Dept ESAII, Centre for Biomedical Engineering Research, Universitat Politècnica de Catalunya, CIBER of Bioengineering, Biomaterials and Nanomedicine (CIBER-BBN), Barcelona, Spain.
Physiol Meas. 2011 Aug;32(8):1327-46. doi: 10.1088/0967-3334/32/8/021. Epub 2011 Jul 15.
Event-related brain potentials (ERPs) are the electrical response of the brain while performing a particular task. Methods traditionally used to study ERPs measure the amplitude and duration of the waveform in order to quantify the changes, being signal morphology dependent. However, the frequency characteristics of those events remain uncovered. The aim of this work was the study of new measures to characterize, by means of time-frequency representation (TFR) techniques, the ERPs recorded while subjects conducted a choice reaction time task (Ericksen flanker task) following the administration of different alprazolam doses. Several measures defined from energy, instantaneous frequency and group delay functions were obtained by means of TFR techniques applied to the Choi-Williams distribution (CWD) of EEG signals. These measures, which are signal morphology independent, were studied in four frequency bands, δ (0-4 Hz), θ (4-8 Hz), α (8-15 Hz), β (15-30 Hz), and for certain time periods. Based on these measures, differences between ERPs were analyzed by comparing the different response types (successes or successfully corrected failures) of the subject performing the task, and comparing the applied drug doses. For each subject, the CWD of EEG signals was applied in two different ways: (a) all ERPs were averaged per channel, and then the CWD was applied; (b) the CWD was applied to each one of the ERPs. When the CWD was applied to each ERP, the energy measures in the δ, θ and β bands, the instantaneous frequency measures in the α and β bands, and the group delay measures in the δ, θ and α bands showed a statistically significant level p < 0.0005 in the analysis of the response type. Also, the energy measures in the θ and β bands and the instantaneous frequency measures in the α band showed statistically significant differences (p < 0.0005) between placebo and low and high drug doses. In contrast, poor results were obtained when all epochs of each subject were averaged per channel. Finally, it was concluded that these results showed that the new proposed measures based on the energy offered a new and more robust way to characterize ERP signals.
事件相关脑电位（ERPs）是大脑在执行特定任务时的电反应。传统上用于研究 ERPs 的方法测量波形的幅度和持续时间，以量化变化，这取决于信号形态。然而，这些事件的频率特征仍然未知。这项工作的目的是研究新的措施，通过时频表示（TFR）技术，来描述在受试者进行选择反应时间任务（Ericksen 侧翼任务）时记录的 ERPs，同时给予不同剂量的阿普唑仑。通过 TFR 技术应用于 EEG 信号的 Choi-Williams 分布（CWD），获得了从能量、瞬时频率和群延迟函数定义的几种措施。这些与信号形态无关的措施，在四个频带（δ（0-4 Hz）、θ（4-8 Hz）、α（8-15 Hz）、β（15-30 Hz））和某些时间段内进行了研究。基于这些措施，通过比较受试者执行任务的不同反应类型（成功或成功纠正的失败）和比较应用的药物剂量，分析 ERPs 之间的差异。对于每个受试者，将 EEG 信号的 CWD 以两种不同的方式应用：（a）对每个通道的所有 ERPs 进行平均，然后应用 CWD；（b）对每个 ERP 应用 CWD。当 CWD 应用于每个 ERP 时，δ、θ 和 β 频带的能量测量值、α 和 β 频带的瞬时频率测量值以及 δ、θ 和 α 频带的群延迟测量值在反应类型的分析中显示出统计学上显著的水平 p < 0.0005。此外，θ 和 β 频带的能量测量值和 α 频带的瞬时频率测量值在安慰剂和低剂量和高剂量之间显示出统计学上的显著差异（p < 0.0005）。相比之下，当对每个受试者的所有时期进行平均时，得到的结果较差。最后得出结论，这些结果表明，基于能量的新提出的措施为 ERP 信号的特征描述提供了一种新的、更稳健的方法。
