Keshvari Fatemeh, Pouretemad Hamid-Reza, Ekhtiari Hamed
Department of Psychology, Shahid Beheshti University, G.C., Tehran, Iran.
Department of Psychology, Shahid Beheshti University, G.C., Tehran, Iran ; Instititute for Cognitive & Brain Sciences.
Basic Clin Neurosci. 2013 Summer;4(3):224-31.
Working memory plays a critical role in cognitive processes which are central to our daily life. Neuroimaging studies have shown that one of the most important areas corresponding to the working memory is the dorsolateral prefrontal cortex (DLFPC). This study was aimed to assess whether bilateral modulation of the DLPFC using a noninvasive brain stimulation, namely transcranial direct current stimulation (tDCS), modifies the working memory function in healthy adults.
In a randomized sham-controlled cross-over study, 60 subjects (30 Males) received sham and active tDCS in two subgroups (anode left/cathode right and anode right/cathode left) of the DLPFC. Subjects were presented working memory n-back task while the reaction time and accuracy were recorded.
A repeated measures, mixed design ANOVA indicated a significant difference between the type of stimulation (sham vs. active) in anodal stimulation of the left DLPFC with cathodal stimulation of the right DLPFC [F(1,55)= 5.29, P=0.019], but not the inverse polarity worsened accuracy in the 2-back working memory task. There were also no statistically significant changes in speed of working memory [F(1,55)= 0.458,P=0.502] related to type or order of stimulation.
The results would imply to a polarity dependence of bilateral tDCS of working memory. Left anodal/ right cathodal stimulation of DLPFC could impair working memory, while the reverser stimulation had no effect. Meaning that bilateral stimulation of DLFC would not be a useful procedure to improve working memory. Further studies are required to understand subtle effects of different tDCS stimulation/inhibition electrode positioning on the working memory.
工作记忆在认知过程中起着关键作用，而认知过程是我们日常生活的核心。神经影像学研究表明，与工作记忆相对应的最重要区域之一是背外侧前额叶皮层（DLFPC）。本研究旨在评估使用非侵入性脑刺激，即经颅直流电刺激（tDCS）对DLPFC进行双侧调制是否会改变健康成年人的工作记忆功能。
在一项随机假对照交叉研究中，60名受试者（30名男性）在DLPFC的两个亚组（阳极在左/阴极在右和阳极在右/阴极在左）中接受假刺激和主动tDCS。受试者在进行工作记忆n-back任务时，记录其反应时间和准确性。
重复测量混合设计方差分析表明，在左DLPFC阳极刺激与右DLPFC阴极刺激的情况下，刺激类型（假刺激与主动刺激）之间存在显著差异[F(1,55)= 5.29，P=0.019]，但相反极性在2-back工作记忆任务中并未使准确性变差。与刺激类型或顺序相关的工作记忆速度也没有统计学上的显著变化[F(1,55)= 0.458，P=0.502]。
结果表明工作记忆的双侧tDCS存在极性依赖性。DLPFC的左阳极/右阴极刺激可能会损害工作记忆，而反向刺激则没有效果。这意味着双侧刺激DLFC并不是改善工作记忆的有效方法。需要进一步研究以了解不同tDCS刺激/抑制电极定位对工作记忆的细微影响。
