猫视网膜神经节细胞显示对长时间光栅刺激的弱图形适应和明显的图形易化作用(英文)

The cat's retinal ganglion cells show weak pattern adaptation but significant pattern facilitation to prolonged grating stimuli

图形适应被认为仅存在于视觉皮质水平 ,然而本实验室新近实验表明 ,光栅图形适应也存在于正常猫和去视皮质猫的外膝体神经元。本研究目的在于澄清外膝体的图形适应是否来源于视网膜。研究了 79个X和 Y型猫视网膜神经节细胞对长时间的光栅刺激反应。结果显示 :1与外膝体中继细胞不同 ,71 %的神经节细胞对长时间刺激反应不变 ,只有 6%的细胞显示光栅适应 ,而有 2 3%的细胞显示易化作用 ;2上述对长时间的光栅刺激的效应与细胞类型 (X和 Y型或 On-和 Off-中心型 )无关 ;3如同外膝体细胞 ,视网膜神经节细胞的光栅易化作用在刺激后 30 s内结束 ,平均反应幅度上升 1 7% ,其时程符合指数函数 ,平均时间常数为 1 7.7s。本结果提示 ,图形适应可能基本上起源于外膝体 ,而图形易化则起源于视网膜 。

Pattern adaptation is believed to be a unique property of cortical cells.However,recent work in our laboratory has demonstrated grating adaptation of relay cells in the dorsal geniculate nucleus(dLGN) following prolonged exposure to a drifting grating in the normal and cortex ablated cats [1] .The purpose of this study is to test if grating adaptation revealed in the dLGN originates from the retina.We studied the responses of 79 X and Y type ganglion cells in the cat retina to prolonged grating stimuli.In contrast to the dLGN relay cells,neither pattern adaptation nor facilitation was found in the majority of studied cells(71%)in the retina.Only 6% of the cells studied were adapted to the adapting grating,while 23% of the cells studied showed significant facilitation rather than adaptation.There was no significant difference either between X and Y cells or between On center and Off center cells in susceptibility to adapting grating stimuli.The facilitation observed in the retinal ganglion cells completed within 30 s with a mean response increase of 17%,whose time course was well fitted to an exponential function with a mean time constant of 17.7s.The results suggest that the pattern adaptation may essentially originate from the dLGN,while pattern facilitation from the retina.Therefore,the intrageniculate mechanisms may cause the pattern adaptation in the dLGN. [