Sieving P A, Steinberg R H
J Neurophysiol. 1987 Jan;57(1):104-20. doi: 10.1152/jn.1987.57.1.104.
We investigated the retinal depth of origin of the pattern ERG (PERG) in cat by recording extracellular responses to contrast reversal grating stimuli and performing a current source-density analysis of the depth profiles. The local ERG (LERG) was recorded within the retina; the waveform varied with grating spatial phase position of the microelectrode. The LERG at any arbitrary single spatial phase was not equivalent to the corneal PERG. To obtain an "intraretinal PERG" equivalent to the corneal PERG, we summed LERGs from many spatial phases over a complete grating cycle. This intraretinal PERG was analogous to the corneal PERG in having only even harmonic components and also in being independent of the grating spatial phase. The absence of the fundamental and odd harmonics appeared to result from the summation of responses across grating spatial phase rather than from an intrinsic generator mechanism. The spatial contrast sensitivity function for the intraretinal PERG at 8 Hz was tuned, with peak sensitivity between 0.5 and 0.75 cycles per degree in the area centralis. The 8-Hz PERG response was maximum in the proximal retina at approximately 23% depth from the internal limiting membrane (ILM). This depth lies within the inner plexiform layer and is proximal to the depth at which the b-wave was maximum (49-61% depth). PERG and flash-elicited ERG responses exhibited different amplitude profiles as a function of retinal depth. Analysis of the 8-Hz PERG depth profiles identified generators in the proximal retina between the ILM and the inner plexiform-inner nuclear boundary. The analysis suggested that at least two generators were present. The proportional contribution to the corneal PERG from each of the two or more proximal generators was not determined. Contributions to the corneal PERG from more distal generators, however, were not specifically excluded. The intraretinal recordings suggest that under some conditions contrast reversal gratings at 8 Hz can elicit current generators in the proximal retina of cat. These generators appear to respond to local retinal illumination, and the intraretinal PERG results from nonlinear elements of at least two generators. Spatial tuning of the intraretinal PERG may reflect properties of the underlying LERG components, including the M-wave.
我们通过记录对对比度反转光栅刺激的细胞外反应并对深度分布进行电流源密度分析，研究了猫视网膜中图形视网膜电图（PERG）的起源深度。在视网膜内记录局部视网膜电图（LERG）；其波形随微电极的光栅空间相位位置而变化。任意单个空间相位处的LERG都不等同于角膜PERG。为了获得等同于角膜PERG的“视网膜内PERG”，我们在一个完整的光栅周期内对多个空间相位的LERG进行求和。这种视网膜内PERG类似于角膜PERG，仅具有偶次谐波成分，并且也与光栅空间相位无关。基波和奇次谐波的缺失似乎是由于跨光栅空间相位的反应求和所致，而非源于内在的发生器机制。8Hz时视网膜内PERG的空间对比敏感度函数是调谐的，在中央凹区域每度0.5至0.75周期之间具有峰值敏感度。8Hz的PERG反应在距内界膜（ILM）约23%深度的视网膜近端最大。该深度位于内网状层内，且比b波最大时的深度（49 - 61%深度）更靠近近端。PERG和闪光诱发的视网膜电图反应作为视网膜深度的函数表现出不同的振幅分布。对8Hz PERG深度分布的分析确定了ILM和内网状层 - 内核边界之间视网膜近端的发生器。分析表明至少存在两个发生器。未确定两个或更多近端发生器对角膜PERG的比例贡献。然而，并未明确排除更远端发生器对角膜PERG的贡献。视网膜内记录表明，在某些条件下，8Hz的对比度反转光栅可在猫的视网膜近端诱发电流发生器。这些发生器似乎对局部视网膜光照有反应，并且视网膜内PERG由至少两个发生器的非线性元件产生。视网膜内PERG的空间调谐可能反映了潜在LERG成分（包括M波）的特性。
