Heggelund P, Krekling S, Skottun B C
Exp Brain Res. 1983;52(1):87-98. doi: 10.1007/BF00237153.
Spatial summation was studied quantitatively through width response curves made with an optimally oriented test slit of variable width, and by comparing the response to combined presentation of several parallel slits with the response to each slit alone. Prior to summation analysis, the cell's discharge field (DF) was mapped by presenting a test slit ON and OFF across the receptive field. Activation profiles, showing the extension of subregions where light stimulation increased (enhancement) or decreased the firing rate (suppression), were made by presenting an optimally oriented activation slit in the most responsive DF-position. Against this activity the effects of a parallel test slit were determined in a series of broadside positions. Width response curves were made over the subregions of the DF and the activation profiles. Spatial summation was found in all cells, but the width of the summation region was smaller than the width of the subregions in the respective profiles. The width of the summation region was related to the degree of activation rather than to specific locations within the receptive field. The effect produced by several slits presented together deviated from the algebraic sum of the effects produced by each slit alone. Linear summation was rarely found. Accumulated response curves obtained by integration of DF or activation profiles were compared with width response curves to test linearity of summation. Linear summation throughout the whole receptive field was never found. A satisfactory fit was found only over a narrow region showing that summation was linear within a small part of the summation region. Linearity ended near response maxima or minima in the response profiles. The results indicate that the receptive field of simple cells consists of overlapping excitatory and inhibitory fields, and that the exact location and width of enhancement and suppression zones are determined by an activity-dependent balance between excitatory and inhibitory inputs.
通过使用宽度可变的最佳取向测试狭缝制作宽度响应曲线，并将多个平行狭缝组合呈现的响应与每个狭缝单独呈现的响应进行比较，对空间总和进行了定量研究。在总和分析之前，通过在感受野上呈现测试狭缝的开和关来绘制细胞的放电场（DF）。通过在最敏感的DF位置呈现最佳取向的激活狭缝，制作激活轮廓，显示光刺激增加（增强）或降低放电率（抑制）的子区域的扩展。针对这种活动，在一系列侧面位置确定平行测试狭缝的效果。在DF的子区域和激活轮廓上制作宽度响应曲线。在所有细胞中都发现了空间总和，但总和区域的宽度小于相应轮廓中子区域的宽度。总和区域的宽度与激活程度有关，而不是与感受野内的特定位置有关。几个狭缝一起呈现产生的效果偏离了每个狭缝单独产生的效果的代数和。很少发现线性总和。将通过DF或激活轮廓积分获得的累积响应曲线与宽度响应曲线进行比较，以测试总和的线性度。在整个感受野中从未发现线性总和。仅在一个狭窄区域发现了令人满意的拟合，表明在总和区域的一小部分内总和是线性的。线性在响应轮廓中的响应最大值或最小值附近结束。结果表明，简单细胞的感受野由重叠的兴奋性和抑制性场组成，增强和抑制区的确切位置和宽度由兴奋性和抑制性输入之间的活动依赖性平衡决定。
