静息状态默认脑活动网络的初步检验——听觉呈现语言任务

目的利用fMRI技术,通过听觉呈现语言任务,探讨刺激呈现通道对负激活脑区的影响,进一步检验静息状态人脑默认活动假说。方法13名健康成年志愿者参加实验。进行2次fMRI实验。实验1（简单任务）任务期要求受试者听无意义假词;实验2（复杂任务）要求受试者听真词并作词语属性判断（具体或抽象）。静息期要求受试者闭眼、静卧,不要做任何主动思维活动。利用SPM2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。并把本次实验结果与以往视觉呈现任务结果进行比较。结果初级视觉皮层与初级听觉皮层的负激活存在明显的通道依赖性,听觉呈现刺激引起视觉皮层负激活,视觉呈现刺激时听觉皮层表现为负激活。非任务依赖性负激活脑区包括扣带回后部/楔前叶（BA31/30）、扣带回前部（BA24/32）、两侧颞上回（BA8）、两颞下回前部（BA20）、两侧顶下小叶（BA39/40）。这些区域的负激活与刺激呈现通道方式及特定刺激任务无关。该负激活脑区模式与人类默认脑活动网络基本一致。结论刺激呈现通道是影响任务依赖性负激活的因素之一,探讨负激活问题时应该考虑到这一因素。同时,本研究进一步验证了静息状态时人脑默认活动假说。

A pilot exploration of resting state brain default mode network by using fMRI (Ⅱ): with auditory language tasks

Objective By using functional magnetic resonance imaging technique (fMRI), we examined whether stimuli modality (visually or acoustically) modulation of default mode network revealed by reverse subtracting deactivation. Methods Thirteen healthy volunteers participated in our fMRI expriments. Each subject performed two different language-related tasks that were acoustically presented. In Experiment 1 (simple task), subjects were instructed to hear simply the non-meaning Chinese words (pseudo-words). In Experiment 2 (complicated task), subjects were instructed to make silently the valence of the words (abstract or concrete) when heard them. Data were analyzed with SPM 2 soft- ware. We performed single subject and random effect group analysis, with employing reverse subtracting method to obtain the group averaged deactivation map. Results There are two major findings in our study. The deactivation in primary visual and auditory cortex appear to be modality dependence, with visually presented stimuli showing deactivation of primary auditory cortex and acoustically presented stimuli demonstrated primary visual cortex deactivation. Further more, the modality or task independent deactivation patterns were largely overlapped between the two experiments and compromised the so-called default mode brain networks. 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 8), bilateral inferior temporal gyrus (ITG, BA 20), and bilateral inferior parietal cortex (BA 39/40). Conclusion The stimuli presenting modality would be an important contribution to deactivation and we should consider this factor while exploring phenomenon of deactivation. In addition, our data further supported the notion that there exists default mode network activity during resting state.