Thakor N V, Kong X, Hanley D F
Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD 21205.
IEEE Trans Biomed Eng. 1995 Jan;42(1):42-51. doi: 10.1109/10.362920.
Injury-related changes in evoked potentials are studied with the aid of the coherence function, which effectively measures the degree of linear association between a pair of signals recorded during normal and abnormal states of the brain. The performance of an adaptive algorithm for estimating coherence function is studied, and the effects of additive noise on the estimated coherence function is discussed. Further, a linearity index is formulated and, through analysis and simulations, the index is shown to respond in a predictable manner to increasing nonlinearity while maintaining the robustness to the observation noise. Somatosensory evoked potentials are shown to be sensitive to injury resulting from acute cerebral hypoxia. We analyze the somatosensory evoked potentials recorded from anesthetized cats during inhalation of 8-9% oxygen gas mixtures and during recovery with 100% oxygen. Analyses of the experimental data show a very sharp drop in the magnitude coherence estimates during hypoxic injury and a corresponding rapid decline in the linearity index at the very early stages of the hypoxic injury. Thus, injury may lead to nonlinearities in the electrical response of the brain, and such measurements analyzed by the adaptive coherence estimation method may be used for diagnostic purposes.
借助相干函数研究诱发电位中与损伤相关的变化，该函数可有效测量大脑正常和异常状态下记录的一对信号之间的线性关联程度。研究了一种用于估计相干函数的自适应算法的性能，并讨论了加性噪声对估计相干函数的影响。此外，制定了一个线性指数，通过分析和模拟表明，该指数在保持对观测噪声鲁棒性的同时，对增加的非线性以可预测的方式做出响应。体感诱发电位显示对急性脑缺氧造成的损伤敏感。我们分析了在吸入8-9%氧气混合物期间以及用100%氧气恢复期间从麻醉猫记录的体感诱发电位。对实验数据的分析表明，在缺氧损伤期间，幅度相干估计值急剧下降，并且在缺氧损伤的非常早期阶段，线性指数相应迅速下降。因此，损伤可能导致大脑电反应的非线性，并且通过自适应相干估计方法分析的此类测量可用于诊断目的。
