Rosa M G, Fritsches K A, Elston G N
Vision, Touch & Hearing Research Centre, Department of Physiology and Pharmacology, The University of Queensland, Australia.
J Comp Neurol. 1997 Nov 3;387(4):547-67. doi: 10.1002/(sici)1096-9861(19971103)387:4<547::aid-cne6>3.0.co;2-2.
The organisation of the second visual area (V2) in marmoset monkeys was studied by means of extracellular recordings of responses to visual stimulation and examination of myelin- and cytochrome oxidase-stained sections. Area V2 forms a continuous cortical belt of variable width (1-2 mm adjacent to the foveal representation of V1, and 3-3.5 mm near the midline and on the tentorial surface) bordering V1 on the lateral, dorsal, medial, and tentorial surfaces of the occipital lobe. The total surface area of V2 is approximately 100 mm2, or about 50% of the surface area of V1 in the same individuals. In each hemisphere, the receptive fields of V2 neurones cover the entire contralateral visual hemifield, forming an ordered visuotopic representation. As in other simians, the dorsal and ventral halves of V2 represent the lower and upper contralateral quadrants, respectively, with little invasion of the ipsilateral hemifield. The representation of the vertical meridian forms the caudal border of V2, with V1, whereas a field discontinuity approximately coincident with the horizontal meridian forms the rostral border of V2, with other visually responsive areas. The bridge of cortex connecting dorsal and ventral V2 contains neurones with receptive fields centred within 1 degree of the centre of the fovea. The visuotopy, size, shape and location of V2 show little variation among individuals. Analysis of cortical magnification factor (CMF) revealed that the V2 map of the visual field is highly anisotropic: for any given eccentricity, the CMF is approximately twice as large in the dimension parallel to the V1/V2 border as it is perpendicular to this border. Moreover, comparison of V2 and V1 in the same individuals demonstrated that the representation of the central visual field is emphasised in V2, relative to V1. Approximately half of the surface area of V2 is dedicated to the representation of the central 5 degrees of the visual field. Calculations based on the CMF, receptive field scatter, and receptive field size revealed that the point-image size measured parallel to the V1/V2 border (2-3 mm) equals the width of a full cycle of cytochrome oxidase stripes in V2, suggesting a close correspondence between physiological and anatomical estimates of the dimensions of modular components in this area.
通过对视觉刺激反应的细胞外记录以及对髓鞘和细胞色素氧化酶染色切片的检查，研究了狨猴第二视区（V2）的组织结构。V2区在枕叶的外侧、背侧、内侧和小脑幕表面形成一条宽度可变的连续皮质带（在V1中央凹代表区附近为1 - 2毫米，在中线附近和小脑幕表面为3 - 3.5毫米），与V1区相邻。V2区的总表面积约为100平方毫米，约占同个体V1区表面积的50%。在每个半球中，V2神经元的感受野覆盖整个对侧视觉半视野，形成有序的视拓扑表征。与其他灵长类动物一样，V2区的背侧和腹侧分别代表对侧下半象限和上半象限，同侧半视野的侵入较少。垂直子午线的表征在V2区与V1区形成尾侧边界，而与水平子午线大致重合的视野间断则在V2区与其他视觉反应区形成头侧边界。连接V2区背侧和腹侧的皮质桥包含感受野以中央凹中心1度范围内为中心的神经元。V2区的视拓扑、大小、形状和位置在个体之间变化很小。皮质放大因子（CMF）分析表明，V2区的视野图谱高度各向异性：对于任何给定的偏心率，与V1/V2边界平行方向的CMF约为垂直于该边界方向的两倍。此外，对同个体的V2区和V1区进行比较表明，相对于V1区，V2区更强调中央视野的表征。V2区约一半的表面积用于代表中央5度的视野。基于CMF、感受野离散度和感受野大小的计算表明，平行于V1/V2边界测量的点图像大小（2 - 3毫米）等于V2区细胞色素氧化酶条纹一个完整周期的宽度，这表明该区域模块化组件尺寸的生理和解剖学估计之间存在密切对应关系。
