经颅直流电刺激干预工作记忆的脑功能网络研究

Study on the Brain Function Network of Transcranial Direct Current Stimulation Intervention on Working Memory

工作记忆是高级认知功能的重要基础,为探索经颅直流电刺激(t DCS)对工作记忆的影响及具体机制,招募18位被试参加实验,采集被试在伪/阳极/阴极t DCS刺激后三图、四图以及五图记忆负载任务中的行为数据(准确率、反应时长)与脑电信号。首先根据行为数据对工作记忆能力进行评估,再利用不同通道之间脑电信号的相关性,构建各状态下的脑功能网络,计算出平均度D、平均聚类系数C和全局效率E等网络特征参数,最后结合不同极性t DCS刺激后3种记忆负载任务中的行为数据与网络特征参数变化进行分析。研究表明,阳极刺激后四图与五图负载任务中的准确率(四图:89.75%±1.36%;五图:78.50%±2.25%)较伪刺激后(四图:81.25%±2.30%;五图:73.25%±5.36%)均有显著提升(P<0.05),而阴极刺激后行为数据的变化无规律可循。根据脑功能网络特征参数的变化可以发现,阳极刺激后高度值节点主要分布在刺激点F3以及周围区域,3种记忆负载任务中的网络特征参数与伪刺激后相比均显著增加(P<0.05),且在四图负载任务中增幅最大(伪刺激:D=10.55±2.31,C=0.60±0.07,E=0.26±0.03;阳极刺激:D=15.37±1.35,C=0.71±0.04,E=0.34±0.02),而阴极刺激后的高度值节点主要分布在右侧额叶与枕叶区域,且网络特征参数只在五图负载任务中表现出显著降低(伪刺激:D=13.73±2.42,C=0.64±0.07,E=0.31±0.04;阴极刺激:D=11.46±2.31,C=0.58±0.05,E=0.28±0.03)。结果表明,阳极刺激通过激活左背外侧前额叶皮层活性,可有效提升工作记忆性能,且在难度适中的任务中提升效果更显著;阴极刺激可抑制该皮层活性,使大脑连通性能下降,但大脑选择其他脑区进行功能代偿,有较大的个体差异性,且抑制效果在高难度任务下更显著。

Working memory is an important basis of advanced cognitive function.In order to explore the effect of transcranial direct current stimulation on working memory and its specific mechanism,18 subjects were recruited to participate in the experiment.The behavioral data(accuracy,reaction time)and EEG signals of subjects in the memory load task of three-picture,four-picture and five-picture after stimulation of sham/anode/cathode tDCS were collected.Firstly,the working memory ability was evaluated based on behavioral data.Then,the correlation of EEG signals between different channels was used to construct the brain functional network in each state,and the network characteristic parameters such as average degree(D),average clustering coefficient(C)and global efficiency(E)are calculated.Finally,the changes of behavior data and network characteristic parameters in three kind of memory load tasks after different tDCS stimulation are analyzed.It was shown that compared with sham tDCS(four-picture:81.25%±2.30%;five-picture:73.25%±5.36%),the accuracy of the four-picture and five-picture load tasks after anode tDCS(four-picture:89.75%±1.36%;five-picture:78.50%±2.25%)were significantly improved(P<0.05),but the behavior data after cathodic tDCS was irregular.According to the change of the characteristic parameters of brain functional network,the height value nodes after anode stimulation were mainly distributed in the stimulation point F3 and the surrounding area.The average degree,average clustering coefficient and global efficiency of the three kinds of memory load tasks were significantly increased compared with those after sham stimulation(P<0.05).The increase of the above three parameters in the four-picture task was the largest(sham tDCS:D=10.55±2.31,C=0.60±0.07,E=0.26±0.03;anodal tDCS:D=15.37±1.35,C=0.71±0.04,E=0.34±0.02).The height value nodes after cathode stimulation were mainly distributed in the right frontal lobe and occipital lobe.Only in the five-picture load task(sham tDCS:D=13.73±2.42,C=0.64±0.07,E=0.31±0.04;cathode tDCS:D=11.46±2.31,C=0.58±0.05,E=0.28±0.03),the average degree,average clustering coefficient and global efficiency are significantly reduced(P<0.05).The results showed that anode tDCS could effectively improve working memory performance by activating the activity of left dorsolateral prefrontal cortex,and the enhancement effect was more significant in the moderate difficulty task;cathode tDCS inhibited the activity of the cortex and reduce the connectivity of the brain,but the brain chose other brain regions for functional compensation,which showed great individual differences,and the inhibition effect was more significant in high difficulty tasks.