Fluctuations in oscillatory brain activity have been shown to co-occur with variations in task performance. More recently, part of these fluctuations has been attributed to long-term (>1hr) monotonous trends in the power and frequency of alpha oscillations (8-13 Hz). Here we tested whether these time-on-task changes in EEG activity are limited to activity in the alpha band and whether they are linked to task performance. Thirty-six participants performed 900 trials of a two-alternative forced choice visual discrimination task with confidence ratings. Pre- and post-stimulus spectral power (1-40Hz) and aperiodic (i.e., non-oscillatory) components were compared across blocks of the experimental session and tested for relationships with behavioural performance. We found that time-on-task effects on oscillatory EEG activity were primarily localised within the alpha band, with alpha power increasing and peak alpha frequency decreasing over time, even when controlling for aperiodic contributions. Aperiodic, broadband activity on the other hand did not show time-on-task effects in our data set. Importantly, time-on-task effects in alpha frequency and power explained variability in single-trial reaction times. Moreover, controlling for time-on-task effectively removed the relationships between alpha activity and reaction times. However, time-on-task effects did not affect other EEG signatures of behavioural performance, including post-stimulus predictors of single-trial decision confidence. Therefore, our results dissociate alpha-band brain-behaviour relationships that can be explained away by time-on-task from those that remain after accounting for it - thereby further specifying the potential functional roles of alpha in human visual perception.

中文翻译：

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表征振荡和非周期性脑电图成分的任务时间效应及其与视觉任务表现的共同变化。

大脑振荡活动的波动已被证明与任务表现的变化同时发生。最近，这些波动的一部分归因于 α 振荡（8-13 Hz）的功率和频率的长期（>1 小时）单调趋势。在这里，我们测试了脑电图活动的这些任务时间变化是否仅限于阿尔法带的活动以及它们是否与任务表现相关。 36 名参与者进行了 900 次两项强制选择视觉辨别任务的试验，并进行了置信度评级。在实验过程中比较刺激前和刺激后的频谱功率（1-40Hz）和非周期性（即非振荡）分量，并测试其与行为表现的关系。我们发现，任务时间对振荡脑电图活动的影响主要集中在 α 波段内，随着时间的推移，α 功率增加，峰值 α 频率降低，即使在控制非周期性贡献时也是如此。另一方面，非周期性宽带活动在我们的数据集中没有显示出任务时间效应。重要的是，α频率和功率的任务时间效应解释了单次试验反应时间的变异性。此外，控制任务时间有效地消除了阿尔法活动和反应时间之间的关系。然而，任务时间效应并不影响行为表现的其他脑电图特征，包括单次试验决策信心的刺激后预测因子。因此，我们的结果将可以通过任务时间来解释的α波段大脑行为关系与在考虑任务时间后仍然存在的关系区分开来，从而进一步明确了α在人类视觉感知中的潜在功能作用。