目的·为大脑皮层表面形态的表达和定量描述提出一种基于地学的理论方法。方法·从阿尔茨海默病神经成像倡议（Alzheimer′s Disease Neuroimaging Initiative，ADNI）数据库下载85个正常认知（normal cognition，NC）样本和84个阿尔茨海默病（Alzheimer′s disease，AD）样本作为研究对象，使用SPM 12软件包，提取脑磁共振成像（magnetic resonance imaging，MRI）影像的大脑皮层数据。将起伏的大脑皮层影像映射为三维重建后的点云数据，并根据数字地形分析的理论方法，进一步构建大脑数字高程模型（digital elevation model，DEM），实现对大脑皮层形态的数字化表达。引入地学中的粗糙度、起伏度、高程等地形因子指标，用于定量描述大脑皮层的形态特征。以年龄为协变量进行协方差分析；再分别根据性别分组，以NC组与AD组为变量；根据地形因子分组，以左右半脑为变量，进行独立样本t检验，揭示大脑皮层形态的变化规律。结果·大脑皮层粗糙度、起伏度与皮层厚度数值随年龄增长呈线性分布，且AD组与NC组各指标间差异均具有统计学意义（均P<0.05）；男性和女性的粗糙度和起伏度指标均表现出AD组大于NC组（均P<0.05），皮层厚度表现出AD组小于NC组（P=0.000），高程则只在女性中具备组间差异（P=0.043）；NC组的左半脑粗糙度、起伏度与高程数值均大于右半脑（均P<0.05），AD则只在高程指标中具备组间差异（P=0.000）。结论·地形因子指标能够显著区分AD与NC患者间大脑皮层的差异，并且在以年龄、性别和左右半脑作为变量时，有较好的区分表现，有望为医学量化大脑皮层形态提供辅助手段。

Objective ·To propose a theoretical method based on geosciences for the expression and quantitative description of the surface morphology of the cerebral cortex. Methods ·Eighty-five samples of normal cognition (NC) and 84 samples of Alzheimer′s disease (AD) were downloaded from the Alzheimer′s Disease Neuroimaging Initiative (ADNI) database, and the cerebral cortex data of magnetic resonance imaging (MRI) images of the human brain were extracted by using SPM 12 software package. The undulating cerebral cortex image was mapped into the point cloud data after three-dimensional reconstruction, and the digital elevation model (DEM) of the brain was further constructed according to the theoretical method of digital terrain analysis to realize the digital expression of the cerebral cortex morphology. The study introduced terrain factors′ indicators such as roughness, relief amplitude and elevation in geoscience to quantitatively describe the morphological characteristics of the cerebral cortex. Covariance analysis was conducted with age as the covariate, and independent sample t test was conducted with gender into groups and NC samples and AD samples as the variables, terrain factors as the group and left and right hemispheres as the variables to reveal the change rule of cerebral cortex morphology. Results ·The roughness, relief amplitude and thickness of the cerebral cortex were linearly distributed with age, and the differences between the AD group and the NC group were all statistically significant (all P<0.05); the roughness and relief amplitude of both men and women showed that the AD group was larger than the NC group (both P<0.05), the cortical thickness showed that the AD group was smaller than the NC group (P=0.000), and the elevation only had an inter-group difference in women (P=0.043); the left hemisphere roughness, relief amplitude and elevation values of NC group were higher than those of the right hemisphere (all P<0.05), while AD only had inter-group differences in elevation indicators (P=0.000). Conclusion ·Terrain factors can significantly distinguish the cerebral cortex differences between AD and NC patients, and has a good distinction when age, gender and left and right hemisphere are used as variables. It is expected to provide an auxiliary means for the medical quantification of cerebral cortex morphology.