Ultrahigh-frequency EEG during fMRI: Pushing the limits of imaging-artifact correction
Ultrahigh-frequency EEG during fMRI: Pushing the limits of imaging-artifact correction
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DOI：
10.1016/j.neuroimage.2009.06.022
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发表时间：
2009-10-15
期刊：
影响因子：
5.7
通讯作者：
Ritter, Petra
中科院分区：
文献类型：
--
作者：
Freyer, Frank;Becker, Robert;Ritter, Petra
尽管同时进行EEG- fmri成像伪影校正的解决方案不断改进，但校正后的残余伪影对100 Hz以上超快频段的脑电信号谱仍有较大影响。然而，这个波段包含微妙但有价值的生理特征，如快速伽马振荡或与丘脑皮质和皮质神经元的尖峰相关的诱发高频（600赫兹）爆发。在这里，我们介绍了一种同时进行的EEG-fMRI方法，该方法集成了硬件和软件修改，以便在fMRI期间连续获取超快脑电图振荡。我们的方法基于并扩展了已有的平均伪影减法（AAS）方法。特别是对于超高频脑电图特征的恢复，原子吸收法需要恒定采样和恒定的成像伪影波形，以实现最佳的成像伪影校正。因此，我们调整了采集设置，使生理超高频脑电图和不变采样成像伪影都被捕获。此外，我们扩展了AAS算法来处理其他非采样相关的成像伪影变化源，如受试者运动。级联主成分分析最终去除剩余的成像伪影残差。我们提供了详细的评估平均超高频信号和非平均宽带脑电图频谱高达1khz。在被毫伏范围内的成像伪影影响的MR数据采集期间，成功地恢复了诱发纳伏特大小的高频爆发。与没有成像伪影的周期相比，它们表现出相同的平均振幅、延迟和波形，信噪比为72%。此外，我们还确定了一致的偶极子源。综上所述，使用该方法可以在fMRI期间连续监测超快脑电图振荡。(C) 2009爱思唯尔公司版权所有。
Although solutions for imaging-artifact correction in simultaneous EEG-fMRI are improving, residual artifacts after correction still considerably affect the EEG spectrum in the ultrafast frequency band above 100 Hz. Yet this band contains subtle but valuable physiological signatures such as fast gamma oscillations or evoked high-frequency (600 Hz) bursts related to spiking of thalamocortical and cortical neurons. Here we introduce a simultaneous EEG-fMRI approach that integrates hard and software modifications for continuous acquisition of ultrafast EEG oscillations during fMRI. Our approach is based upon and extends the established method of averaged artifact subtraction (AAS). Particularly for recovery of ultrahigh-frequency EEG signatures, AAS requires invariantly sampled and constant imaging-artifact waveforms to achieve optimal imaging-artifact correction. Consequently, we adjusted our acquisition setup such that both physiological ultrahigh-frequency EEG and invariantly sampled imaging artifacts were captured. In addition, we extended the AAS algorithm to cope with other, non-sampling related sources of imaging-artifact variations such as subject movements. A cascaded principal component analysis finally removed remaining imaging-artifact residuals. We provide a detailed evaluation of averaged ultrahigh-frequency signals and unaveraged broadband EEG spectra up to 1 kHz. Evoked nanovolt-sized high-frequency bursts were successfully recovered during periods of MR data acquisition afflicted by imaging artifacts in the millivolt range. Compared to periods without imaging artifacts they exhibited the same mean amplitudes, latencies and waveforms and a signal-to-noise ratio of 72%. Furthermore we identified consistent dipole sources. In conclusion, ultrafast EEG oscillations can be continuously monitored during fMRI using the proposed approach. (C) 2009 Elsevier Inc. All rights reserved.