Department of Psychology and Centre for Vision Research, York University, Toronto, ON, Canada.
Brain Behav. 2020 Dec;10(12):e01845. doi: 10.1002/brb3.1845. Epub 2020 Sep 23.
The application of repetitive transcranial magnetic stimulation (rTMS) for therapeutic use in visual-related disorders and its underlying mechanisms in the visual cortex is under-investigated. Additionally, there is little examination of rTMS adverse effects particularly with regards to visual and cognitive function. Neural plasticity is key in rehabilitation and recovery of function; thus, effective therapeutic strategies must be capable of modulating plasticity. Glutamate and γ-aminobutyric acid (GABA)-mediated changes in the balance between excitation and inhibition are prominent features in visual cortical plasticity.
We investigated the effects of low-frequency (1 Hz) rTMS to the visual cortex on levels of neurotransmitters GABA and glutamate to determine the therapeutic potential of 1 Hz rTMS for visual-related disorders. Two rTMS regimes commonly used in clinical applications were investigated: participants received rTMS to the visual cortex either in a single 20-min session or five accelerated 20-min sessions (not previously investigated at the visual cortex). Proton (1H) magnetic resonance spectroscopy for in vivo quantification of GABA (assessed via GABA+) and glutamate (assessed via Glx) concentrations was performed pre- and post-rTMS.
GABA+ and Glx concentrations were unaltered following a single session of rTMS to the visual cortex. One day of accelerated rTMS significantly reduced GABA+ concentration for up to 24 hr, with levels returning to baseline by 1-week post-rTMS. Basic visual and cognitive function remained largely unchanged.
Accelerated 1 Hz rTMS to the visual cortex has greater potential for approaches targeting plasticity or in cases with altered GABAergic responses in visual disorders. Notably, these results provide preliminary insight into a critical window of plasticity with accelerated rTMS (e.g., 24 hr) in which adjunct therapies may offer better functional outcome. We describe detailed procedures to enable further exploration of these protocols.
重复经颅磁刺激（rTMS）在视觉相关障碍的治疗应用及其在视觉皮层中的潜在机制尚未得到充分研究。此外，rTMS 的不良反应，特别是对视觉和认知功能的影响，也很少被检查。神经可塑性是康复和功能恢复的关键；因此，有效的治疗策略必须能够调节可塑性。谷氨酸和γ-氨基丁酸（GABA）介导的兴奋与抑制之间平衡的变化是视觉皮层可塑性的突出特征。
我们研究了低频（1 Hz）rTMS 对视觉皮层的影响，以确定 1 Hz rTMS 治疗视觉相关障碍的潜在疗效。研究了两种常用于临床应用的 rTMS 方案：参与者接受视觉皮层单次 20 分钟 rTMS 或五次加速 20 分钟 rTMS（以前在视觉皮层未进行过研究）。使用质子（1H）磁共振波谱法进行体内 GABA（通过 GABA+评估）和谷氨酸（通过 Glx 评估）浓度的定量。在 rTMS 前后进行了测量。
单次 rTMS 对视觉皮层后，GABA+和 Glx 浓度没有改变。一天的加速 rTMS 可显著降低 GABA+浓度长达 24 小时，rTMS 后 1 周内恢复到基线水平。基本视觉和认知功能基本保持不变。
加速的 1 Hz rTMS 对视觉皮层具有更大的潜力，可用于靶向可塑性的方法，或用于视觉障碍中 GABA 能反应改变的情况。值得注意的是，这些结果为加速 rTMS（例如 24 小时）的可塑性提供了初步的见解，在这段时间内，辅助治疗可能会提供更好的功能结果。我们描述了详细的程序，以进一步探索这些方案。
