INSERM Unité 992 Cognitive Neuroimaging, and Commissariat à l'Energie Atomique, Direction des Sciences du Vivant, Institut d'Imagerie Biomédicale, NeuroSpin, F-91191 Gif-sur-Yvette, France.
J Neurosci. 2011 Mar 9;31(10):3813-20. doi: 10.1523/JNEUROSCI.4697-10.2011.
Using simultaneous electroencephalography as a measure of ongoing activity and functional magnetic resonance imaging (fMRI) as a measure of the stimulus-driven neural response, we examined whether the amplitude and phase of occipital alpha oscillations at the onset of a brief visual stimulus affects the amplitude of the visually evoked fMRI response. When accounting for intrinsic coupling of alpha amplitude and occipital fMRI signal by modeling and subtracting pseudo-trials, no significant effect of prestimulus alpha amplitude on the evoked fMRI response could be demonstrated. Regarding the effect of alpha phase, we found that stimuli arriving at the peak of the alpha cycle yielded a lower blood oxygenation level-dependent (BOLD) fMRI response in early visual cortex (V1/V2) than stimuli presented at the trough of the cycle. Our results therefore show that phase of occipital alpha oscillations impacts the overall strength of a visually evoked response, as indexed by the BOLD signal. This observation complements existing evidence that alpha oscillations reflect periodic variations in cortical excitability and suggests that the phase of oscillations in postsynaptic potentials can serve as a mechanism of gain control for incoming neural activity. Finally, our findings provide a putative neural basis for observations of alpha phase dependence of visual perceptual performance.
我们使用同时进行的脑电图来测量持续活动，使用功能磁共振成像（fMRI）来测量刺激驱动的神经反应，研究在短暂视觉刺激开始时，枕部α 节律的幅度和相位是否会影响视觉诱发 fMRI 反应的幅度。通过建模和减去伪试验来解释和扣除α 幅度与枕部 fMRI 信号的内在耦合，我们发现，在视觉皮层（V1/V2）中，与在周期低谷时呈现的刺激相比，在α 周期峰值时到达的刺激产生的血氧水平依赖（BOLD）fMRI 反应较低。因此，我们的结果表明，枕部α 节律的相位会影响视觉诱发反应的整体强度，其指标为 BOLD 信号。这一观察结果补充了现有的证据，即α 节律反映了皮质兴奋性的周期性变化，并表明突触后电位的振荡相位可以作为传入神经活动的增益控制机制。最后，我们的发现为观察视觉感知性能的α 相位依赖性提供了一个潜在的神经基础。
