Abuleil Dania, Gorbet Diana, McCulloch Daphne L, Cohan Remy, Steeves Jennifer Evelyn Kate, Bang Ji Won, Chan Kevin C, Thompson Benjamin
School of Optometry and Vision Science, University of Waterloo, Waterloo, ON, Canada.
Centre for Vision Research, York University, Toronto, ON, Canada.
Front Neurosci. 2025 Oct 15;19:1639838. doi: 10.3389/fnins.2025.1639838. eCollection 2025.
Anodal direct current stimulation (a-tDCS) of the visual cortex is a potential rehabilitation tool for vision disorders such as amblyopia and macular degeneration. However, the underlying neural mechanisms are currently unknown. When applied to the human motor cortex, a-tDCS reduces the concentration of gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter that modulates neuroplasticity. Our primary aim was to assess whether the same a-tDCS paradigm alters local GABA concentration when applied to the healthy primary visual cortex. We also measured the effect of a-tDCS on visual cortex resting-state connectivity and sought to replicate reported observations of an association between visual cortex GABA concentration and the dynamics of binocular rivalry.
Fourteen participants with normal vision completed two brain imaging sessions at least 48 hours apart. In each session, binocular rivalry dynamics, primary visual cortex GABA and glutamate-glutamine (Glx) concentrations (via magnetic resonance spectroscopy (MRS)) and resting-state functional connectivity (via task-free fMRI) were measured at baseline. Real or sham a-tDCS (20 min, 2mA) was then applied to the visual cortex in a randomized sequence followed by a second set of MRS and fMRI measurements.
No between-session effects of a-tDCS on GABA or Glx concentration or resting-state functional connectivity were observed. A pre-planned within-session analysis revealed a significant increase in Glx following a-tDCS that did not withstand multiple comparisons correction. No consistent relationships between binocular rivalry dynamics and GABA concentration were apparent.
Together, our results suggest that a-tDCS effects on the visual cortex may differ from the GABA-associated mechanism in motor cortex.
对视觉皮层进行阳极直流电刺激（a-tDCS）是一种针对弱视和黄斑变性等视力障碍的潜在康复工具。然而，其潜在的神经机制目前尚不清楚。当应用于人类运动皮层时，a-tDCS会降低γ-氨基丁酸（GABA）的浓度，GABA是一种调节神经可塑性的抑制性神经递质。我们的主要目的是评估相同的a-tDCS模式应用于健康的初级视觉皮层时是否会改变局部GABA浓度。我们还测量了a-tDCS对视觉皮层静息态连接性的影响，并试图重复已报道的视觉皮层GABA浓度与双眼竞争动态之间关联的观察结果。
14名视力正常的参与者至少间隔48小时完成两次脑成像检查。在每次检查中，在基线时测量双眼竞争动态、初级视觉皮层GABA和谷氨酸-谷氨酰胺（Glx）浓度（通过磁共振波谱（MRS））以及静息态功能连接性（通过无任务功能磁共振成像（fMRI））。然后以随机顺序对视觉皮层施加真实或假的a-tDCS（20分钟，2毫安），随后进行第二轮MRS和fMRI测量。
未观察到a-tDCS对GABA或Glx浓度或静息态功能连接性的检查间效应。预先计划的检查内分析显示，a-tDCS后Glx显著增加，但未通过多重比较校正。双眼竞争动态与GABA浓度之间没有明显的一致关系。
总体而言，我们的结果表明，a-tDCS对视觉皮层的影响可能与运动皮层中与GABA相关的机制不同。
