Mu suppression - A good measure of the human mirror neuron system?
Mu suppression - A good measure of the human mirror neuron system?
复制标题
DOI：
10.1016/j.cortex.2016.03.019
复制
发表时间：
2016-09
期刊：
影响因子：
--
通讯作者：
Bishop DVM
中科院分区：
文献类型：
--
作者：
Hobson HM;Bishop DVM
Mu抑制被认为是人类镜像神经元系统（MNS）活动的标志。然而，mu频带（8-13 Hz）与对注意力波动敏感的alpha频带重叠，因此mu抑制可能会被注意力参与的变化所混淆。评估mu抑制的具体基线可能至关重要，但如何定义这一点几乎没有一致性。我们在61名典型成人中检查了mu抑制，这是迄今为止进行的最大的mu抑制研究。我们比较了不同的基线方法，并检查了中央和枕叶电极的活动，生物（手）和非生物（万花筒）移动刺激，以研究注意力和α活动在mu抑制中的参与。我们还研究了β功率的变化，这是MNS参与的另一个候选指标。当参与者进行手部运动时，我们观察到强烈的mu抑制仅限于中央电极，这表明mu确实对运动皮层的活动有反应。然而，当我们寻找与被动观察刺激相似的mu抑制特征时，基线方法被证明是至关重要的。只有当我们使用基于静态刺激的试验内基线时，才能在中央电极处看到生物刺激与非生物刺激的选择性抑制：与基于单独区块中的空白试验的基线相比，这种方法大大减少了抑制测量中的试验间差异。即使在这种最佳条件下，16-21%的参与者也没有表现出mu抑制。β功率的变化也与我们预测的MNS参与模式不匹配，似乎没有提供比mu更好的测量方法。我们的结论与最近的一项荟萃分析相反，该分析得出的结论是，μ抑制是检查镜像神经元活动的有效手段。我们认为，μ抑制可以用来索引人类MNS，但效果是弱的，不可靠的，容易混淆与α抑制。
Mu suppression has been proposed as a signature of the activity of the human mirror neuron system (MNS). However the mu frequency band (8–13 Hz) overlaps with the alpha frequency band, which is sensitive to attentional fluctuation, and thus mu suppression could potentially be confounded by changes in attentional engagement. The specific baseline against which mu suppression is assessed may be crucial, yet there is little consistency in how this is defined. We examined mu suppression in 61 typical adults, the largest mu suppression study so far conducted. We compared different methods of baselining, and examined activity at central and occipital electrodes, to both biological (hands) and non-biological (kaleidoscope) moving stimuli, to investigate the involvement of attention and alpha activity in mu suppression. We also examined changes in beta power, another candidate index of MNS engagement. We observed strong mu suppression restricted to central electrodes when participants performed hand movements, demonstrating that mu is indeed responsive to the activity of the motor cortex. However, when we looked for a similar signature of mu suppression to passively observed stimuli, the baselining method proved to be crucial. Selective suppression for biological versus non-biological stimuli was seen at central electrodes only when we used a within-trial baseline based on a static stimulus: this method greatly reduced trial-by-trial variation in the suppression measure compared with baselines based on blank trials presented in separate blocks. Even in this optimal condition, 16–21% of participants showed no mu suppression. Changes in beta power also did not match our predicted pattern for MNS engagement, and did not seem to offer a better measure than mu. Our conclusions are in contrast to those of a recent meta-analysis, which concluded that mu suppression is a valid means to examine mirror neuron activity. We argue that mu suppression can be used to index the human MNS, but the effect is weak and unreliable and easily confounded with alpha suppression.