位于左 DLPFC。在较高的频带（β和γ）中，也观察到对侧 DLPFC 的功率降低。在所有频带中，双侧前额叶皮质都发现了与方案特异性相关的振幅效应，但在低频 EEG 中也发现了顶叶和颞叶区域。在高频下，10Hz 和 iTBS 方案的 rTMS 后，前额叶皮层的 EEG 功率增加，但与 Sham 反应相比，这种效应并未持续。因为大的 delta 和 theta 活动通常与皮质抑制有关，所以在低频观察到的 rTMS 诱导的 EEG 变化表明 DLPFC 的 rTMS 短暂地降低了局部皮质抑制。重要的是，局部反应与调节同源区域之间的半球间连通性的其他未知机制有关，导致每个前额叶叶快速活动的增加或减少，这取决于刺激方案。与 Sham 刺激相比，只有主动 rTMS 后快速活动的减少才能被检测为显著。
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