Salmond C H, Ashburner J, Vargha-Khadem F, Connelly A, Gadian D G, Friston K J
Developmental Cognitive Neuroscience Unit, Institute of Child Health, University College London, 30 Guilford Street, London WCIN 1EM, United Kingdom.
Neuroimage. 2002 Sep;17(1):507-12. doi: 10.1006/nimg.2002.1191.
We investigated the accuracy of spatial basis function normalization using anatomical landmarks to determine how precisely homologous regions are colocalized. We examined precision in terms of: (1) the number of nonlinear basis functions used by the normalization procedure; (2) the degree of (Bayesian) regularization; and (3) the effect of substituting different templates and how this interacted with the number of basis functions. The face validity of spatial normalization was assessed as a function of these parameters, using the colocalization of homologous landmarks in a test sample of 20 normally developing children and 5 children with bilateral hippocampal pathology. Our results suggest that when optimal normalization parameters are used, anatomical landmarks in the medial temporal lobes are colocalized to within a standard deviation of about 1 mm. When suboptimal parameters are used this standard deviation can increase up to 3 mm. Interestingly the optimal parameters are those that provide a rather constrained normalization as opposed to those that optimize intensity matching at the expense of rendering the warps "unlikely." The implications of our results, for users of voxel-based morphometry, are discussed.
我们研究了使用解剖学标志点进行空间基函数归一化的准确性，以确定同源区域的共定位精度。我们从以下几个方面考察了精度：（1）归一化过程中使用的非线性基函数数量；（2）（贝叶斯）正则化程度；（3）替换不同模板的效果以及这与基函数数量的相互作用。利用20名正常发育儿童和5名双侧海马病变儿童的测试样本中同源标志点的共定位情况，将空间归一化的表面效度评估为这些参数的函数。我们的结果表明，当使用最佳归一化参数时，内侧颞叶的解剖学标志点共定位在约1毫米的标准差范围内。当使用次优参数时，该标准差可增加至3毫米。有趣的是，最佳参数是那些提供相当受限归一化的参数，而不是那些以使变形“不太可能”为代价优化强度匹配的参数。我们讨论了研究结果对基于体素的形态计量学用户的意义。
