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Johnson L, Alekseichuk I, Krieg J, Doyle A, Yu Y, Vitek J, Johnson M, Opitz A. Dose-dependent effects of transcranial alternating current stimulation on spike timing in awake nonhuman primates. SCIENCE ADVANCES 2020; 6:eaaz2747. [PMID: 32917605 PMCID: PMC7467690 DOI: 10.1126/sciadv.aaz2747] [Citation(s) in RCA: 103] [Impact Index Per Article: 25.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Accepted: 07/16/2020] [Indexed: 05/07/2023]
Abstract
Weak extracellular electric fields can influence spike timing in neural networks. Approaches to noninvasively impose these fields on the brain have high therapeutic potential in neurology and psychiatry. Transcranial alternating current stimulation (TACS) is hypothesized to affect spike timing and cause neural entrainment. However, the conditions under which these effects occur in vivo are unknown. Here, we recorded single-unit activity in the neocortex in awake nonhuman primates during TACS and found dose-dependent neural entrainment to the stimulation waveform. Cluster analysis of changes in interspike intervals identified two main types of neural responses to TACS-increased burstiness and phase entrainment. Our results uncover key mechanisms of TACS and show that the stimulation affects spike timing in the awake primate brain at intensities feasible in humans. Thus, novel TACS protocols tailored to ongoing brain activity may be a tool to normalize spike timing in maladaptive brain networks and neurological disease.
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Affiliation(s)
- Luke Johnson
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jordan Krieg
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alex Doyle
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
| | - Ying Yu
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Jerrold Vitek
- Department of Neurology, University of Minnesota, Minneapolis, MN 55455, USA
| | - Matthew Johnson
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN 55455, USA.
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Alekseichuk I, Falchier AY, Linn G, Xu T, Milham MP, Schroeder CE, Opitz A. Electric field dynamics in the brain during multi-electrode transcranial electric stimulation. Nat Commun 2019; 10:2573. [PMID: 31189931 PMCID: PMC6561925 DOI: 10.1038/s41467-019-10581-7] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 05/20/2019] [Indexed: 11/29/2022] Open
Abstract
Neural oscillations play a crucial role in communication between remote brain areas. Transcranial electric stimulation with alternating currents (TACS) can manipulate these brain oscillations in a non-invasive manner. Recently, TACS using multiple electrodes with phase shifted stimulation currents were developed to alter long-range connectivity. Typically, an increase in coordination between two areas is assumed when they experience an in-phase stimulation and a disorganization through an anti-phase stimulation. However, the underlying biophysics of multi-electrode TACS has not been studied in detail. Here, we leverage direct invasive recordings from two non-human primates during multi-electrode TACS to characterize electric field magnitude and phase as a function of the phase of stimulation currents. Further, we report a novel "traveling wave" stimulation where the location of the electric field maximum changes over the stimulation cycle. Our results provide a mechanistic understanding of the biophysics of multi-electrode TACS and enable future developments of novel stimulation protocols.
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Affiliation(s)
- Ivan Alekseichuk
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA
| | - Arnaud Y Falchier
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
| | - Gary Linn
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
| | - Ting Xu
- Center for the Developing Brain, Child Mind Institute, New York, 10022, NY, USA
| | - Michael P Milham
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
- Center for the Developing Brain, Child Mind Institute, New York, 10022, NY, USA
| | - Charles E Schroeder
- Center for Biomedical Imaging and Neuromodulation, Nathan Kline Institute for Psychiatric Research, Orangeburg, 10962, NY, USA
- Departments of Neurological Surgery and Psychiatry, Columbia University College of Physicians and Surgeons, New York, 10032, NY, USA
| | - Alexander Opitz
- Department of Biomedical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA.
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