静息状态默认脑活动网络的初步检验——视觉呈现语言任务

目的：利用fMRI技术初步检验静息状态人脑默认活动假说及其脑区网络组成与刺激呈现通道的关系。方法：13名健康成年志愿者参加实验。每位受试者进行2次fMRI实验，任务通过视觉呈现。实验1（简单任务）任务期要求受试者注视无意义假词并默述；实验2（复杂任务）要求受试者完成动词产生任务。注视显示器上交替出现的“＋”及“＋＋＋”作为控制任务。利用SPM99软件进行数据处理。先分析单个被试，然后行组间比较。采用反减法获得负激活图，对有关脑区的反应特性做进一步分析。结果：实验1和实验2负激活脑区大部分相同，主要包括扣带回后部／楔前叶（BA31／30）、扣带回前部（BA24／32）、右侧颞上回（BA8）、左侧颞上回（BA8）、右颞下回前部（BA20）、左颞下回前部（BA20）、右侧顶下小叶（BA39／40）、左侧顶下小叶（BA39／40）。这些脑区的BOLD反应曲线呈负性变化，扣带回后部的负激活强度复杂任务时强于简单任务。结论：本研究初步验证了静息状态人脑默认活动假说及其负激活程度与任务难度的相关性。

A pilot exploration of resting state brain default mode network hypothesis by using fMRI: with visually presented language tasks

Objective By using functional magnetic resonance imaging (fMRI), we preliminarily test the resting state brain default mode network hypothesis and characterize the brain regions consisting of this network. Methods Thirteen healthy volunteers participated in our fMRI experiments. Each subject performed two different language-related task that was visually presented. In experiment 1 (simple task), subjects were instructed to simply fix the non-meaning Chinese words (pseudo-words) and made silent read for them. In experiment 2 (complicated task), subjects were instructed to produce a verb corresponding to the noun that presented on the screen. During control condition, subjects simply fixed on the cross. Data were analyzed with SPM99 software. We performed single subject and group averaging analysis individually. We used reverse subtracting method to obtain the group averaged deactivation map and further explored the characteristic of BOLD single changes in some of the deactivated brain regions. Results Our data revealed nearly overlapping deactivated brain pattern between the two experiments. These brain regions included posterior cingulate and precuneous cortex (PCC, BA 31/30), anterior cingulate cortex (ACC, BA 24/32), bilateral superior temporal gyrus (STG, BA), bilateral inferior temporal gyrus (ITG, BA 20), and bilateral inferior parietal cortex (BA 39/40). All of these regions had a negative BOLD response during the task and the deactivation magnitude of PCC was significant great in experiment 2 than in experiment 1. Conclusion This study supported the notion that there exist default mode network activity during resting state and demonstrated its activity level might be modulated with cognition demanding of external task.