Department of Neurosurgery, Osaka University Medical School, Suita City, Osaka, Japan.
Brain Stimul. 2011 Jan;4(1):28-37. doi: 10.1016/j.brs.2010.03.006. Epub 2010 Apr 18.
Though a cortical visual prosthesis is a promising method for treating severe visual disturbances, long-term blindness is known to depress visual cortex activity. We examined the use of repetitive transcranial magnetic stimulation (rTMS) with a navigation system as a direct functional assessment tool for the visual cortex.
We performed rTMS of the occipital cortex at three different stimulus frequencies (1 Hz, 5 Hz, and 20 Hz), on five stimulus targets around the calcarine fissure in 10 healthy subjects and 3 patients with visual impairment.
In the subjects with normal vision, phosphenes were mostly induced in the visual hemifield contralateral to the stimulation site, and stimulation on the targets inferior to the calcarine fissure predominantly induced phosphenes in the upper visual hemifield. High-frequency stimulation induced larger and complicated-shaped phosphenes at higher rates. The phosphenes induced rate and spatial distribution were altered in the blind patients.
The rTMS has the ability to directly assess the regional visual function of the occipital cortex both in normal-sighted subjects and blind patients. Precise targeting with a navigation system appropriately stimulated the lingual gyri, which contributed to consistently inducing the phosphenes in the upper visual fields. Atypical representation of the phosphenes in patients with visual impairment suggests the alteration of regional cortical excitations and spatial representation due to the cortical reorganization after the loss of visual inputs.
皮质视觉假体是治疗严重视觉障碍的一种有前途的方法，但众所周知，长期失明会抑制视觉皮层的活动。我们研究了使用导航系统的重复经颅磁刺激(rTMS)作为视觉皮层的直接功能评估工具。
我们在 10 名健康受试者和 3 名视力障碍患者的枕叶皮层上以三种不同的刺激频率(1 Hz、5 Hz 和 20 Hz)，在距枕沟三个不同的刺激靶点处进行 rTMS。
在视力正常的受试者中，闪光视觉大多出现在刺激部位对侧的视野中，而刺激在枕沟下方的目标处时，主要在视野的上半部分产生闪光视觉。高频刺激以更高的频率诱导更大和形状更复杂的闪光视觉。在盲患者中，闪光视觉的诱导率和空间分布发生了改变。
rTMS 具有直接评估正常视力受试者和盲患者枕叶皮层区域视觉功能的能力。导航系统的精确靶向适当地刺激了舌回，有助于在上半视野中持续产生闪光视觉。视力障碍患者闪光视觉的非典型表现提示由于视觉输入丧失后的皮质重组，导致区域皮质兴奋和空间代表发生改变。
