Evidence of a large current of transcranial alternating current stimulation directly to deep brain regions

• Published in: Molecular psychiatry 2023-12, Vol.28 (12), p.5402-5410
• Main Authors: Shan, Yongzhi, Wang, Hongxing, Yang, Yanfeng, Wang, Jiahao, Zhao, Wenfeng, Huang, Yuda, Wang, Huang, Han, Bing, Pan, Na, Jin, Xiukun, Fan, Xiaotong, Liu, Yunyun, Wang, Jun, Wang, Changming, Zhang, Huaqiang, Chen, Sichang, Liu, Ting, Yan, Tianyi, Si, Tianmei, Yin, Lu, Li, Xinmin, Cosci, Fiammetta, Zhang, Xiangyang, Zhang, Guanghao, Gao, Keming, Zhao, Guoguang
• Format: Article
• Language: English
• Subjects: 631/1647; 631/378; 9/30; Adult; Amygdala; Amygdala - physiology; Amygdala - physiopathology; Behavioral Sciences; Biological Psychology; Brain; Brain - physiology; Brain - physiopathology; Cerebral Cortex - physiology; Cerebral Cortex - physiopathology; Deep Brain Stimulation - methods; Drug resistance; Drug Resistant Epilepsy - physiopathology; Drug Resistant Epilepsy - therapy; Electric currents; Electroencephalography - methods; Epilepsy; Female; Hippocampus; Hippocampus - physiology; Hippocampus - physiopathology; Humans; Insomnia; Insular Cortex - physiology; Male; Medicine; Medicine & Public Health; Mental disorders; Middle Aged; Neurosciences; Pharmacotherapy; Psychiatry; Sleep disorders; Transcranial Direct Current Stimulation - methods; Young Adult
• ISSN: 1359-4184; 1476-5578
• DOI: 10.1038/s41380-023-02150-8

Deep brain regions such as hippocampus, insula, and amygdala are involved in neuropsychiatric disorders, including chronic insomnia and depression. Our recent reports showed that transcranial alternating current stimulation (tACS) with a current of 15 mA and a frequency of 77.5 Hz, delivered through a montage of the forehead and both mastoids was safe and effective in intervening chronic insomnia and depression over 8 weeks. However, there is no physical evidence to support whether a large alternating current of 15 mA in tACS can send electrical currents to deep brain tissue in awake humans. Here, we directly recorded local field potentials (LFPs) in the hippocampus, insula and amygdala at different current strengths (1 to 15 mA) in 11 adult patients with drug-resistant epilepsy implanted with stereoelectroencephalography (SEEG) electrodes who received tACS at 77.5 Hz from 1 mA to 15 mA at 77.5 Hz for five minutes at each current for a total of 40 min. For the current of 15 mA at 77.5 Hz, additional 55 min were applied to add up a total of 60 min. Linear regression analysis revealed that the average LFPs for the remaining contacts on both sides of the hippocampus, insula, and amygdala of each patient were statistically associated with the given currents in each patient ( p