中央和旁中央视野到人类视觉皮层的二维映射。
Two-dimensional mapping of the central and parafoveal visual field to human visual cortex.
作者信息
Schira Mark M, Wade Alex R, Tyler Christopher W
机构信息
Smith-Kettlewell Eye Research Institute, 2318 Fillmore St., San Francisco, CA 94115, USA.
出版信息
J Neurophysiol. 2007 Jun;97(6):4284-95. doi: 10.1152/jn.00972.2006. Epub 2007 Mar 14.
Primate visual cortex contains a set of maps of visual space. These maps are fundamental to early visual processing, yet their form is not fully understood in humans. This is especially true for the central and most important part of the visual field--the fovea. We used functional magnetic resonance imaging (fMRI) to measure the mapping geometry of human V1 and V2 down to 0.5 degrees of eccentricity. By applying automated atlas fitting procedures to parametrize and average retinotopic measurements of eight brains, we provide a reference standard for the two-dimensional geometry of human early visual cortex of unprecedented precision and analyze this high-quality mean dataset with respect to the 2-dimensional cortical magnification morphometry. The analysis indicates that 1) area V1 has meridional isotropy in areal projection: equal areas of visual space are mapped to equal areas of cortex at any given eccentricity. 2) V1 has a systematic pattern of local anisotropies: cortical magnification varies between isopolar and isoeccentricity lines, and 3) the shape of V1 deviates systematically from the complex-log model, the fit of which is particularly poor close to the fovea. We therefore propose that human V1 be fitted by models based on an equal-area principle of its two-dimensional magnification. 4) V2 is elongated by a factor of 2 in eccentricity direction relative to V1 and has significantly more local anisotropy. We propose that V2 has systematic intrinsic curvature, but V1 is intrinsically flat.
灵长类动物的视觉皮层包含一组视觉空间图谱。这些图谱是早期视觉处理的基础,但在人类中其形式尚未完全被理解。对于视野的中央且最重要的部分——中央凹而言尤其如此。我们使用功能磁共振成像(fMRI)来测量人类V1和V2在低至0.5度偏心率下的映射几何结构。通过应用自动图谱拟合程序对八个大脑的视网膜拓扑测量进行参数化和平均,我们提供了一个前所未有的高精度的人类早期视觉皮层二维几何结构的参考标准,并针对二维皮质放大形态测量分析了这个高质量的平均数据集。分析表明:1)V1区域在区域投影上具有子午线各向同性:在任何给定偏心率下,相等面积的视觉空间被映射到相等面积的皮层。2)V1具有局部各向异性的系统模式:皮质放大率在等极线和等偏心率线之间变化,并且3)V1的形状系统地偏离复对数模型,在中央凹附近其拟合尤其差。因此,我们建议用基于其二维放大率等面积原理的模型来拟合人类V1。4)相对于V1,V2在偏心率方向上拉长了2倍,并且具有明显更多的局部各向异性。我们提出V2具有系统的固有曲率,但V1本质上是平坦的。