Long-term correlation of the electrocorticogram as a bioindicator of brain exposure to ionizing radiation

Understanding the effects of radiation and its possible influence on the nervous system are of great clinical interest. However, there have been few electrophysiological studies on brain activity after exposure to ionizing radiation (IR). A new methodological approach regarding the assessment of the possible effects of IR on brain activity is the use of linear and nonlinear mathematical methods in the analysis of complex time series, such as brain oscillations measured using the electrocorticogram (ECoG). The objective of this study was to use linear and nonlinear mathematical methods as biomarkers of gamma radiation regarding cortical electrical activity. Adult Wistar rats were divided into 3 groups: 1 control and 2 irradiated groups, evaluated at 24 h (IR24) and 90 days (IR90) after exposure to 18 Gy of gamma radiation from a cobalt-60 radiotherapy source. The ECoG was analyzed using power spectrum methods for the calculation of the power of delta, theta, alpha and beta rhythms and by means of the α-exponent of the detrended fluctuation analysis (DFA). Using both mathematical methods it was possible to identify changes in the ECoG, and to identify significant changes in the pattern of the recording at 24 h after irradiation. Some of these changes were persistent at 90 days after exposure to IR. In particular, the theta wave using the two methods showed higher sensitivity than other waves, suggesting that it is a possible biomarker of exposure to IR.

探究辐射的生物学效应及其对神经系统的潜在影响，具有重要的临床研究价值。然而，目前针对电离辐射（ionizing radiation, IR）暴露后脑活动的电生理学研究仍较为匮乏。针对IR对脑活动潜在影响的评估，一种新兴的方法论途径是采用线性与非线性数学方法分析复杂时序信号——例如通过脑皮层电图（electrocorticogram, ECoG）记录的脑振荡信号。本研究旨在借助线性与非线性数学方法，将其作为伽马辐射暴露后皮层电活动的生物标志物。将成年Wistar大鼠分为3组：1组为对照组，2组为辐照组，分别在接受18戈瑞（Gray, Gy）钴-60放射源伽马辐射后的24小时（记为IR24组）与90天（记为IR90组）进行评估。本研究采用功率谱分析法计算德尔塔（delta）、西塔（theta）、阿尔法（alpha）与贝塔（beta）节律的功率，并通过去趋势波动分析（detrended fluctuation analysis, DFA）的α指数对ECoG信号进行分析。通过这两种数学分析方法，均可识别出ECoG信号的变化，并可检测到辐照后24小时脑电记录模式的显著改变。其中部分变化在IR暴露后90天时仍持续存在。尤为关键的是，通过两种分析方法均显示西塔波相较于其他脑电波具有更高的敏感性，提示其可作为IR暴露的潜在生物标志物。