Craddock Matt, Poliakoff Ellen, El-Deredy Wael, Klepousniotou Ekaterini, Lloyd Donna M
University of Leeds, Leeds, UK.
University of Manchester, Manchester, UK.
Neuropsychologia. 2017 Feb;96:9-18. doi: 10.1016/j.neuropsychologia.2016.12.030. Epub 2016 Dec 29.
Fluctuations of pre-stimulus oscillatory activity in the somatosensory alpha band (8-14Hz) observed using human EEG and MEG have been shown to influence the detection of supra- and peri-threshold somatosensory stimuli. However, some reports of touch occur even without a stimulus. We investigated the possibility that pre-stimulus alpha oscillations might also influence these false reports of touch - known as tactile misperceptions. We recorded EEG while participants performed the Somatic Signal Detection Task (SSDT), in which participants must detect brief, peri-threshold somatosensory targets. We found that pre-stimulus oscillatory power in the somatosensory alpha range exhibited a negative linear relationship with reporting of touch at electrode clusters over both contralateral and ipsilateral somatosensory regions. As pre-stimulus alpha power increased, the probability of reporting a touch declined; as it decreased, the probability of reporting a touch increased. This relationship was stronger on trials without a somatosensory stimulus than on trials with a somatosensory stimulus, although was present for both trial types. Spatio-temporal cluster-based permutation analysis also found that pre-stimulus alpha was lower on trials when touch was reported - irrespective of whether it was present - over contralateral and ipsilateral somatosensory cortices, as well as left frontocentral areas. We argue that alpha power may reflect changes in response criterion rather than sensitivity alone. Low alpha power relates to a low barrier to reporting a touch even when one is not present, while high alpha power is linked to less frequent reporting of touch overall.
利用人类脑电图（EEG）和脑磁图（MEG）观察到，体感α波段（8 - 14Hz）中刺激前振荡活动的波动已被证明会影响超阈值和阈上体感刺激的检测。然而，一些关于触觉的报告显示，即使没有刺激也会出现。我们研究了刺激前α振荡可能也会影响这些被称为触觉错觉的触觉错误报告的可能性。我们在参与者执行躯体信号检测任务（SSDT）时记录脑电图，在该任务中，参与者必须检测短暂的、阈上体感目标。我们发现，在对侧和同侧体感区域的电极簇上，体感α范围内的刺激前振荡功率与触觉报告呈负线性关系。随着刺激前α功率增加，报告触觉的概率下降；随着其降低，报告触觉的概率增加。这种关系在没有体感刺激的试验中比在有体感刺激的试验中更强，尽管两种试验类型中都存在。基于时空簇的置换分析还发现，无论是否存在触觉，在对侧和同侧体感皮层以及左额中央区域，当报告触觉时，刺激前α在试验中较低。我们认为，α功率可能反映的是反应标准的变化，而不仅仅是敏感性。低α功率与即使不存在触觉也报告触觉的低阈值相关，而高α功率与总体上较少报告触觉相关。
