Estimating linear cortical magnification in human primary visual cortex via dynamic programming
Estimating linear cortical magnification in human primary visual cortex via dynamic programming
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DOI：
10.1016/j.neuroimage.2005.11.049
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发表时间：
2006-05-15
期刊：
影响因子：
5.7
通讯作者：
Miller, Michael I.
中科院分区：
文献类型：
--
作者：
Qiu, Anqi;Rosenau, Benjamin J.;Miller, Michael I.
人类初级视觉皮层是视网膜定位组织的，皮层中的相邻位置代表视网膜上的相邻位置。皮层中的空间采样是高度不均匀的：视网膜单位面积的皮层数量随着视网膜偏心率的增加而减少。这种采样特性可以通过线性皮层放大因子来量化，线性皮层放大因子以每度视角的皮层毫米数表示。在本文中，我们提出了一种新的方法，使用动态规划和fMRI视网膜偏心映射估计的线性皮层放大因子在人类初级视觉皮层（VI）。我们定位皮质活动，而受试者观看七个固定的对比度反转径向棋盘环的厚度相等，平铺视野从1.62到12.96度的偏心。每个环的所有时期的成像数据与每个受试者的固定时期的数据进行对比。然后将所得的t统计图叠加在由每个个体受试者枕叶的灰/白色物质边界表面构建的局部坐标系上，分别针对每个环。平滑的地图上的皮质表面上的功能活动的拉普拉斯-贝尔特拉米算子，将皮质表面的几何形状的正交基。这使我们能够通过对皮质表面上所有可能路径的动态编程优化，稳定地跟踪每个环引起的最大激活脊。我们估计的线性皮质放大因子，通过计算的测地线之间的距离在五个正常受试者的人口皮质表面上的激活脊。通过比较基于一个象限数据的结果与基于完整半野沿着数据的结果以及分半可靠性分析，评估这些估计值的可靠性。(c)2005年爱思唯尔公司All rights reserved.
Human primary visual cortex is organized retinotopically, with adjacent locations in cortex representing adjacent locations on the retina. The spatial sampling in cortex is highly nonuniform: the amount of cortex devoted to a unit area of retina decreases with increasing retinal eccentricity. This sampling property can be quantified by the linear cortical magnification factor, which is expressed in terms of millimeters of cortex per degree of visual angle. In this paper, we present a new method using dynamic programming and fMRI retinotopic eccentricity mapping to estimate the linear cortical magnification factor in human primary visual cortex (VI). We localized cortical activity while subjects viewed each of seven stationary contrast-reversing radial checkerboard rings of equal thickness that tiled the visual field from 1.62 to 12.96 degrees of eccentricity. Imaging data from all epochs of each ring were contrasted with data from fixation epochs on a subject-by-subject basis. The resulting t statistic maps were then superimposed on a local coordinate system constructed from the gray/white matter boundary surface of each individual subject's occipital lobe, separately for each ring. Smoothed maps of functional activity on the cortical surface were constructed using orthonormal bases of the Laplace-Beltrami operator that incorporate the geometry of the cortical surface. This allowed us to stably track the ridge of maximum activation due to each ring via dynamic programming optimization over all possible paths on the cortical surface. We estimated the linear cortical magnification factor by calculating geodesic distances between activation ridges on the cortical surface in a population of five normal subjects. The reliability of these estimates was assessed by comparing results based on data from one quadrant to those based on data from the full hemifield along with a split-half reliability analysis. (c) 2005 Elsevier Inc. All rights reserved.