Heggelund P, Krekling S, Skottun B C
J Physiol. 1984 Jul;352:327-37. doi: 10.1113/jphysiol.1984.sp015294.
Spatial summation along the optimum stimulus orientation in subregions of simple-cell receptive fields in cat striate cortex was studied quantitatively by measuring the response to stationary light slits of variable length. Before summation analysis, the cell's discharge field was mapped by flashing a test slit on and off in a sequence of positions through the receptive field. A static activation procedure was used to determine the extension of subregions of the receptive field where light stimulation increased (enhancement) or decreased (suppression) the firing rate. An activation slit in the optimum orientation was positioned in the most responsive position of the discharge field and the effects of a parallel test slit, in a series of broadside positions, were assessed from the changes induced in the discharge elicited by the activation slit. Length-response curves for on and off responses were made by positioning a test slit in the respective subregions of the discharge field. The activation procedure was used to make length-response curves for suppression. A test slit of variable length was positioned in a suppression region defined by the activation profiles and an activation slit of fixed length was centred in the most responsive discharge field position. Length summation was found for all cells, both with respect to on and off responses, and suppression. The curves for on and off responses had a maximum value beyond which the response declined or levelled off, but some cells had a secondary, more shallow increase beyond an initial, steeply rising part. Similar properties were found for summation of suppression except that the effects were opposite in sign. Curves made for both on and off regions in the same cell often differed in shape. Such differences were also found when length-response curves made in different suppression regions of the same cell were compared. The various length-summation functions were explained by a model presuming that simple-cell receptive fields consist of partially overlapping non-concentric excitatory and inhibitory fields. This arrangement would also explain why length-response curves in various subregions often had different shapes.
通过测量对不同长度静止光缝的反应，对猫纹状皮层简单细胞感受野子区域中沿最佳刺激方向的空间总和进行了定量研究。在总和分析之前，通过在感受野的一系列位置上闪烁测试光缝来绘制细胞的放电场。使用静态激活程序来确定感受野子区域的范围，在该范围内光刺激会增加（增强）或降低（抑制）放电率。将处于最佳方向的激活光缝置于放电场的最敏感位置，并根据激活光缝引起的放电变化评估一系列侧面位置的平行测试光缝的影响。通过将测试光缝置于放电场的各个子区域来绘制开反应和关反应的长度-反应曲线。使用激活程序来绘制抑制的长度-反应曲线。将可变长度的测试光缝置于由激活轮廓定义的抑制区域中，并将固定长度的激活光缝置于最敏感的放电场位置中心。发现所有细胞在开反应、关反应和抑制方面都存在长度总和现象。开反应和关反应的曲线都有一个最大值，超过该值反应会下降或趋于平稳，但一些细胞在初始陡峭上升部分之后有一个次要的、更平缓的增加。抑制总和也发现了类似的特性，只是效果的符号相反。同一细胞的开区域和关区域绘制的曲线形状通常不同。当比较同一细胞不同抑制区域绘制的长度-反应曲线时也发现了这种差异。各种长度总和函数由一个模型解释，该模型假定简单细胞感受野由部分重叠的非同心兴奋性和抑制性场组成。这种排列也可以解释为什么不同子区域的长度-反应曲线通常具有不同的形状。
