【摘要】 最大长序列(m序列)是在高刺激率条件下研究听觉诱发电位(AEP)线性/非线性成分的一种有效手段。但在实用中如何评估m序列的阶数选择对噪声抑制能力的影响是有待明确的问题。本研究主要采用两种类型实测数据评估m序列噪声抑制。根据m序列互相关法在去卷积计算过程中的两个计算步骤,即叠加平均和互相关,分别估算不同阶数(5~12阶)条件下自发脑电噪声抑制比,并选择7阶和9阶m序列进行非线性AEP实验。结果表明,m序列对自发脑电的噪声抑制比与随机噪声条件下的理论值完全符合,证实噪声抑制比主要取决于序列的总长度或总的记录时间。对于7阶和9阶m序列的线性/非线性成分进行相似性比较,提示AEP成分对阶数不敏感。本研究提供了一种选择m序列的更全面的解决方案,可更好地促进基于m序列的非线性AEP的应用。更多还原

【Abstract】 The maximum length sequence(m-sequence) has been successfully used to study the linear/nonlinear components of auditory evoked potential(AEP) with rapid stimulation. However, more study is needed to evaluate the effect of the m-sequence order in terms of the noise attenuation performance. This study aimed to address this issue using response-free electroencephalogram(EEG) and EEGs with nonlinear AEPs. We examined the noise attenuation ratios to evaluate the noise variation for the calculations of superimposed averaging and cross-correlation, respectively, which constitutes the main process in the deconvolution method using the dataset of spontaneous EEGs to simulate the cases of different orders(order 5 to 12) of m-sequences. And an experiment using m-sequences of order 7 and 9 was performed in true cases with substantial linear and nonlinear AEPs. The results demonstrate that the noise attenuation ratio is well agreed with the theoretical value derived from the properties of m-sequences on the random noise condition. The comparison of waveforms for AEP components from two m-sequences showed high similarity suggesting the insensitivity of AEP to the m-sequence order. This study provides a more comprehensive solution to the selection of m-sequences which will facilitate the feasible application on the nonlinear AEP with m-sequence method.更多还原