Chander Bankim S, Witkowski Matthias, Braun Christoph, Robinson Stephen E, Born Jan, Cohen Leonardo G, Birbaumer Niels, Soekadar Surjo R
Applied Neurotechnology Lab, Department of Psychiatry and Psychotherapy, University Hospital of Tübingen Tübingen, Germany.
MEG Center, University Hospital of TübingenTübingen, Germany; CIMeC, Center for Mind/Brain Sciences, University of TrentoTrento, Italy.
Front Cell Neurosci. 2016 May 6;10:120. doi: 10.3389/fncel.2016.00120. eCollection 2016.
Frontal midline theta (FMT) oscillations (4-8 Hz) are strongly related to cognitive and executive control during mental tasks such as memory processing, arithmetic problem solving or sustained attention. While maintenance of temporal order information during a working memory (WM) task was recently linked to FMT phase, a positive correlation between FMT power, WM demand and WM performance was shown. However, the relationship between these measures is not well understood, and it is unknown whether purposeful FMT phase manipulation during a WM task impacts FMT power and WM performance. Here we present evidence that FMT phase manipulation mediated by transcranial alternating current stimulation (tACS) can block WM demand-related FMT power increase (FMTΔpower) and disrupt normal WM performance.
Twenty healthy volunteers were assigned to one of two groups (group A, group B) and performed a 2-back task across a baseline block (block 1) and an intervention block (block 2) while 275-sensor magnetoencephalography (MEG) was recorded. After no stimulation was applied during block 1, participants in group A received tACS oscillating at their individual FMT frequency over the prefrontal cortex (PFC) while group B received sham stimulation during block 2. After assessing and mapping phase locking values (PLV) between the tACS signal and brain oscillatory activity across the whole brain, FMT power and WM performance were assessed and compared between blocks and groups.
During block 2 of group A but not B, FMT oscillations showed increased PLV across task-related cortical areas underneath the frontal tACS electrode. While WM task-related FMTΔpower and WM performance were comparable across groups in block 1, tACS resulted in lower FMTΔpower and WM performance compared to sham stimulation in block 2.
tACS-related manipulation of FMT phase can disrupt WM performance and influence WM task-related FMTΔpower. This finding may have important implications for the treatment of brain disorders such as depression and attention deficit disorder associated with abnormal regulation of FMT activity or disorders characterized by dysfunctional coupling of brain activity, e.g., epilepsy, Alzheimer's or Parkinson's disease (AD/PD).
额中线θ（FMT）振荡（4 - 8赫兹）在诸如记忆处理、算术问题解决或持续注意力等心理任务期间与认知和执行控制密切相关。虽然在工作记忆（WM）任务期间时间顺序信息的维持最近与FMT相位相关联，但FMT功率、WM需求和WM表现之间显示出正相关。然而，这些测量之间的关系尚未得到很好的理解，并且在WM任务期间有目的的FMT相位操纵是否会影响FMT功率和WM表现尚不清楚。在此，我们提供证据表明，经颅交流电刺激（tACS）介导的FMT相位操纵可阻断与WM需求相关的FMT功率增加（FMTΔ功率）并破坏正常的WM表现。
20名健康志愿者被分配到两组（A组、B组）中的一组，并在一个基线块（块1）和一个干预块（块2）中执行一个2 - 回溯任务，同时记录275个传感器的脑磁图（MEG）。在块1期间未施加刺激后，A组参与者在额叶前皮质（PFC）接受以其个体FMT频率振荡的tACS，而B组在块2期间接受假刺激。在评估并绘制整个大脑中tACS信号与脑振荡活动之间的锁相值（PLV）后，评估并比较块与组之间的FMT功率和WM表现。
在A组而非B组的块2期间，FMT振荡在额叶tACS电极下方与任务相关的皮质区域显示出增加的PLV。虽然在块1中两组之间与WM任务相关的FMTΔ功率和WM表现相当，但在块2中，与假刺激相比，tACS导致较低的FMTΔ功率和WM表现。
与tACS相关的FMT相位操纵可破坏WM表现并影响与WM任务相关的FMTΔ功率。这一发现可能对治疗诸如抑郁症和与FMT活动异常调节相关的注意力缺陷障碍等脑部疾病，或对以脑活动功能失调耦合为特征的疾病，如癫痫、阿尔茨海默病或帕金森病（AD/PD）具有重要意义。
