Irvin G E, Casagrande V A, Norton T T
Department of Physiological Optics, School of Optometry, University of Alabama, Birmingham 35294-4390.
Vis Neurosci. 1993 Mar-Apr;10(2):363-73. doi: 10.1017/s0952523800003758.
As in other primates, the lateral geniculate nucleus (LGN) of the prosimian primate, bush baby (Galago crassicaudatus), contains three morphologically and physiologically distinct cell classes [magnocellular (M), parvocellular (P), and koniocellular (K)] (Norton & Casagrande, 1982; Casagrande & Norton, 1991). The present study examined quantitatively the center/surround relationships of cells in all three classes. Estimates of receptive-field center size (Rc) and sensitivity (Kc) and of surround size (Rs) and sensitivity (Ks) were obtained from 47 LGN relay cells by fitting a difference of Gaussians function to contrast-sensitivity data. For M and P cells, center size (Rc) increases with eccentricity but is about two times larger for M than for P cells at a given eccentricity. Surround size (Rs) increases with eccentricity for P but not for M or K cells. The center sensitivity (Kc) is inversely related to center size (Rc) and surround sensitivity (Ks) is inversely related to surround size (Rs) for cells in all classes, a result consistent with the sensitivity regulation that is produced by light adaptation. High spatial-frequency cutoff (acuity) is inversely related to center size (Rc). However, the peak contrast sensitivity is relatively independent of Rc. The ratio of the integrated strength (volume) of the surround to the volume of the center remains relatively constant (median, 0.87) across all three cell classes. This ratio is an excellent predictor of a cell's rolloff in contrast sensitivity at low spatial frequencies: cells with a low surround/center ratio have less low-frequency rolloff. Although M, P, and K cells generally display similar center/surround relationships, differences in center size and the other parameters between the classes distinguish most M, P, and K cells. These findings demonstrate that both similarities and differences in the visual-response properties of primate LGN cells in these three parallel afferent pathways can be explained by basic center/surround relationships.
与其他灵长类动物一样，原猴亚目灵长类动物婴猴（粗尾婴猴，Galago crassicaudatus）的外侧膝状体核（LGN）包含三种在形态和生理上截然不同的细胞类型[大细胞（M）、小细胞（P）和 koniocellular 细胞（K）]（诺顿和卡萨格兰德，1982 年；卡萨格兰德和诺顿，1991 年）。本研究定量检查了所有这三种细胞类型的细胞的中心/周边关系。通过将高斯函数差异拟合到对比敏感度数据，从 47 个 LGN 中继细胞中获得了感受野中心大小（Rc）和敏感度（Kc）以及周边大小（Rs）和敏感度（Ks）的估计值。对于 M 细胞和 P 细胞，中心大小（Rc）随离心率增加，但在给定离心率下，M 细胞的中心大小比 P 细胞大约两倍。对于 P 细胞，周边大小（Rs）随离心率增加，而 M 细胞或 K 细胞则不然。所有细胞类型的中心敏感度（Kc）与中心大小（Rc）呈负相关，周边敏感度（Ks）与周边大小（Rs）呈负相关，这一结果与光适应产生的敏感度调节一致。高空间频率截止（敏锐度）与中心大小（Rc）呈负相关。然而，峰值对比敏感度相对独立于 Rc。在所有三种细胞类型中，周边的积分强度（体积）与中心体积的比率保持相对恒定（中位数为 0.87）。该比率是细胞在低空间频率下对比敏感度下降的出色预测指标：周边/中心比率低的细胞低频下降较少。尽管 M、P 和 K 细胞通常表现出相似的中心/周边关系，但这些细胞类型之间在中心大小和其他参数上的差异区分了大多数 M、P 和 K 细胞。这些发现表明，这三条平行传入通路中灵长类动物 LGN 细胞视觉反应特性的相似性和差异都可以通过基本的中心/周边关系来解释。
