Branco Daniel M, Suarez Ralph O, Whalen Stephen, O'Shea James P, Nelson Aaron P, da Costa Jaderson C, Golby Alexandra J
Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Neuroimage. 2006 Aug 15;32(2):592-602. doi: 10.1016/j.neuroimage.2006.04.201. Epub 2006 Jun 13.
Lateralization of memory by functional MRI (fMRI) may be helpful for surgical planning related to the medial temporal lobe (MTL). Most fMRI memory studies have calculated lateralization indices (LI) in the MTL from suprathreshold voxels only, but the selection of threshold remains highly arbitrary. We hypothesized that LIs could be reliably extracted from the distribution of voxels encompassing all positive T statistical values, each weighted by their own statistical significance. We also hypothesized that patient LIs that are two or more standard deviations (SD) away from the control group mean LI may be more clinically relevant than LIs that are not compared to control group. Thirteen healthy subjects had memory fMRI, and five epilepsy patients had both fMRI and the intracarotid amobarbital procedure (IAP). The fMRI task consisted of encoding patterns, scenes, and words. We found that normal subjects' LIs extracted from whole weighted statistical distributions tended to lateralize to the left for words, to the right for patterns, and intermediately for scenes, consistent with previous research. Weighted LIs were less variable than those calculated from suprathreshold voxels only. Using this approach, all patients had fMRI memory lateralizations consistent with IAP results. The weighted LIs provided a more clear-cut distinction of patients from the normal group (in terms of SDs from the group mean) than the suprathreshold voxel count approach. Our results suggest that using weighted distributions can be a useful strategy for assessing memory lateralization by fMRI in the MTL.
通过功能磁共振成像（fMRI）对记忆进行定侧，可能有助于与内侧颞叶（MTL）相关的手术规划。大多数fMRI记忆研究仅从超阈值体素计算MTL中的定侧指数（LI），但阈值的选择仍然非常随意。我们假设，可以从包含所有正T统计值的体素分布中可靠地提取LI，每个体素都根据其自身的统计显著性进行加权。我们还假设，与对照组平均LI相差两个或更多标准差（SD）的患者LI，可能比未与对照组比较的LI在临床上更具相关性。13名健康受试者进行了记忆fMRI检查，5名癫痫患者同时进行了fMRI检查和颈动脉内注射阿米妥试验（IAP）。fMRI任务包括对图案、场景和单词进行编码。我们发现，从整个加权统计分布中提取的正常受试者的LI，对于单词倾向于定侧到左侧，对于图案倾向于定侧到右侧，对于场景则介于两者之间，这与先前的研究一致。加权LI的变异性比仅从超阈值体素计算的LI更小。使用这种方法，所有患者的fMRI记忆定侧结果均与IAP结果一致。与超阈值体素计数方法相比，加权LI在区分患者与正常组方面（以与组均值的标准差衡量）更为明确。我们的结果表明，使用加权分布可能是通过fMRI评估MTL记忆定侧的一种有用策略。
