聋人与正常人枕叶视皮层对亮度敏感性的功能磁共振成像研究

目的　利用血氧水平依赖性功能磁共振成像 (BOLD fMRI)技术 ,探讨聋人在固定频率、不同亮度的点光源刺激下 ,枕叶视皮层的兴奋情况 ,并比较兴奋区的分布、范围、强度与正常人是否一致。方法　对 12例聋人和 15例正常人给予闪烁频率为 8Hz、亮度为 0 7、2 2、5 0 0、180 0lm的点光源刺激 ,同时应用GE 1 5TSignaHorizonLX超导型磁共振成像系统 ,采集其脑部的BOLD fMRI数据。通过AFNI软件进行统计分析得到脑功能活动的图像。结果　在 4种不同亮度的点光源刺激下 ,聋人与正常人的枕叶视皮层均有明显兴奋区 ,且主要兴奋区位于枕叶矩状裂周围的视皮层内 ;随着亮度的增加 ,聋人与正常人视皮层兴奋区内的活动像素数 (numberofactivatedpixels)显著增加 (F正常人 =4 2 7,P <0 0 5 ;F聋人 =6 41,P <0 0 5 ) ,且在较高亮度刺激下 ,聋人枕叶视皮层的兴奋性高于正常人 ,但两者差异无显著性意义 (F =2 17,P >0 0 5 ) ;聋人与正常人视皮层内所有兴奋像素的平均活动水平(activationlevel)随亮度的增加变化不大 ,而在 4种亮度刺激下均兴奋的像素的平均活动水平却随着亮度的增加而有较明显的增加 ,但无显著性差异 (F正常人 =0 79,P >0 0 5 ;F聋人 =1 6 ,P >0 0 5 )。结论聋人与正常人对亮度的基本反应特性是相

Effect of luminance contrast on BOLD-fMRI response in deaf and normal occipital visual cortex

Objective To examine the effect of luminance contrast stimulus by using blood oxygenation level dependent functional magnetic resonance imaging (BOLD fMRI) within deaf occipital visual cortex, and to compare the distribution, extent, and intensity of activated areas between deaf subjects and normal hearing subjects. Methods Twelve deaf subjects (average age 16.5) and 15 normal hearing subjects (average age 23.7) were stimulated by 4 kinds of luminance contrast (0.7, 2.2, 50.0, 180.0 lm). The fMRI data were collected on GE 1.5 T Signa Horizon LX MRI system and analyzed by AFNI to generate the activation map. Results Responding to all 4 kinds of stimulus luminance contrast, all deaf and normal subjects showed significant activations in occipital visual cortex. For both deaf and normal subjects, the number of activated pixels increased significantly with increasing luminance contrast( F normal =4.27, P <0.05; F deaf =6.41, P <0.05), and the susceptibility of deaf was somewhat higher than that of normal hearing subjects at the higher luminance contrast but there was no significant difference between them ( F =2.17, P >0.05). The local mean activation level for all activated pixels remained constant with increasing luminance contrast. However, there was an increase in the mean activation level for those activated pixels common to all trials as the stimulus luminance contrast was increased, but no significant difference was found within them ( F normal =0.79, P >0.05; F deaf =1.6, P >0.05). Conclusion The effect of luminance contrast on occipital visual cortex of deaf is similar to but somewhat higher than that of normal hearing subjects. In addition, it also proved that fMRI is a feasible method in the study of the deaf visual cortex.