Heinrich-Heine-University Düsseldorf, Medical Faculty, Institute of Clinical Neuroscience and Medical Psychology, Universitätsstrasse 1, D-40225 Düsseldorf, Germany.
Neuroimage. 2012 Sep;62(3):1965-74. doi: 10.1016/j.neuroimage.2012.05.071. Epub 2012 Jun 1.
Extensive work using magneto- and electroencephalography (M/EEG) suggests that cortical alpha activity represents a top-down controlled gating mechanism employed by processes like attention across different modalities. However, it is not yet clear to what extent this presumed gating function of alpha activity also applies to the processing of pain. In the current study, a spatial attention paradigm was employed requiring subjects to attend to painful laser stimuli on one hand while ignoring stimuli on the other hand. Simultaneously, brain activity was recorded with MEG. In order to disentangle pre- and post-stimulus effects of attention, alpha activity was analyzed during time windows in anticipation of and in response to painful laser stimulation. Painful laser stimuli led to a suppression of alpha activity over both ipsi- and contralateral primary somatosensory areas irrespective if they were attended or ignored. Spatial attention was associated with a lateralization of anticipatory pre-stimulus alpha activity. Alpha activity was lower over primary somatosensory areas when the contralateral hand was attended compared to when the ipsilateral hand was attended, in line with the notion that oscillatory alpha activity regulates the flow of incoming information by engaging and/or disengaging early sensory areas. On the contrary, post-stimulus alpha activity, for stimuli on either hand, was consistently decreased with attention over contralateral areas. Most likely, this finding reflects an increased cortical activation and enhanced alerting if a painful stimulus is attended. The present results show that spatial attention results in a modulation of both pre- and post-stimulus alpha activity associated with pain. This flexible regulation of alpha activity matches findings from other modalities. We conclude that the assumed functional role of alpha activity as a top-down controlled gating mechanism includes pain processing and most likely represents a unified mechanism used throughout the brain.
使用磁共振和脑电图（M/EEG）的广泛研究表明，皮质α活动代表了一种自上而下的控制门控机制，用于注意力等过程在不同模式下的作用。然而，目前尚不清楚这种假定的α活动的门控功能在多大程度上也适用于疼痛的处理。在当前的研究中，采用了空间注意范式，要求受试者一方面注意疼痛的激光刺激，另一方面忽略其他刺激。同时，用 MEG 记录大脑活动。为了区分注意力的刺激前和刺激后效应，在对疼痛激光刺激的预期和响应期间分析α活动。无论是否受到关注，疼痛的激光刺激都会导致对侧和同侧初级体感区域的α活动抑制。空间注意力与预期前刺激α活动的侧化有关。与同侧手相比，当对侧手受到关注时，初级体感区域的α活动降低，这与振荡α活动通过参与和/或脱离早期感觉区域来调节传入信息的流动的观点一致。相反，对于任一手的刺激，注意力会导致刺激后α活动一致减少。最有可能的是，如果关注疼痛刺激，这一发现反映了皮质激活的增加和警觉性的提高。本研究结果表明，空间注意力会导致与疼痛相关的刺激前和刺激后α活动的调节。这种灵活的α活动调节与其他模式的发现相匹配。我们得出结论，假定的α活动作为自上而下的控制门控机制的功能作用包括疼痛处理，并且很可能代表了整个大脑中使用的统一机制。
