背景:皮质兴奋性测量神经对刺激的反应性,通常通过经颅磁刺激(TMS)。兴奋/抑制平衡(E/I)是神经回路的兴奋和抑制活性之间正在进行的平衡。根据一些研究,E/I可以通过脑电图(EEG)信号的建模在体内和非侵入性进行估计,并称为“内在兴奋性”措施。已经提出了几种措施(伽马波段的相位一致性,样本熵,功率谱密度1/f曲线的指数,从趋势波动分析中提取的E/I指数,和阿尔法力量)。初级运动皮层(M1)的间歇性theta爆发刺激(iTBS)是一种非侵入性神经调节技术,可以控制和局灶性增强TMS皮层兴奋性和受刺激半球的E/I。
目的:调查E/I对TMS兴奋性量表的估计程度以及它们之间的关系。
方法:在一组健康受试者的iTBS之前和之后,评估了从静息状态EEG记录中提取的M1兴奋性(TMS)和一些E/I估计值。
结果:TMSM1兴奋性增强,通过运动诱发电位(MEP)测量,皮层在高伽马波段的相位一致性相互关联。E/I的其他指标显示了一些预期的结果,但与TMS兴奋性测量没有相关性或彼此之间有很强的一致性。
结论:EEGE/I估计提供了一个有趣的机会来非侵入地绘制皮质兴奋性图,具有高时空分辨率和与刺激无关的方法。虽然不同的EEGE/I估计可能反映了不同的兴奋-抑制回路的活动,伽玛波段的空间相位同步是最好地捕获初级运动皮层兴奋性变化的量度。
BACKGROUND: Cortical excitability measures neural reactivity to stimuli, usually delivered via Transcranial Magnetic Stimulation (TMS). Excitation/inhibition balance (E/I) is the ongoing equilibrium between excitatory and inhibitory activity of neural circuits. According to some studies, E/I could be estimated in-vivo and non-invasively through the modeling of electroencephalography (EEG) signals and termed \'intrinsic excitability\' measures. Several measures have been proposed (phase consistency in the gamma band, sample entropy, exponent of the power spectral density 1/f curve, E/I index extracted from detrend fluctuation analysis, and alpha power). Intermittent theta burst stimulation (iTBS) of the primary motor cortex (M1) is a non-invasive neuromodulation technique allowing controlled and focal enhancement of TMS cortical excitability and E/I of the stimulated hemisphere.
OBJECTIVE: Investigating to what extent E/I estimates scale with TMS excitability and how they relate to each other.
METHODS: M1 excitability (TMS) and several E/I estimates extracted from resting state EEG recordings were assessed before and after iTBS in a cohort of healthy subjects.
RESULTS: Enhancement of TMS M1 excitability, as measured through motor-evoked potentials (MEPs), and phase consistency of the cortex in high gamma band correlated with each other. Other measures of E/I showed some expected results, but no correlation with TMS excitability measures or strong consistency with each other.
CONCLUSIONS: EEG E/I estimates offer an intriguing opportunity to map cortical excitability non-invasively, with high spatio-temporal resolution and with a stimulus independent approach. While different EEG E/I estimates may reflect the activity of diverse excitatory-inhibitory circuits, spatial phase synchrony in the gamma band is the measure that best captures excitability changes in the primary motor cortex.