Spontaneous Neural Oscillations Bias Perception by Modulating Baseline Excitability
Spontaneous Neural Oscillations Bias Perception by Modulating Baseline Excitability
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DOI：
10.1523/jneurosci.1432-16.2016
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发表时间：
2017-01-25
影响因子：
5.3
通讯作者：
Busch, Niko A.
中科院分区：
文献类型：
--
作者：
Iemi, Luca;Chaumon, Maximilien;Busch, Niko A.
即使在没有任务或感觉输入的情况下，大脑也会表现出有组织的神经活动波动。这种自发活动的一个突出类型是阿尔法节律，它影响感知并与其他正在进行的神经活动相互作用。目前的假设是，前刺激α振荡减少的状态表明神经兴奋性增强，导致感知敏锐度提高。然而，在知觉任务中，兴奋性的变化如何表现在行为水平上仍然存在争议。我们通过比较两种描述自发α功率对信号检测影响的替代模型来解决这个问题。第一个模型假设降低的α功率增加基线兴奋性，放大对信号和噪声的响应，预测自由检测标准对灵敏度没有影响。第二个模型预测，降低阿尔法功率增加了感官反应的逐个试验精度，从而提高了灵敏度。我们在人类的两个EEG实验中测试了这些模型，在那里我们使用信号检测框架分析了刺激前α功率对视觉检测和辨别的影响。这两个实验都提供了强有力的证据，表明α功率降低反映了更自由的检测标准，而不是与基线模型一致的灵敏度提高。换句话说，当任务需要检测刺激存在与不存在时，减少的α振荡使观察者更有可能报告刺激，而不管实际刺激存在与否。与以前的解释相反，这些结果表明，减少α振荡的状态增加了感觉系统的整体基线兴奋性，而不影响感知敏锐度。
The brain exhibits organized fluctuations of neural activity, even in the absence of tasks or sensory input. A prominent type of such spontaneous activity is the alpha rhythm, which influences perception and interacts with other ongoing neural activity. It is currently hypothesized that states of decreased prestimulus alpha oscillations indicate enhanced neural excitability, resulting in improved perceptual acuity. Nevertheless, it remains debated how changes in excitability manifest at the behavioral level in perceptual tasks. We addressed this issue by comparing two alternative models describing the effect of spontaneous alpha power on signal detection. The first model assumes that decreased alpha power increases baseline excitability, amplifying the response to both signal and noise, predicting a liberal detection criterion with no effect on sensitivity. The second model predicts that decreased alpha power increases the trial-by-trial precision of the sensory response, resulting in improved sensitivity. We tested these models in two EEG experiments in humans where we analyzed the effects of prestimulus alpha power on visual detection and discrimination using a signal detection framework. Both experiments provide strong evidence that decreased alpha power reflects a more liberal detection criterion, rather than improved sensitivity, consistent with the baseline model. In other words, when the task requires detecting stimulus presence versus absence, reduced alpha oscillations make observers more likely to report the stimulus regardless of actual stimulus presence. Contrary to previous interpretations, these results suggest that states of decreased alpha oscillations increase the global baseline excitability of sensory systems without affecting perceptual acuity.