Polizzotto Nicola Riccardo, Ramakrishnan Nithya, Cho Raymond Y
Psychiatry and Behavioral Sciences, University of Texas Health Science Center at Houston, Houston, TX, United States.
Psychiatry and Behavioral Sciences, Baylor College of Medicine, Houston, TX, United States.
Front Psychol. 2020 May 26;11:939. doi: 10.3389/fpsyg.2020.00939. eCollection 2020.
A great deal of research has been performed with the promise of improving such critical cognitive functions as working memory (WM), with transcranial direct current stimulation (tDCS), a well-tolerated, inexpensive, easy-to-use intervention. Under the assumption that by delivering currents through electrodes placed in suitable locations on the scalp, it is possible to increase prefrontal cortex excitability and therefore improve WM. A growing number of studies have led to mixed results, leading to the realization that such oversimplified assumptions need revision. Models spanning currents to behavior have been advocated in order to reconcile and inform neurostimulation investigations. We articulate such multilevel exploration to tDCS/WM by briefly reviewing critical aspects at each level of analysis but focusing on the circuit level and how available biophysical WM models could inform tDCS. Indeed, such models should replace vague reference to cortical excitability changes with relevant tDCS net effects affecting neural computation and behavior in a more predictable manner. We will refer to emerging WM models and explore to what extent the general concept of excitation-inhibition (E/I) balance is a meaningful intermediate level of analysis, its relationship with gamma oscillatory activity, and the extent to which it can index tDCS effects. We will highlight some predictions that appear consistent with empirical evidence - such as non-linearities and trait dependency of effects and possibly a preferential effect on WM control functions - as well as limitations that appear related to the dynamical aspects of coding by persistent activity.
大量研究致力于通过经颅直流电刺激（tDCS）来改善诸如工作记忆（WM）等关键认知功能，tDCS是一种耐受性良好、价格低廉且易于使用的干预措施。其假设是，通过将电流通过放置在头皮合适位置的电极来传递，有可能提高前额叶皮质的兴奋性，从而改善工作记忆。然而，越来越多的研究得出了喜忧参半的结果，这使人们意识到这种过于简单的假设需要修正。为了协调并为神经刺激研究提供信息，人们提倡建立从电流到行为的模型。我们通过简要回顾每个分析层面的关键方面，但重点关注电路层面以及现有的生物物理工作记忆模型如何为tDCS提供信息，来阐述对tDCS/工作记忆的这种多层次探索。事实上，这样的模型应以更可预测的方式，用影响神经计算和行为的相关tDCS净效应，取代对皮质兴奋性变化的模糊提及。我们将提及新兴的工作记忆模型，并探讨兴奋-抑制（E/I）平衡这一总体概念在多大程度上是一个有意义的中间分析层面、它与伽马振荡活动的关系，以及它能在多大程度上表征tDCS效应。我们将强调一些与经验证据一致的预测——比如效应的非线性和特质依赖性，以及可能对工作记忆控制功能的优先效应——以及一些与持续活动编码的动态方面相关的局限性。
