Rosa M G, Schmid L M
Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Australia.
Exp Brain Res. 1995;102(3):551-6. doi: 10.1007/BF00230660.
The magnification factor (MF) of the stratum griseum superficiale (SGS) of the superior colliculus (SC) was calculated based on visual receptive fields recorded from anaesthetised and paralysed flying foxes (Pteropus spp.). In areal terms, the MF at the representation of central vision was 4-6 times larger than that in the peripheral representation. This variation is less marked than that observed in the primary visual area (V1), but is roughly that expected if the retinotopic map in the SC was defined by the distribution of ganglion cells in the retina. Two measures of the functional spread of activity in the SC, the receptive field images and the point-image size, were calculated. Receptive field images are remarkably similar throughout the SC. As in V1, the point-image size in the SGS of flying foxes is 0.5-0.6 mm and varies little with eccentricity. Bilateral ablation of the visual cortex results in a reduction of the mean receptive field size of neurones in the SGS, and the point-image size is reduced by half. However, the shape of the point-image function is not affected. These results demonstrate that the spread of activity in the SC is nearly constant throughout the retinotopic map and that this is primarily a result of the direct retinal projection. Although the visual cortex has an expanded central representation in comparison with the SC, the corticotectal pathway does not exert a preferential influence on the central representation of the SC.
基于对麻醉和麻痹的狐蝠（Pteropus spp.）记录的视觉感受野，计算了上丘浅层（SGS）的放大因子（MF）。从面积角度来看，中央视觉表征处的MF比周边表征处大4至6倍。这种变化不如在初级视觉区（V1）中观察到的那么明显，但如果上丘中的视网膜拓扑图是由视网膜中神经节细胞的分布定义的，那么这种变化大致是预期的。计算了上丘中活动功能扩散的两个指标，即感受野图像和点图像大小。整个上丘的感受野图像非常相似。与V1一样，狐蝠SGS中的点图像大小为0.5 - 0.6毫米，并且随离心率变化不大。双侧视觉皮层切除导致SGS中神经元的平均感受野大小减小，点图像大小减半。然而，点图像函数的形状不受影响。这些结果表明，上丘中活动的扩散在整个视网膜拓扑图中几乎是恒定的，这主要是直接视网膜投射的结果。尽管与上丘相比，视觉皮层有扩大的中央表征，但皮质 - 上丘通路对上丘的中央表征没有施加优先影响。
