网络介导的对重复刺激的反应的时间特性取决于视网膜神经节细胞的类型。
Temporal properties of network-mediated responses to repetitive stimuli are dependent upon retinal ganglion cell type.
作者信息
Im Maesoon, Fried Shelley I
机构信息
VA Boston Healthcare System, 150 South Huntington Avenue, Boston, MA 02130, USA. Department of Neurosurgery, Massachusetts General Hospital and Harvard Medical School, 50 Blossom Street, Boston, MA 02114, USA. Present address: Department of Ophthalmology, Henry Ford Hospital, 1 Ford Place, Detroit, MI 48202, USA.
出版信息
J Neural Eng. 2016 Apr;13(2):025002. doi: 10.1088/1741-2560/13/2/025002. Epub 2016 Feb 23.
OBJECTIVE
To provide artificially-elicited vision that is temporally dynamic, retinal prosthetic devices will need to repeatedly stimulate retinal neurons. However, given the diversity of physiological types of retinal ganglion cells (RGCs) as well as the heterogeneity of their responses to electric stimulation, temporal properties of RGC responses have not been adequately investigated. Here, we explored the cell type dependence of network-mediated RGC responses to repetitive electric stimulation at various stimulation rates.
APPROACH
We examined responses of ON and OFF types of RGCs in the rabbit retinal explant to five consecutive stimuli with varying inter-stimulus intervals (10-1000 ms). Each stimulus was a 4 ms long monophasic sinusoidal cathodal current, which was applied epiretinally via a conical electrode. Spiking activity of targeted RGCs was recorded using a cell-attached patch electrode.
MAIN RESULTS
ON and OFF cells had distinct responses to repetitive stimuli. Consistent with earlier studies, OFF cells always generated reduced responses to subsequent stimuli compared to responses to the first stimulus. In contrast, a new stimulus to ON cells suppressed all pending/ongoing responses from previous stimuli and initiated its own response that was remarkably similar to the response from a single stimulus in isolation. This previously unreported 'reset' behavior was observed exclusively and consistently in ON cells. These contrasts between ON and OFF cells created a range of stimulation rates (4-7 Hz) that maximized the ratio of the responses arising in ON versus OFF cells.
SIGNIFICANCE
Previous clinical testing reported that subjects perceive bright phosphenes (ON responses) and also prefer stimulation rates of 5-7 Hz. Our results suggest that responses of ON cells are weak at high rates of stimulation (> ∼7 Hz) due to the reset while responses of OFF cells are strong at low rates (< ∼4 Hz) due to reduced desensitization, both reducing the ratio of ON to OFF responses. In combination with previous results indicating that responses in ON cells more closely match physiological patterns (Im and Fried 2015 J. Physiol. 593 3577-96), our results offer a potential reason for the user preference of intermediate rates (5-7 Hz).
目的
为了提供具有时间动态性的人工诱发视觉，视网膜假体装置将需要反复刺激视网膜神经元。然而，鉴于视网膜神经节细胞（RGCs）生理类型的多样性以及它们对电刺激反应的异质性，RGC反应的时间特性尚未得到充分研究。在此，我们探讨了在不同刺激速率下，网络介导的RGC对重复电刺激反应的细胞类型依赖性。
方法
我们检测了兔视网膜外植体中ON型和OFF型RGC对五个连续刺激的反应，刺激间隔时间不同（10 - 1000毫秒）。每个刺激是一个持续4毫秒的单相正弦阴极电流，通过锥形电极经视网膜表面施加。使用细胞贴附式膜片电极记录目标RGC的放电活动。
主要结果
ON型和OFF型细胞对重复刺激有不同反应。与早期研究一致，OFF型细胞对后续刺激的反应总是比对第一个刺激的反应减弱。相比之下，对ON型细胞的新刺激会抑制来自先前刺激的所有未完成/正在进行的反应，并引发其自身的反应，该反应与单独一个刺激引发的反应非常相似。这种先前未报道的“重置”行为仅在ON型细胞中一致地观察到。ON型和OFF型细胞之间的这些差异产生了一系列刺激速率（4 - 7赫兹），使ON型细胞与OFF型细胞产生的反应比率最大化。
意义
先前的临床试验报告称，受试者能感知明亮的光幻视（ON反应），并且也更喜欢5 - 7赫兹的刺激速率。我们的结果表明，由于重置，ON型细胞在高刺激速率（> ∼7赫兹）下反应较弱，而OFF型细胞在低刺激速率（< ∼4赫兹）下由于脱敏减少反应较强，这两者都降低了ON与OFF反应的比率。结合先前的结果表明ON型细胞中的反应更紧密地匹配生理模式（Im和Fried，2015年，《生理学杂志》593卷，3577 - 3596页），我们的结果为用户偏好中等速率（5 - 7赫兹）提供了一个潜在原因。
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