数字计算相关脑功能区偏侧化现象fMRI研究

目的 采用磁共振功能成像（fMRI）技术观察计算相关脑功能区的偏侧化现象，判断功能区偏侧化现象与利手因素及数字任务类型之间的关系，并对其原因进行初步分析。资料与方法 对7名左利手和25名右利手志愿者进行简单计算、复杂计算和数字位置判断实验。应用组块设计模式，采用GE 1．5T磁共振扫描仪，对所有志愿者行T1WI和fMRI。采用SPM99软件进行数据分析和脑功能区定位，记录各脑区激活像素数，计算偏侧化指数（LI），利用LI评价脑功能区的偏侧化现象。结果两组志愿者在执行三种任务时额叶功能区均以利手对侧激活占优势；顶下小叶偏侧化程度较低，但均以左侧激活略明显。在执行简单计算和复杂计算时，右利手组前额皮层、运动前区LI大于左利手组，额下回后部LI小于左利手组，顶下小叶偏侧化程度两组接近。两组中，与简单计算任务相比，执行复杂计算任务时前额皮层、运动前区和顶下小叶的LI均下降，而额下回后部LI增加。结论 fMRI可以检测数字计算相关的脑功能区的偏侧化现象，偏侧化现象与利手因素和任务类型有关。

The Laterality of Brain Functional Areas Related to Digital Calculations Revealed by Functional Magnetic Resonance Imaging

Objective To reveal the laterality of brain functional areas during performing digital calculations with fMRI, and to assess the relationship between laterality and handedness as well as type of arithmetical tasks, and postulate the possible reasons for laterality.Materials and Methods 25 right-handed and 7 left-handed healthy subjects received simple calculation, complex calculation, and proximity judgment experiment using block design. T_1WI and GRE-EPI fMRI were performed with a GE1.5T whole body MRI scanner. Statistics parameter mapping(SPM99) was used to process data and localize functional areas. Numbers of activated voxels were used to calculate laterality index (LI), which was used for the evaluation of the laterality of functional areas. Results For both groups, activation of functional areas in frontal lobe had a tendency in the nonpredominant hand side, but the functional areas in inferior parietal lobule had the left laterality. During simple and complex calculation, the laterality index of prefrontal cortex and premotor area was higher in right handed group than that in left handed group, but the laterality of inferior parietal lobule had no significant difference. In two groups, the difficulty of task increased the laterality of prefrontal cortex, premotor area, and inferior parietal lobule decreased, but the laterality of posterior part of inferior frontal gyrus increased.Conclusion The laterality of functional areas related to digital calculations can be detected with fMRI, the laterality of functional areas is related to handedness and task difficulty.