Rosa M G, Schmid L M, Krubitzer L A, Pettigrew J D
Department of Physiology and Pharmacology, University of Queensland, St. Lucia, Australia.
J Comp Neurol. 1993 Sep 1;335(1):55-72. doi: 10.1002/cne.903350105.
The representation of the visual field in the occipital cortex was studied by multiunit recordings in seven flying foxes (Pteropus spp.), anesthetized with thiopentone/N2O and immobilized with pancuronium bromide. On the basis of its visuotopic organization and architecture, the primary visual area (V1) was distinguished from neighboring areas. Area V1 occupies the dorsal surface of the occipital pole, as well as most of the tentorial surface of the cortex, the posterior third of the mesial surface of the brain, and the upper bank of the posterior portion of the splenial sulcus. In each hemisphere, it contains a precise, visuotopically organized representation of the entire extent of the contralateral visual hemifield. The representation of the vertical meridian, together with 8-15 degrees of ipsilateral hemifield, forms the anterior border of V1 with other visually responsive areas. The representation of the horizontal meridian runs anterolateral to posteromedial, dividing V1 so that the lower visual quadrant is represented medially, and the upper quadrant laterally. The total surface area of V1 is about 140 mm2 for P. poliocephalus, and 110 mm2 for P. scapulatus. The representation of the central visual field is greatly magnified relative to that of the periphery. The cortical magnification factor decreases with increasing eccentricity, following a negative power function. Conversely, receptive field sizes increase markedly with increasing eccentricity, and therefore the point-image size is approximately constant throughout V1. The emphasis in the representation of the area centralis in V1 is much larger than that expected on the basis of ganglion cell counts in flat-mounted retinas. Thus, a larger degree of convergence occurs at the peripheral representations in the retino-geniculo-cortical pathway, in comparison with the central representations. The marked emphasis in the representation of central vision, the wide extent of the binocular field of vision, and the relatively large surface area of V1 reflect the importance of vision in megachiropterans.
通过对7只被硫喷妥钠/一氧化二氮麻醉并用泮库溴铵固定的狐蝠（狐蝠属）进行多单位记录，研究了枕叶皮质中视野的表征。根据其视拓扑组织和结构，将初级视觉区（V1）与相邻区域区分开来。V1区占据枕极的背表面，以及皮质的大部分小脑幕表面、大脑内侧表面的后三分之一，和胼胝体沟后部的上缘。在每个半球中，它包含对侧视觉半视野整个范围的精确视拓扑组织表征。垂直子午线的表征，连同同侧半视野的8 - 15度，形成V1与其他视觉反应区域的前边界。水平子午线的表征从前外侧向后内侧延伸，并将V1区分开，使得下视觉象限在内侧表征，上象限在外侧表征。对于灰头狐蝠，V1区的总表面积约为140平方毫米，对于肩章狐蝠为110平方毫米。相对于周边区域，中央视野的表征被极大地放大。皮质放大因子随着离心率增加而降低，遵循负幂函数。相反，感受野大小随着离心率增加而显著增大，因此在整个V1区点图像大小大致恒定。V1区中中央凹表征的重点比基于扁平视网膜中神经节细胞计数预期的要大得多。因此，与中央表征相比，在视网膜 - 膝状体 - 皮质通路的周边表征处发生了更大程度的会聚。中央视觉表征的显著重点、双目视野的广泛范围以及V1区相对较大的表面积反映了视觉在大蝙蝠中的重要性。
