Ahmad Kareem M, Klug Karl, Herr Steve, Sterling Peter, Schein Stan
Department of Psychology, Franz Hall, UCLA, Los Angeles 90095-1563, USA.
Vis Neurosci. 2003 Mar-Apr;20(2):189-209. doi: 10.1017/s0952523803202091.
We examine the assumptions that the fovea contains equal numbers of inner (invaginating or ON) and outer (flat or OFF) midget bipolar cells and equal numbers of inner and outer diffuse bipolar cells. Based on reconstruction from electron photomicrographs of serial thin sections through the fovea of a macaque monkey, we reject both assumptions. First, every foveal L and M cone is presynaptic to one inner and one outer midget bipolar cell; however, S cones are presynaptic to one outer but no inner midget bipolar cell. Second, we measure the density of all foveal cells in the same patch of fovea, affording accurate cell density ratios. For each foveal cone pedicle, at a density of 26,500 mm(-2), there is close to one (0.88) outer diffuse bipolar cell but only 0.40 inner diffuse bipolar cells. This asymmetry may be related to differences in resolution and sensitivity for light increments and decrements. We also find one (1.01) Müller cell, one (1.01) amacrine cell in the inner nuclear layer, and close to one (0.83) horizontal cell for each cone pedicle. In addition, for each S cone, there are two inner S-cone bipolar cells and two small bistratified ganglion cells. In total, there are 3.4 cone bipolar cells per cone but only 2.6 ganglion cells per cone. The latter ratio is enough to accommodate one midget ganglion cell for each midget bipolar cell.
中央凹内的内（内陷或ON）侏儒双极细胞和外（扁平或OFF）侏儒双极细胞数量相等，内、外弥散双极细胞数量也相等。基于对猕猴中央凹连续薄切片的电子显微照片进行的重建，我们否定了这两个假设。首先，每个中央凹的L和M视锥细胞都与一个内侏儒双极细胞和一个外侏儒双极细胞形成突触；然而，S视锥细胞仅与一个外侏儒双极细胞形成突触，而不与任何内侏儒双极细胞形成突触。其次，我们测量了中央凹同一区域内所有细胞的密度，得出了准确的细胞密度比。对于每个中央凹视锥细胞蒂，密度为26,500 mm(-2)时，有近一个（0.88）外弥散双极细胞，但只有0.40个内弥散双极细胞。这种不对称可能与光增量和减量的分辨率及敏感度差异有关。我们还发现，每个视锥细胞蒂有一个（1.01）米勒细胞、一个（1.01）内核层无长突细胞和近一个（0.83）水平细胞。此外，对于每个S视锥细胞，有两个内S视锥双极细胞和两个小双分层神经节细胞。每个视锥细胞共有3.4个视锥双极细胞，但每个视锥细胞只有2.6个神经节细胞。后一比例足以容纳每个侏儒双极细胞对应的一个侏儒神经节细胞。
