McKendrick Ryan, Falcone Brian, Scheldrup Melissa, Ayaz Hasan
Northrop Grumman Company, Mission Systems, Falls Church, VA, United States.
Department of Psychology, George Mason University, Fairfax, VA, United States.
Front Hum Neurosci. 2020 Apr 9;14:64. doi: 10.3389/fnhum.2020.00064. eCollection 2020.
Transcranial direct current stimulation (tDCS) has been shown to be an inexpensive, safe, and effective way of augmenting a variety of cognitive abilities. Relatively recent advances in neuroimaging technology have provided the ability to measure brain activity concurrently during active brain stimulation rather than after stimulation. The effects on brain activity elicited by tDCS during active tDCS reported by initial studies have been somewhat conflicted and seemingly dependent on whether a behavioral improvement was observed. The current study set out to address questions regarding behavioral change, within and between-participant designs as well as differentiating the effects on hemodynamic amplitude and baseline during active tDCS stimulation. We tested the effects of transcranial direct current stimulation (tDCS) on anterior hemodynamics in prefrontal cortex during performance on a spatial memory task. Prefrontal cortex activity was measured with functional near infrared spectroscopy (fNIRS), a wearable and portable neuroimaging technique that utilizes near infrared light to measure cortical oxygenated and deoxygenated hemoglobin changes non-invasively. There were two groups, one group ( = 10) received only sham stimulation and the other group ( = 11) received sham followed by anodal stimulation to right ventral lateral prefrontal cortex. Analyses revealed an increase in spatial memory performance following tDCS stimulation. This augmented performance was accompanied by changes to oxygenation (HbO-HbR) at the onset of the hemodynamic response in bilateral dorsolateral prefrontal cortex and left ventral medial prefrontal cortex. In these regions we also observed that stimulation improved neural processing efficiency, by reducing oxygenation and increasing performance from block to block. During and following tDCS stimulation, it was also observed that in bilateral dorsolateral prefrontal cortex the relationship between performance and oxygenation inverted, from a negative relationship to a positive relationship. The results suggest that tDCS is predominately a mechanism for changing neurons propensity for activity as opposed to their strength of activity. tDCS not only alters the efficiency of task relevant processing, but also the nature in which hemodynamic resources are used during augmented task performance.
经颅直流电刺激（tDCS）已被证明是增强各种认知能力的一种廉价、安全且有效的方法。神经成像技术相对较新的进展使得在大脑主动刺激期间而非刺激后同时测量大脑活动成为可能。初步研究报道的主动tDCS期间tDCS引起的大脑活动效应有些相互矛盾，且似乎取决于是否观察到行为改善。本研究旨在解决关于行为变化、参与者内和参与者间设计的问题，以及区分主动tDCS刺激期间对血流动力学振幅和基线的影响。我们测试了经颅直流电刺激（tDCS）对空间记忆任务执行期间前额叶皮质前部血流动力学的影响。前额叶皮质活动通过功能性近红外光谱（fNIRS）进行测量，fNIRS是一种可穿戴的便携式神经成像技术，利用近红外光非侵入性地测量皮质氧合血红蛋白和脱氧血红蛋白的变化。共有两组，一组（n = 10）仅接受假刺激，另一组（n = 11）先接受假刺激，随后对右侧腹外侧前额叶皮质进行阳极刺激。分析显示，tDCS刺激后空间记忆表现有所提高。这种表现的增强伴随着双侧背外侧前额叶皮质和左侧腹内侧前额叶皮质血流动力学反应开始时氧合（HbO - HbR）的变化。在这些区域，我们还观察到刺激通过减少氧合并提高各块之间的表现来改善神经处理效率。在tDCS刺激期间及之后，还观察到在双侧背外侧前额叶皮质中，表现与氧合之间的关系发生了反转，从负相关变为正相关。结果表明，tDCS主要是一种改变神经元活动倾向而非活动强度的机制。tDCS不仅改变了任务相关处理的效率，还改变了增强任务表现期间血流动力学资源的使用方式。
