The phenomenon of mental fatigue has recently been investigated extensively by means of the EEG. Studies deploying spectral analysis consistently reported an increase of spectral power in the lower frequencies with increasing time-on-task, whereas event-related studies observed decreases in various measures related to task engagement and attentional resources. The results from these two lines of research cannot be aligned easily. (Frontal) theta power has been linked to cognitive control and was found to increase with time-on-task. In contrast, theoretical frameworks on mental fatigue suggest a decline in task-engagement as causal for the performance decline observed in mental fatigue. The goal of the present study was to investigate mental fatigue in time–frequency space using linear regression on single-trial data in order to obtain a better understanding about how time-on-task affects theta oscillatory activity. A data-driven analysis approach indicated an increase of alpha and theta power during the intertrial interval. In contrast, task-related theta activity declined. This reduction of stimulus-locked theta power may be interpreted as a reduction of task engagement with increasing mental fatigue. The increase of theta spectral power in the intertrial interval, moreover, could possibly be explained by an increased idling of cognitive control networks. Alternatively, it might be the case that the increase of theta power with time-on-task is a by-product an alpha power increase. As alpha peak frequency systematically decreases with time-on-task, the theta band might be affected as well.

中文翻译：

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任务相关和与任务无关的 theta 活动中的任务时间的反向影响

最近通过脑电图对精神疲劳现象进行了广泛的研究。部署频谱分析的研究一致报告说，随着任务时间的增加，较低频率的频谱功率增加，而与事件相关的研究观察到与任务参与和注意力资源相关的各种措施的减少。这两个研究方向的结果不容易对齐。（正面）theta 功率与认知控制有关，并且发现随着任务时间的增加而增加。相比之下，关于精神疲劳的理论框架表明，任务参与度下降是精神疲劳中观察到的绩效下降的原因。本研究的目的是使用对单次试验数据的线性回归来研究时频空间中的精神疲劳，以便更好地了解任务时间如何影响 theta 振荡活动。数据驱动的分析方法表明，在试验间隔期间 alpha 和 theta 功率增加。相比之下，与任务相关的 theta 活动下降。这种刺激锁定θ功率的降低可以解释为随着精神疲劳的增加而减少任务参与。此外，试验间期θ谱功率的增加可能是由于认知控制网络的空闲增加所致。或者，θ 功率随任务时间的增加可能是阿尔法功率增加的副产品。