功能磁共振成像评价正常老年人视觉注意功能

目的研究正常老年人在完成视觉搜索任务时脑活动情况,旨在对相应的神经解剖基础进行初步探讨.方法13名正常老年人和12名正常年轻人参加了视觉搜索(单特征任务和联合特征任务,两者的差别是后者需要注意转换)的实验测试,同时采集其脑部的fMRI数据,通过功能神经成像分析软件SPM 99进行统计分析得到脑功能活动的图像.结果2个研究组在不同搜索任务下的脑区激活模式相似,均包括顶叶、额叶和枕叶、原始视皮层和皮层下等脑区,但不同脑区的激活强度和范围明显不同.在单特征任务下,正常老年组右侧顶上小叶(SPL)激活增加;同时两侧额叶激活增加,但以左额叶激活为主;原始视皮层激活减少.在联合特征搜索任务下,老年组双顶叶激活增加;左额叶激活增加,右额叶(BA6)额外出现激活,出现双额叶基本对称的激活模式;原始视皮层激活普遍减少.结论当任务所需求注意负荷增加时,老年组额叶信号的激活幅度明显增加,而且在需要最基本的注意调节时,额叶已有明显的代偿激活.

Assessment on the changes of visual attentionin healthy elderly by functional MRI

Objective To investigate functional activation patterns during two types of visual search tasks in old people with functional MRI, and probe neuro-anatomic basis of visual attention. Methods Thirteen healthy subjects and 12 young people participated in the experiment designed with two visual search tasks. The first was a "pop-out" single feature task, detecting a vertical target among horizontal distractors. The second was a conjunction task, where the target is defined by a conjunction of feature (color and orientation) and where performance depends on some shifting of attention. The fMRI data were collected on SIEMENS Sonata 1.5T systems and analyzed by SPM 99 software to generate the activation map. Results Although both groups revealed overlapping networks engaged in the both tasks including the parietal lobule, frontal and occipital cortical regions, primary visual cortex and some subcortical structures, there were remarkable differences in the extent of activation of these brain regions between groups. In the pop-out condition the more activations were demonstrated in the right superior parietal lobule and bilateral frontal regions (mainly in the left), while less activation was found in the primary visual cortex for the old people. The more activations were demonstrated in bilateral parietal lobule and left frontal regions, extra activation was in the right lobes, presenting basically symmetrical activation in the bilateral frontal lobes. primary visual cortex also had less activations in the conjunction condition. Conclusion Old people have more extent of activations in the frontal lobes in the visual search task requiring more attentional resource, even in the course of the basic attention modulation, there are compensatory activations in the frontal lobes.