Sandstrom C K, Krishnan S, Slavin M J, Tran T-T T, Doraiswamy P M, Petrella J R
Department of Radiology, Brain Imaging and Analysis Center, Duke University Medical Center, Durham, NC, USA.
AJNR Am J Neuroradiol. 2006 Sep;27(8):1622-7.
Functional MR imaging has been used to study patterns of hippocampal activation that distinguish pathologic from normal memory loss in the elderly population. Our objective was to assess whether hippocampal atrophy confounds measurements of hippocampal activation in subjects with mild cognitive impairment (MCI).
Twenty subjects with MCI and 20 elderly control subjects with objectively normal memory were studied at 4T during a face-name paradigm designed to activate the hippocampus. Hippocampal activation was measured using 2 separate approaches: applying a preset region of interest (ROI) in standardized template space and applying a manually drawn ROI in native subject space. Pearson correlation coefficients were calculated to compare group-dependent relationships between hippocampal volume and activation. Analysis of covariance (ANCOVA) was performed to assess group differences in hippocampal activation during encoding and retrieval. Age and hippocampal volume were included as covariates, as was a term for the interaction between hippocampal volume and group.
When hippocampal activation was measured by the template-based method, the correlation coefficient in the right hippocampus of subjects with MCI but not control subjects during retrieval differed significantly from zero. There was a significant (P < .05) group-by-volume interaction in the ANCOVA model. No significant correlations or interactions were demonstrated when activation was measured in native subject space with manually drawn ROIs.
Our findings suggest a potential confounding relationship between hippocampal volume and activation for subjects with MCI in template-based analyses. Template-based measures of hippocampal activation that do not adequately account for hippocampal atrophy should be used with caution in patients with MCI.
功能磁共振成像已被用于研究海马激活模式，以区分老年人群中病理性记忆丧失与正常记忆丧失。我们的目的是评估海马萎缩是否会混淆轻度认知障碍（MCI）患者海马激活的测量结果。
20名MCI患者和20名客观记忆正常的老年对照者在4T磁场下接受研究，采用面孔-名字范式激活海马。使用两种不同方法测量海马激活：在标准化模板空间中应用预设感兴趣区域（ROI），以及在受试者原生空间中手动绘制ROI。计算Pearson相关系数以比较海马体积与激活之间的组间依赖关系。进行协方差分析（ANCOVA）以评估编码和检索过程中海马激活的组间差异。将年龄和海马体积作为协变量纳入，还纳入了海马体积与组间相互作用的一项。
当通过基于模板的方法测量海马激活时，MCI患者右侧海马在检索过程中的相关系数与零有显著差异，而对照者无此差异。在ANCOVA模型中存在显著的（P <.05）体积×组间相互作用。当使用手动绘制ROI在受试者原生空间中测量激活时，未显示出显著的相关性或相互作用。
我们的研究结果表明，在基于模板的分析中，MCI患者的海马体积与激活之间可能存在混杂关系。对于MCI患者，在未充分考虑海马萎缩的情况下，基于模板的海马激活测量应谨慎使用。
