Bland Nicholas S, Mattingley Jason B, Sale Martin V
Queensland Brain Institute, University of Queensland, St Lucia, QLD, Australia.
School of Psychology, University of Queensland, St Lucia, QLD, Australia.
Front Psychol. 2018 Mar 9;9:304. doi: 10.3389/fpsyg.2018.00304. eCollection 2018.
Phase synchronization drives connectivity between neural oscillators, providing a flexible mechanism through which information can be effectively and selectively routed between task-relevant cortical areas. The ability to keep track of objects moving between the left and right visual hemifields, for example, requires the integration of information between the two cerebral hemispheres. Both animal and human studies have suggested that coherent (or phase-locked) gamma oscillations (30-80 Hz) might underlie this ability. While most human evidence has been strictly correlational, high-density transcranial alternating current stimulation (HD-tACS) has been used to manipulate ongoing interhemispheric gamma phase relationships. Previous research showed that 40 Hz tACS delivered bilaterally over human motion complex could bias the perception of a bistable ambiguous motion stimulus (Helfrich et al., 2014). Specifically, this work showed that in-phase (0° offset) stimulation boosted endogenous interhemispheric gamma coherence and biased perception toward the horizontal (whereby visual tokens moved visual hemifields-requiring interhemispheric integration). By contrast, anti-phase (180° offset) stimulation decreased interhemispheric gamma coherence and biased perception toward the vertical (whereby tokens moved separate visual hemifields). Here we devised a multiple object tracking arena comprised of four quadrants whereby discrete objects moved either entirely within the left and right visual hemifields, or could cross freely between visual hemifields, thus requiring interhemispheric integration. Using the same HD-tACS montages as Helfrich et al. (2014), we found no phase-specific effect of 40 Hz stimulation on overall tracking performance. While tracking performance was generally lower during -hemifield trials (presumably reflecting a cost of integration), this difference was unchanged by in- vs. anti-phase stimulation. Our null results could be due to a failure to reliably modulate coherence in our study, or that our task does not rely as heavily on this network of coherent gamma oscillations as other visual integration paradigms.
相位同步驱动神经振荡器之间的连通性，提供了一种灵活的机制，通过该机制信息可以在与任务相关的皮质区域之间有效且有选择地进行路由。例如，追踪在左右视觉半视野之间移动的物体的能力需要两个大脑半球之间的信息整合。动物和人类研究均表明，相干（或锁相）伽马振荡（30 - 80赫兹）可能是这种能力的基础。虽然大多数人类证据只是严格的相关性证据，但高密度经颅交流电刺激（HD - tACS）已被用于操纵正在进行的半球间伽马相位关系。先前的研究表明，在人类运动复合体上双侧施加40赫兹的tACS可以使对双稳态模糊运动刺激的感知产生偏差（赫尔弗里希等人，2014年）。具体而言，这项研究表明，同相（0°偏移）刺激增强了内源性半球间伽马相干性，并使感知偏向水平方向（即视觉标记在需要半球间整合的视觉半视野之间移动）。相比之下，反相（180°偏移）刺激降低了半球间伽马相干性，并使感知偏向垂直方向（即标记在不同的视觉半视野之间移动）。在这里，我们设计了一个由四个象限组成的多物体跟踪区域，离散物体要么完全在左右视觉半视野内移动，要么可以在视觉半视野之间自由交叉，因此需要半球间整合。使用与赫尔弗里希等人（2014年）相同的HD - tACS电极片组合，我们发现40赫兹刺激对整体跟踪性能没有相位特异性影响。虽然在半视野试验期间跟踪性能通常较低（可能反映了整合成本），但同相刺激与反相刺激并没有改变这种差异。我们的零结果可能是由于在我们的研究中未能可靠地调节相干性，或者是因为我们的任务不像其他视觉整合范式那样严重依赖于这个相干伽马振荡网络。
