Siena Brain Investigation & Neuromodulation Lab (Si-BIN Lab), Department of Medicine, Surgery and Neuroscience, Neurology and Clinical Neurophysiology Section, University of Siena, Italy.
Non-invasive Brain Stimulation Unit, Department of Behavioral and Clinical Neurology, Santa Lucia Foundation IRCCS, Rome, Italy.
Neural Plast. 2022 Jul 16;2022:6197505. doi: 10.1155/2022/6197505. eCollection 2022.
Over the past few years, the possibility of modulating fast brain oscillatory activity in the gamma () band through transcranial alternating current stimulation (tACS) has been discussed in the context of both cognitive enhancement and therapeutic scenarios. However, the effects of tACS targeting regions outside the motor cortex, as well as its spatial specificity, are still unclear. Here, we present a concurrent tACS-fMRI block design study to characterize the impact of 40 Hz tACS applied over the left and right dorsolateral prefrontal cortex (DLPFC) in healthy subjects. Results suggest an increase in blood oxygenation level-dependent (BOLD) activity in the targeted bilateral DLPFCs, as well as in surrounding brain areas affected by stimulation according to biophysical modeling, i.e., the premotor cortex and anterior cingulate cortex (ACC). However, off-target effects were also observed, primarily involving the visual cortices, with further effects on the supplementary motor areas (SMA), left subgenual cingulate, and right superior temporal gyrus. The specificity of 40 Hz tACS over bilateral DLPFC and the possibility for network-level effects should be considered in future studies, especially in the context of recently promoted gamma-induction therapeutic protocols for neurodegenerative disorders.
在过去的几年中，通过经颅交流电刺激（tACS）调节伽马（γ）波段快速脑振荡活动的可能性在认知增强和治疗方案的背景下得到了讨论。然而，针对运动皮层以外区域的 tACS 的效果及其空间特异性仍不清楚。在这里，我们提出了一个同时进行的 tACS-fMRI 块设计研究，以描述在健康受试者中应用于左、右背外侧前额叶皮层（DLPFC）的 40Hz tACS 的影响。结果表明，靶向双侧 DLPFC 的血氧水平依赖（BOLD）活性增加，以及根据生物物理建模受刺激影响的周围脑区，即运动前皮质和前扣带皮质（ACC）。然而，也观察到了脱靶效应，主要涉及视觉皮质，对补充运动区（SMA）、左扣带回下区和右颞上回也有进一步的影响。在未来的研究中，特别是在最近提出的用于神经退行性疾病的伽马诱导治疗方案的背景下，应考虑 40Hz tACS 对双侧 DLPFC 的特异性和网络级效应的可能性。
