Sahib Ashish Kaul, Mathiak Klaus, Erb Michael, Elshahabi Adham, Klamer Silke, Scheffler Klaus, Focke Niels K, Ethofer Thomas
Werner Reichardt Centre for Integrative Neuroscience, Tübingen, Germany.
Department of Biomedical Magnetic Resonance, University Hospital Tübingen, Tübingen, Germany.
Magn Reson Med. 2016 Dec;76(6):1805-1813. doi: 10.1002/mrm.26073. Epub 2016 Jan 9.
To assess the impact of colored noise on statistics in event-related functional MRI (fMRI) (visual stimulation using checkerboards) acquired by simultaneous multislice imaging enabling repetition times (TRs) between 2.64 to 0.26 s.
T-values within the visual cortex obtained with analysis tools that assume a first-order autoregressive plus white noise process (AR(1)+w) with a fixed AR coefficient versus higher-order AR models with spatially varying AR coefficients were compared. In addition, dependency of T-values on correction of physiological noise (respiration, heart rate) was evaluated.
Optimal statistical power was obtained for a TR of 0.33 s, but T-values as obtained by AR(1)+w models were strongly dependent on the predefined AR coefficients in fMRI with short TRs which required higher-order AR models to achieve stable statistics. Direct estimation of AR coefficients revealed the highest values within the default mode network while physiological noise had little influence on statistics in cortical structures.
Colored noise in event-related fMRI obtained at short TRs originates mainly from neural sources and calls for more sophisticated correction of serial autocorrelations which cannot be achieved with standard methods relying on AR(1)+w models with globally fixed AR coefficients. Magn Reson Med 76:1805-1813, 2016. © 2016 International Society for Magnetic Resonance in Medicine.
评估在使用同时多层成像技术获取的事件相关功能磁共振成像（fMRI）（使用棋盘格进行视觉刺激）中，有色噪声对统计结果的影响，该成像技术可实现2.64至0.26秒之间的重复时间（TR）。
比较使用假设一阶自回归加白噪声过程（AR(1)+w）且具有固定AR系数的分析工具与具有空间变化AR系数的高阶AR模型在视觉皮层内获得的T值。此外，评估T值对生理噪声（呼吸、心率）校正的依赖性。
在TR为0.33秒时获得了最佳统计功效，但AR(1)+w模型获得的T值在短TR的fMRI中强烈依赖于预定义的AR系数，这需要高阶AR模型来实现稳定的统计。AR系数的直接估计显示默认模式网络内的值最高，而生理噪声对皮质结构的统计影响很小。
在短TR下获得的事件相关fMRI中的有色噪声主要源于神经源，需要对序列自相关进行更复杂的校正，这是依赖具有全局固定AR系数的AR(1)+w模型的标准方法无法实现的。《磁共振医学》76:1805 - 1813, 2016。© 2016国际磁共振医学学会。
