Centre for Neuroscience, Indian Institute of Science, Bangalore 560012, India.
Centre for Neuroscience, Indian Institute of Science, Bangalore 560012, India
eNeuro. 2019 Aug 22;6(4). doi: 10.1523/ENEURO.0498-18.2019. Print 2019 Jul/Aug.
Alpha rhythm (8-13 Hz) is linked to relaxed mental state in humans. Earlier reports have shown that individuals can increase their alpha power if provided with a valid feedback, compared to controls who are provided invalid feedback. However, these results remain controversial, partly because controls may be in a different behavioral state, making it difficult to directly compare their alpha power with the valid group. We here address this issue by using an experimental paradigm in which an invalid feedback is given on a fraction of trials, such that both valid and invalid conditions can be obtained from the same participant. Using electroencephalography (EEG), we recorded alpha power from the occipital area from 24 humans (nine females) and played a feedback tone which could be valid (tone frequency proportional to alpha power), invalid (tone sequence from a previous valid trial; participants were unaware of this condition), or neutral (constant tone frequency). We found that during eyes closed-state, neurofeedback did not enhance alpha activity beyond pre-trained state within the experimental duration, probably because of saturation of alpha rhythmicity. However, for participants whose alpha power decreased over time within a trial, valid feedback helped them to sustain alpha more than invalid feedback. Further, alpha increase showed a weak negative correlation with their self-reported attentional load but was uncorrelated with relaxation levels. Our results reconcile many conflicting reports in the neurofeedback literature, and show that even under most stringent control, valid neurofeedback can help participants who are otherwise unable to sustain their alpha activity.
阿尔法节律（8-13Hz）与人的放松精神状态有关。早期的报告表明，与提供无效反馈的对照组相比，如果向个体提供有效反馈，他们的阿尔法功率可以增加。然而，这些结果仍存在争议，部分原因是对照组可能处于不同的行为状态，使得难以直接将其阿尔法功率与有效组进行比较。我们通过使用一种实验范式来解决这个问题，在该范式中，在一部分试验中提供无效反馈，从而可以从同一参与者中获得有效和无效两种条件。我们使用脑电图（EEG）记录了 24 名人类（9 名女性）枕叶区域的阿尔法功率，并播放了一个反馈音，该反馈音可以是有效的（音调频率与阿尔法功率成正比）、无效的（来自前一个有效试验的音调序列；参与者不知道这种情况）或中性的（恒定的音调频率）。我们发现，在闭眼状态下，神经反馈在实验持续时间内并没有在预先训练的状态之外增强阿尔法活动，这可能是由于阿尔法节律的饱和。然而，对于那些在试验过程中阿尔法功率随时间下降的参与者，有效反馈帮助他们比无效反馈更能维持阿尔法活动。此外，阿尔法的增加与他们自我报告的注意力负荷呈微弱的负相关，但与放松水平无关。我们的结果调和了神经反馈文献中的许多相互矛盾的报告，并表明，即使在最严格的控制下，有效的神经反馈也可以帮助那些否则无法维持其阿尔法活动的参与者。
