1
|
Lee S, Park J, Lee C, Ahn J, Ryu J, Lee SH, Im CH. Determination of optimal injection current pattern for multichannel transcranial electrical stimulation without individual MRI using multiple head models. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2024; 243:107878. [PMID: 37890288 DOI: 10.1016/j.cmpb.2023.107878] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/20/2023] [Revised: 10/09/2023] [Accepted: 10/19/2023] [Indexed: 10/29/2023]
Abstract
BACKGROUND AND OBJECTIVE Multichannel transcranial electrical stimulation (tES) is widely used to achieve improved stimulation focality. In the multichannel tES, the injection current pattern is generally determined through an optimization process with a finite element (FE) head model extracted from individual magnetic resonance images (MRIs). Although using an individual head model ensures the best outcome, acquiring MRIs of individual subjects in many practical applications is often difficult. Alternatively, a standard head model can be used to determine the optimal injection current pattern to stimulate a specific target; however, this may result in a relatively inaccurate delivery of stimulation current owing to the difference in individual anatomical structures. To address this issue, we propose a new approach for determining the injection current pattern using multiple head models, which can improve the stimulation focality compared to that achieved with a single standard head model. METHODS Twenty FE head models were used to optimize the injection current patterns to stimulate three cortical regions that are widely considered targets for tES. The individual injection current patterns were then averaged to obtain each target's mean injection current pattern. The stimulation focality for each target was then calculated by applying different current patterns (the mean current, individual current, and current from a standard model). RESULTS Our results showed that the stimulation focality obtained using the mean injection current pattern was significantly higher than that obtained using the injection current pattern from a standard head model. Additionally, our results demonstrated that a minimum of 13 head models are required to determine mean current pattern, allowing for a higher stimulation focality than when using the current from a standard head model. CONCLUSIONS Hence, using multiple head models can provide a viable solution for improving the stimulation efficacy of multichannel tES when individual MRIs are not available.
Collapse
Affiliation(s)
- Sangjun Lee
- Department of Electronic Engineering, Hanyang University, Seoul, Republic of Korea; Department of Biomedical Engineering, Hanyang University, Seoul, Republic of Korea
| | - Jimin Park
- Department of Electronic Engineering, Hanyang University, Seoul, Republic of Korea
| | - Chany Lee
- Cognitive Science Research Group, Korea Brain Research Institute, Daegu, Republic of Korea
| | - Jeongyeol Ahn
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Republic of Korea
| | - Juhyoung Ryu
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Republic of Korea
| | - Sang-Hun Lee
- Department of Brain and Cognitive Sciences, Seoul National University, Seoul, Republic of Korea
| | - Chang-Hwan Im
- Department of Electronic Engineering, Hanyang University, Seoul, Republic of Korea; Department of Biomedical Engineering, Hanyang University, Seoul, Republic of Korea.
| |
Collapse
|
2
|
Veiga AL, Fernandez-Corazza M, van Raap MBF, Spinelli EM. Imaging of Magnetic Nanoparticles With Permeability Tomography. IEEE Trans Biomed Eng 2023; 70:3216-3226. [PMID: 37285258 DOI: 10.1109/tbme.2023.3283787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Magnetic nanoparticles are being increasingly used in numerous biomedical applications for diagnosis and therapy. During the course of these applications nanoparticle biodegradation and body clearance may occur. In this context, a portable, non-invasive, non-destructive and contactless imaging device can be relevant to trace the nanoparticle distribution before and after the medical procedure. We present a method for in vivo imaging the nanoparticles based on the magnetic induction technique, and we show how to properly tune it for magnetic permeability tomography, maximizing the permeability selectivity. A tomograph prototype was designed and built to demonstrate the feasibility of the proposed method. It includes data collection, signal processing and image reconstruction. Useful selectivity and resolution are achieved on phantoms and animals, proving that the device can be used to monitor the presence of magnetic nanoparticles without requiring any particular sample preparation. By this way, we show that magnetic permeability tomography may become a powerful technique to assist medical procedures.
Collapse
|
3
|
Wang M, Lou K, Liu Z, Wei P, Liu Q. Multi-objective optimization via evolutionary algorithm (MOVEA) for high-definition transcranial electrical stimulation of the human brain. Neuroimage 2023; 280:120331. [PMID: 37604295 DOI: 10.1016/j.neuroimage.2023.120331] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2023] [Revised: 07/01/2023] [Accepted: 08/14/2023] [Indexed: 08/23/2023] Open
Abstract
Designing a transcranial electrical stimulation (tES) strategy requires considering multiple objectives, such as intensity in the target area, focality, stimulation depth, and avoidance zone. These objectives are often mutually exclusive. In this paper, we propose a general framework, called multi-objective optimization via evolutionary algorithm (MOVEA), which solves the non-convex optimization problem in designing tES strategies without a predefined direction. MOVEA enables simultaneous optimization of multiple targets through Pareto optimization, generating a Pareto front after a single run without manual weight adjustment and allowing easy expansion to more targets. This Pareto front consists of optimal solutions that meet various requirements while respecting trade-off relationships between conflicting objectives such as intensity and focality. MOVEA is versatile and suitable for both transcranial alternating current stimulation (tACS) and transcranial temporal interference stimulation (tTIS) based on high definition (HD) and two-pair systems. We comprehensively compared tACS and tTIS in terms of intensity, focality, and steerability for targets at different depths. Our findings reveal that tTIS enhances focality by reducing activated volume outside the target by 60%. HD-tTIS and HD-tDCS can achieve equivalent maximum intensities, surpassing those of two-pair tTIS, such as 0.51 V/m under HD-tACS/HD-tTIS and 0.42 V/m under two-pair tTIS for the motor area as a target. Analysis of variance in eight subjects highlights individual differences in both optimal stimulation policies and outcomes for tACS and tTIS, emphasizing the need for personalized stimulation protocols. These findings provide guidance for designing appropriate stimulation strategies for tACS and tTIS. MOVEA facilitates the optimization of tES based on specific objectives and constraints, advancing tTIS and tACS-based neuromodulation in understanding the causal relationship between brain regions and cognitive functions and treating diseases. The code for MOVEA is available at https://github.com/ncclabsustech/MOVEA.
Collapse
Affiliation(s)
- Mo Wang
- Department of Biomedical Engineering, Southern University of Science and Technology, China.
| | - Kexin Lou
- Department of Biomedical Engineering, Southern University of Science and Technology, China; School of Electrical Engineering and Computer Science, University of Queensland, Australia.
| | - Zeming Liu
- Department of Biomedical Engineering, Southern University of Science and Technology, China.
| | - Pengfei Wei
- Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, China.
| | - Quanying Liu
- Department of Biomedical Engineering, Southern University of Science and Technology, China.
| |
Collapse
|
4
|
Havlík M, Hlinka J, Klírová M, Adámek P, Horáček J. Towards causal mechanisms of consciousness through focused transcranial brain stimulation. Neurosci Conscious 2023; 2023:niad008. [PMID: 37089451 PMCID: PMC10120840 DOI: 10.1093/nc/niad008] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 01/10/2023] [Accepted: 03/30/2023] [Indexed: 04/25/2023] Open
Abstract
Conscious experience represents one of the most elusive problems of empirical science, namely neuroscience. The main objective of empirical studies of consciousness has been to describe the minimal sets of neural events necessary for a specific neuronal state to become consciously experienced. The current state of the art still does not meet this objective but rather consists of highly speculative theories based on correlates of consciousness and an ever-growing list of knowledge gaps. The current state of the art is defined by the limitations of past stimulation techniques and the emphasis on the observational approach. However, looking at the current stimulation technologies that are becoming more accurate, it is time to consider an alternative approach to studying consciousness, which builds on the methodology of causal explanations via causal alterations. The aim of this methodology is to move beyond the correlates of consciousness and focus directly on the mechanisms of consciousness with the help of the currently focused brain stimulation techniques, such as geodesic transcranial electric neuromodulation. This approach not only overcomes the limitations of the correlational methodology but will also become another firm step in the following science of consciousness.
Collapse
Affiliation(s)
- Marek Havlík
- Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic
| | - Jaroslav Hlinka
- Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic
- Department of Complex Systems, Institute of Computer Science of the Czech Academy of Sciences, Pod Vodárenskou věží 271/2, Prague 182 07, Czech Republic
| | - Monika Klírová
- Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic
- Third Faculty of Medicine, Charles University, Ruská 87, Prague 10 100 00, Czech Republic
| | - Petr Adámek
- Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic
- Third Faculty of Medicine, Charles University, Ruská 87, Prague 10 100 00, Czech Republic
| | - Jiří Horáček
- Center for Advanced Studies of Brain and Consciousness, National Institute of Mental Health, Topolová 748, Klecany 250 67, Czech Republic
- Third Faculty of Medicine, Charles University, Ruská 87, Prague 10 100 00, Czech Republic
| |
Collapse
|
5
|
Ahsan F, Chi T, Cho R, Sheth SA, Goodman W, Aazhang B. EMvelop stimulation: minimally invasive deep brain stimulation using temporally interfering electromagnetic waves. J Neural Eng 2022; 19. [PMID: 35700717 DOI: 10.1088/1741-2552/ac7894] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2022] [Accepted: 06/14/2022] [Indexed: 11/12/2022]
Abstract
OBJECTIVE Recently, the temporal interference stimulation (TIS) technique for focal noninvasive deep brain stimulation (DBS) was reported. However, subsequent computational modeling studies on the human brain have shown that while TIS achieves higher focality of electric fields than state-of-the-art methods, further work is needed to improve the stimulation strength. Here, we investigate the idea of EMvelop stimulation, a minimally invasive DBS setup using temporally interfering gigahertz (GHz) electromagnetic (EM) waves. At GHz frequencies, we can create antenna arrays at the scale of a few centimeters or less that can be endocranially implanted to enable longitudinal stimulation and circumvent signal attenuation due to the scalp and skull. Furthermore, owing to the small wavelength of GHz EM waves, we can optimize both amplitudes and phases of the EM waves to achieve high intensity and focal stimulation at targeted regions within the safety limit for exposure to EM waves. APPROACH We develop a simulation framework investigating the propagation of GHz EM waves generated by line current antenna elements and the corresponding heat generated in the brain tissue. We propose two optimization flows to identify antenna current amplitudes and phases for either maximal intensity or maximal focality transmission of the interfering electric fields with EM waves safety constraint. MAIN RESULTS A representative result of our study is that with two endocranially implanted arrays of size 4.2 cm × 4.7 cm each, we can achieve an intensity of 12 V/m with a focality of 3.6 cm at a target deep in the brain tissue. SIGNIFICANCE In this proof-of-principle study, we show that the idea of EMvelop stimulation merits further investigation as it can be a minimally invasive way of stimulating deep brain targets and offers benefits not shared by prior methodologies of electrical or magnetic stimulation.
Collapse
Affiliation(s)
- Fatima Ahsan
- Electrical and computer engineering, Rice University, 6100 Main Street, Houston, Texas, 77005, UNITED STATES
| | - Taiyun Chi
- Department of Electrical and Computer Engineering and Neuroengineering Initiative, Rice University, 6100 Main Street, Houston, Texas, 77005-1892, UNITED STATES
| | - Raymond Cho
- Menninger Department of Psychiatry and Behavioral Sciences, Baylor College of Medicine, 1 Baylor Plaza, Houston, TX 77030, Houston, Texas, 77030-3411, UNITED STATES
| | - Sameer A Sheth
- Neurosurgery, Baylor College of Medicine, Baylor College of Medicine, Neurosurgery Houston, TX, USA, Houston, Texas, 77030, UNITED STATES
| | - Wayne Goodman
- Psychiatry, Baylor College of Medicine, Baylor College of Medicine, Psychiatry Houston, TX, USA, Houston, Texas, 77030, UNITED STATES
| | - Behnaam Aazhang
- Department of Electrical and Computer Engineering, Rice University, George R. Brown School of Engineering, 6100 Main Street, Houston, TX 77005, USA, Houston, 77005, UNITED STATES
| |
Collapse
|
6
|
Olgiati E, Malhotra PA. Using non-invasive transcranial direct current stimulation for neglect and associated attentional deficits following stroke. Neuropsychol Rehabil 2022; 32:732-763. [PMID: 32892712 DOI: 10.1080/09602011.2020.1805335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Neglect is a disabling neuropsychological syndrome that is frequently observed following right-hemispheric stroke. Affected individuals often present with multiple attentional deficits, ranging from reduced orienting towards contralesional space to a generalized impairment in maintaining attention over time. Although a degree of spontaneous recovery occurs in most patients, in some individuals this condition can be treatment-resistant with prominent ongoing non-spatial deficits. Further, there is a large inter-individual variability in response to different therapeutic approaches. Given its potential to alter neuronal excitability and affect neuroplasticity, non-invasive brain stimulation is a promising tool that could potentially be utilized to facilitate recovery. However, there are many outstanding questions regarding its implementation in this heterogeneous patient group. Here we provide a critical overview of the available evidence on the use of non-invasive electrical brain stimulation, focussing on transcranial direct current stimulation (tDCS), to improve neglect and associated attentional deficits after right-hemispheric stroke. At present, there is insufficient robust evidence supporting the clinical use of tDCS to alleviate symptoms of neglect. Future research would benefit from careful study design, enhanced precision of electrical montages, multi-modal approaches exploring predictors of response, tailored dose-control applications and increased efforts to evaluate standalone tDCS versus its incorporation into combination therapy.
Collapse
Affiliation(s)
- Elena Olgiati
- Department of Brain Sciences, Imperial College London, London, UK.,Imperial College Healthcare NHS Trust, London, UK
| | - Paresh A Malhotra
- Department of Brain Sciences, Imperial College London, London, UK.,Imperial College Healthcare NHS Trust, London, UK.,UK Dementia Research Institute, Care Research & Technology Centre, Imperial College London and University of Surrey, London, UK
| |
Collapse
|
7
|
Abstract
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique to treat brain disorders by using a constant, low current to stimulate targeted cortex regions. Compared to the conventional tDCS that uses two large pad electrodes, multiple electrode tDCS has recently received more attention. It is able to achieve better stimulation performance in terms of stimulation intensity and focality. In this paper, we first establish a computational model of tDCS, and then propose a novel optimization algorithm using a regularization matrix λ to explore the balance between stimulation intensity and focality. The simulation study is designed such that the performance of state-of-the-art algorithms and the proposed algorithm can be compared via quantitative evaluation. The results show that the proposed algorithm not only achieves desired intensity, but also smaller target error and better focality. Robustness analysis indicates that the results are stable within the ranges of scalp and cerebrospinal fluid (CSF) conductivities, while the skull conductivity is most sensitive and should be carefully considered in real clinical applications.
Collapse
|
8
|
Beumer S, Boon P, Klooster DCW, van Ee R, Carrette E, Paulides MM, Mestrom RMC. Personalized tDCS for Focal Epilepsy—A Narrative Review: A Data-Driven Workflow Based on Imaging and EEG Data. Brain Sci 2022; 12:brainsci12050610. [PMID: 35624997 PMCID: PMC9139054 DOI: 10.3390/brainsci12050610] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Revised: 05/03/2022] [Accepted: 05/05/2022] [Indexed: 02/01/2023] Open
Abstract
Conventional transcranial electric stimulation(tES) using standard anatomical positions for the electrodes and standard stimulation currents is frequently not sufficiently selective in targeting and reaching specific brain locations, leading to suboptimal application of electric fields. Recent advancements in in vivo electric field characterization may enable clinical researchers to derive better relationships between the electric field strength and the clinical results. Subject-specific electric field simulations could lead to improved electrode placement and more efficient treatments. Through this narrative review, we present a processing workflow to personalize tES for focal epilepsy, for which there is a clear cortical target to stimulate. The workflow utilizes clinical imaging and electroencephalography data and enables us to relate the simulated fields to clinical outcomes. We review and analyze the relevant literature for the processing steps in the workflow, which are the following: tissue segmentation, source localization, and stimulation optimization. In addition, we identify shortcomings and ongoing trends with regard to, for example, segmentation quality and tissue conductivity measurements. The presented processing steps result in personalized tES based on metrics like focality and field strength, which allow for correlation with clinical outcomes.
Collapse
Affiliation(s)
- Steven Beumer
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
- Correspondence:
| | - Paul Boon
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
- Department of Neurology, Ghent University Hospital, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Debby C. W. Klooster
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
- Department of Neurology, Ghent University Hospital, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Raymond van Ee
- Philips Research Eindhoven, High Tech Campus 34, 5656 AE Eindhoven, The Netherlands;
| | - Evelien Carrette
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
- Department of Neurology, Ghent University Hospital, Corneel Heymanslaan 10, 9000 Ghent, Belgium
| | - Maarten M. Paulides
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
- Department of Radiation Oncology, Erasmus Medical Center Cancer Institute, Burgemeester Oudlaan 50, 3062 PA Rotterdam, The Netherlands
| | - Rob M. C. Mestrom
- Department of Electrical Engineering, University of Technology Eindhoven, P.O. Box 513, 5600 MB Eindhoven, The Netherlands; (P.B.); (D.C.W.K.); (E.C.); (M.M.P.); (R.M.C.M.)
| |
Collapse
|
9
|
Gomez-Feria J, Fernandez-Corazza M, Martin-Rodriguez JF, Mir P. TMS intensity and focality correlation with coil orientation at three non-motor regions. Phys Med Biol 2022; 67. [DOI: 10.1088/1361-6560/ac4ef9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Accepted: 01/26/2022] [Indexed: 11/11/2022]
Abstract
Abstract
Objective. The aim of this study is to define the best coil orientations for transcranial magnetic stimulation (TMS) for three clinically relevant brain areas: pre-supplementary motor area (pre-SMA), inferior frontal gyrus (IFG), and posterior parietal cortex (PPC), by means of simulations in 12 realistic head models of the electric field (E-field). Methods. We computed the E-field generated by TMS in our three volumes of interest (VOI) that were delineated based on published atlases. We then analysed the maximum intensity and spatial focality for the normal and absolute components of the E-field considering different percentile thresholds. Lastly, we correlated these results with the different anatomical properties of our VOIs. Results. Overall, the spatial focality of the E-field for the three VOIs varied depending on the orientation of the coil. Further analysis showed that differences in individual brain anatomy were related to the amount of focality achieved. In general, a larger percentage of sulcus resulted in better spatial focality. Additionally, a higher normal E-field intensity was achieved when the coil axis was placed perpendicular to the predominant orientations of the gyri of each VOI. A positive correlation between spatial focality and E-field intensity was found for PPC and IFG but not for pre-SMA. Conclusions. For a rough approximation, better coil orientations can be based on the individual’s specific brain morphology at the VOI. Moreover, TMS computational models should be employed to obtain better coil orientations in non-motor regions of interest. Significance. Finding better coil orientations in non-motor regions is a challenge in TMS and seeks to reduce interindividual variability. Our individualized TMS simulation pipeline leads to fewer inter-individual variability in the focality, likely enhancing the efficacy of the stimulation and reducing the risk of stimulating adjacent, non-targeted areas.
Collapse
|
10
|
Louviot S, Tyvaert L, Maillard LG, Colnat-Coulbois S, Dmochowski J, Koessler L. Transcranial Electrical Stimulation generates electric fields in deep human brain structures. Brain Stimul 2021; 15:1-12. [PMID: 34742994 DOI: 10.1016/j.brs.2021.11.001] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2021] [Revised: 10/21/2021] [Accepted: 11/01/2021] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Transcranial electrical stimulation (TES) efficiency is related to the electric field (EF) magnitude delivered on the target. Very few studies (n = 4) have estimated the in-vivo intracerebral electric fields in humans. They have relied mainly on electrocorticographic recordings, which require a craniotomy impacting EF distribution, and did not investigate deep brain structures. OBJECTIVE To measure the electric field in deep brain structures during TES in humans in-vivo. Additionally, to investigate the effects of TES frequencies, intensities, and montages on the intracerebral EF. METHODS Simultaneous bipolar transcranial alternating current stimulation and intracerebral recordings (SEEG) were performed in 8 drug-resistant epileptic patients. TES was applied using small high-definition (HD) electrodes. Seven frequencies, two intensities and 15 montages were applied on one, six and one patients, respectively. RESULTS At 1 mA intensity, we found mean EF magnitudes of 0.21, 0.17 and 0.07 V·m-1 in the amygdala, hippocampus, and cingulate gyrus, respectively. An average of 0.14 ± 0.07 V·m-1 was measured in these deep brain structures. Mean EF magnitudes in these structures at 1Hz were 11% higher than at 300Hz (+0.03 V·m-1). The EF was correlated with the TES intensities. The TES montages that yielded the maximum EF in the amygdalae were T7-T8 and in the cingulate gyri were C3-FT10 and T7-C4. CONCLUSION TES at low intensities and with small HD electrodes can generate an EF in deep brain structures, irrespective of stimulation frequency. EF magnitude is correlated to the stimulation intensity and depends upon the stimulation montage.
Collapse
Affiliation(s)
- Samuel Louviot
- Université de Lorraine, CNRS, CRAN, F-54000, Nancy, France
| | - Louise Tyvaert
- Université de Lorraine, CNRS, CRAN, F-54000, Nancy, France; Université de Lorraine, CHRU-Nancy, Service de Neurologie, F-54000, Nancy, France
| | - Louis G Maillard
- Université de Lorraine, CNRS, CRAN, F-54000, Nancy, France; Université de Lorraine, CHRU-Nancy, Service de Neurologie, F-54000, Nancy, France
| | - Sophie Colnat-Coulbois
- Université de Lorraine, CNRS, CRAN, F-54000, Nancy, France; Université de Lorraine, CHRU-Nancy, Service de Neurochirurgie, F-54000, Nancy, France
| | - Jacek Dmochowski
- Department of Biomedical Engineering, City College of New York, New York, NY, USA
| | | |
Collapse
|
11
|
Jog M, Anderson C, Kim E, Garrett A, Kubicki A, Gonzalez S, Jann K, Iacoboni M, Woods R, Wang DJ, Narr KL. A novel technique for accurate electrode placement over cortical targets for transcranial electrical stimulation (tES) clinical trials. J Neural Eng 2021; 18. [PMID: 34555822 DOI: 10.1088/1741-2552/ac297d] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2021] [Accepted: 09/23/2021] [Indexed: 11/12/2022]
Abstract
Objective. We present an easy-to-implement technique for accurate electrode placement over repeated transcranial electrical stimulation (tES) sessions across participants and time. tES is an emerging, non-invasive neuromodulation technique that delivers electrical stimulation using scalp electrodes.Approach.The tES electrode placement technique was developed during an exploratory clinical trial aimed at targeting a specific MNI-atlas cortical coordinate inN= 59 depressed participants (32 F, mean age: 31.1 ± 8.3 SD). Each participant completed 12 sessions of active or sham stimulation, administered using high-definition (HD) or conventional sized electrode montages placed according to the proposed technique. Neuronavigation data measuring the distances between the identified and the intended stimulation site, simulations, and cerebral blood flow (CBF) data at baseline and post-treatment were acquired to evaluate the targeting characteristics of the proposed technique.Main results.Neuronavigation measurements indicate accurate electrode placement to within 1 cm of the stimulation target on average across repeated sessions. Simulations predict that these placement characteristics result in minimal electric field differences at the stimulation target (>0.90 correlation, and <10% change in the modal electric field and targeted volume). Additionally, significant changes in %CBF (relative to baseline) under the stimulation target in the active stimulation group relative to sham confirmed that the proposed placement technique introduces minimal bias in the spatial location of the cortical coordinate ultimately targeted. Finally, we show proof of concept that the proposed technique provides similar accuracy of electrode placement at other cortical targets.Significance.For voxel-level cortical targets, existing techniques based on cranial landmarks are suboptimal. Our results show that the proposed electrode placement approach provides high consistency for the accurate targeting of such specific cortical regions. Overall, the proposed technique now enables the accurate targeting of locations not accessible with the existing 10-20 system such as scalp-projections of clinically-relevant cortical coordinates identified by brain mapping studies. Clinical trial ID: NCT03556124.
Collapse
Affiliation(s)
- Mayank Jog
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Cole Anderson
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Elizabeth Kim
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Avery Garrett
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Antoni Kubicki
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Sara Gonzalez
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Kay Jann
- Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Marco Iacoboni
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Roger Woods
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| | - Danny Jj Wang
- Stevens Neuroimaging and Informatics Institute, University of Southern California, Los Angeles, CA, United States of America
| | - Katherine L Narr
- Department of Neurology, University of California Los Angeles, Los Angeles, CA, United States of America
| |
Collapse
|
12
|
Klírová M, Voráčková V, Horáček J, Mohr P, Jonáš J, Dudysová DU, Kostýlková L, Fayette D, Krejčová L, Baumann S, Laskov O, Novák T. Modulating Inhibitory Control Processes Using Individualized High Definition Theta Transcranial Alternating Current Stimulation (HD θ-tACS) of the Anterior Cingulate and Medial Prefrontal Cortex. Front Syst Neurosci 2021; 15:611507. [PMID: 33859554 PMCID: PMC8042221 DOI: 10.3389/fnsys.2021.611507] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 03/04/2021] [Indexed: 02/02/2023] Open
Abstract
Increased frontal midline theta activity generated by the anterior cingulate cortex (ACC) is induced by conflict processing in the medial frontal cortex (MFC). There is evidence that theta band transcranial alternating current stimulation (θ-tACS) modulates ACC function and alters inhibitory control performance during neuromodulation. Multi-electric (256 electrodes) high definition θ-tACS (HD θ-tACS) using computational modeling based on individual MRI allows precise neuromodulation targeting of the ACC via the medial prefrontal cortex (mPFC), and optimizes the required current density with a minimum impact on the rest of the brain. We therefore tested whether the individualized electrode montage of HD θ-tACS with the current flow targeted to the mPFC-ACC compared with a fixed montage (non-individualized) induces a higher post-modulatory effect on inhibitory control. Twenty healthy subjects were randomly assigned to a sequence of three HD θ-tACS conditions (individualized mPFC-ACC targeting; non-individualized MFC targeting; and a sham) in a double-blind cross-over study. Changes in the Visual Simon Task, Stop Signal Task, CPT III, and Stroop test were assessed before and after each session. Compared with non-individualized θ-tACS, the individualized HD θ-tACS significantly increased the number of interference words and the interference score in the Stroop test. The changes in the non-verbal cognitive tests did not induce a parallel effect. This is the first study to examine the influence of individualized HD θ-tACS targeted to the ACC on inhibitory control performance. The proposed algorithm represents a well-tolerated method that helps to improve the specificity of neuromodulation targeting of the ACC.
Collapse
Affiliation(s)
- Monika Klírová
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Veronika Voráčková
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Jiří Horáček
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Pavel Mohr
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Juraj Jonáš
- National Institute of Mental Health, Prague, Czechia
| | - Daniela Urbaczka Dudysová
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Lenka Kostýlková
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Dan Fayette
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | | | | | - Olga Laskov
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Tomáš Novák
- National Institute of Mental Health, Prague, Czechia
- Department of Psychiatry, Third Faculty of Medicine, Charles University, Prague, Czechia
| |
Collapse
|
13
|
Collavini S, Fernández-Corazza M, Oddo S, Princich JP, Kochen S, Muravchik CH. Improvements on spatial coverage and focality of deep brain stimulation in pre-surgical epilepsy mapping. J Neural Eng 2021; 18. [PMID: 33578398 DOI: 10.1088/1741-2552/abe5b9] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 02/12/2021] [Indexed: 12/20/2022]
Abstract
Objective.Electrical stimulation mapping (ESM) of the brain using stereo-electroencephalography (SEEG) intracranial electrodes, also known as depth-ESM (DESM), is being used as part of the pre-surgical planning for brain surgery in drug-resistant epilepsy patients. Typically, DESM consists in applying the electrical stimulation using adjacent contacts of the SEEG electrodes and in recording the EEG responses to those stimuli, giving valuable information of critical brain regions to better delimit the region to resect. However, the spatial extension or coverage of the stimulated area is not well defined even though the precise electrode locations can be determined from computed tomography images.Approach.We first conduct electrical simulations of DESM for different shapes of commercial SEEG electrodes showing the stimulation extensions for different intensities of injected current. We then evaluate the performance of DESM in terms of spatial coverage and focality on two realistic head models of real patients undergoing pre-surgical evaluation. We propose a novel strategy for DESM that consist in applying the current using contacts of different SEEG electrodes (x-DESM), increasing the versatility of DESM without implanting more electrodes. We also present a clinical case where x-DESM replicated the full semiology of an epilepsy seizure using a very low-intensity current injection, when typical adjacent DESM only reproduced partial symptoms with much larger intensities. Finally, we show one example of DESM optimal stimulation to achieve maximum intensity, maximum focality or intermediate solution at a pre-defined target, and one example of temporal interference in DESM capable of increasing focality in brain regions not immediately touching the electrode contacts.Main results.It is possible to define novel current injection patterns using contacts of different electrodes (x-DESM) that might improve coverage and/or focality, depending on the characteristics of the candidate brain. If individual simulations are not possible, we provide the estimated radius of stimulation as a function of the injected current and SEEG electrode brand as a reference for the community.Significance.Our results show that subject-specific electrical stimulations are a valuable tool to use in the pre-surgical planning to visualize the extension of the stimulated regions. The methods we present here are also applicable to pre-surgical planning of tumor resections and deep brain stimulation treatments.
Collapse
Affiliation(s)
- Santiago Collavini
- Research Institute of Electronics, Control and Signal Processing (LEICI), National University of La Plata-CONICET, Calle 116 s/n, La Plata B1900, Argentina.,Neurosciences and Complex Systems Unit (EnyS), CONICET, Hosp. El Cruce 'N. Kirchner', National University A. Jauretche (UNAJ), Calchaqui 5401, Florencio Varela 1888 Buenos Aires, Argentina.,National Council of Scientific and Technical Research (CONICET), calle 8, 1467, La Plata, Buenos Aires B1904, Argentina.,Institute of Engineering and Agronomy, National University Arturo Jauretche, Av. Calchaquí 6200, Florencio Varela, Buenos Aires 1888, Argentina
| | - Mariano Fernández-Corazza
- Research Institute of Electronics, Control and Signal Processing (LEICI), National University of La Plata-CONICET, Calle 116 s/n, La Plata B1900, Argentina.,National Council of Scientific and Technical Research (CONICET), calle 8, 1467, La Plata, Buenos Aires B1904, Argentina
| | - Silvia Oddo
- Neurosciences and Complex Systems Unit (EnyS), CONICET, Hosp. El Cruce 'N. Kirchner', National University A. Jauretche (UNAJ), Calchaqui 5401, Florencio Varela 1888 Buenos Aires, Argentina.,National Council of Scientific and Technical Research (CONICET), calle 8, 1467, La Plata, Buenos Aires B1904, Argentina
| | - Juan Pablo Princich
- Neurosciences and Complex Systems Unit (EnyS), CONICET, Hosp. El Cruce 'N. Kirchner', National University A. Jauretche (UNAJ), Calchaqui 5401, Florencio Varela 1888 Buenos Aires, Argentina.,National Council of Scientific and Technical Research (CONICET), calle 8, 1467, La Plata, Buenos Aires B1904, Argentina
| | - Silvia Kochen
- Neurosciences and Complex Systems Unit (EnyS), CONICET, Hosp. El Cruce 'N. Kirchner', National University A. Jauretche (UNAJ), Calchaqui 5401, Florencio Varela 1888 Buenos Aires, Argentina.,National Council of Scientific and Technical Research (CONICET), calle 8, 1467, La Plata, Buenos Aires B1904, Argentina
| | - Carlos H Muravchik
- Research Institute of Electronics, Control and Signal Processing (LEICI), National University of La Plata-CONICET, Calle 116 s/n, La Plata B1900, Argentina.,Scientific Research Commission of the Province of Buenos Aires (CIC-PBA), Argentina
| |
Collapse
|
14
|
van Bree S, Sohoglu E, Davis MH, Zoefel B. Sustained neural rhythms reveal endogenous oscillations supporting speech perception. PLoS Biol 2021; 19:e3001142. [PMID: 33635855 PMCID: PMC7946281 DOI: 10.1371/journal.pbio.3001142] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2020] [Revised: 03/10/2021] [Accepted: 02/08/2021] [Indexed: 12/23/2022] Open
Abstract
Rhythmic sensory or electrical stimulation will produce rhythmic brain responses. These rhythmic responses are often interpreted as endogenous neural oscillations aligned (or "entrained") to the stimulus rhythm. However, stimulus-aligned brain responses can also be explained as a sequence of evoked responses, which only appear regular due to the rhythmicity of the stimulus, without necessarily involving underlying neural oscillations. To distinguish evoked responses from true oscillatory activity, we tested whether rhythmic stimulation produces oscillatory responses which continue after the end of the stimulus. Such sustained effects provide evidence for true involvement of neural oscillations. In Experiment 1, we found that rhythmic intelligible, but not unintelligible speech produces oscillatory responses in magnetoencephalography (MEG) which outlast the stimulus at parietal sensors. In Experiment 2, we found that transcranial alternating current stimulation (tACS) leads to rhythmic fluctuations in speech perception outcomes after the end of electrical stimulation. We further report that the phase relation between electroencephalography (EEG) responses and rhythmic intelligible speech can predict the tACS phase that leads to most accurate speech perception. Together, we provide fundamental results for several lines of research-including neural entrainment and tACS-and reveal endogenous neural oscillations as a key underlying principle for speech perception.
Collapse
Affiliation(s)
- Sander van Bree
- MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom
- Centre for Cognitive Neuroimaging, University of Glasgow, Glasgow, United Kingdom
- School of Psychology and Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom
| | - Ediz Sohoglu
- MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom
- School of Psychology, University of Sussex, Brighton, United Kingdom
| | - Matthew H. Davis
- MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom
| | - Benedikt Zoefel
- MRC Cognition and Brain Sciences Unit, University of Cambridge, Cambridge, United Kingdom
- Centre de Recherche Cerveau et Cognition, CNRS, Toulouse, France
- Université Toulouse III Paul Sabatier, Toulouse, France
| |
Collapse
|
15
|
Voelker P, Parker AN, Luu P, Davey C, Rothbart MK, Posner MI. Increasing the amplitude of intrinsic theta in the human brain. AIMS Neurosci 2020; 7:418-437. [PMID: 33263079 PMCID: PMC7701373 DOI: 10.3934/neuroscience.2020026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 10/27/2020] [Indexed: 11/18/2022] Open
Abstract
In a mouse study we found increased myelination of pathways surrounding the anterior cingulate cortex (ACC) following stimulation near the theta rhythm (4-8 Hz), and evidence that this change in connectivity reduced behavioral anxiety. We cannot use the optogenetic methods with humans that were used in our mouse studies. This paper examines whether it is possible to enhance intrinsic theta amplitudes in humans using less invasive methods. The first experiment compares electrical, auditory and biofeedback as methods for increasing intrinsic theta rhythm amplitudes in the Anterior Cingulate Cortex (ACC). These methods are used alone or in conjunction with a task designed to activate the same area. The results favor using electrical stimulation in conjunction with a task targeting this region. Stimulating the ACC increases intrinsic theta more in this area than in a control area distant from the site of stimulation, suggesting some degree of localization of the stimulation. In Experiment 2, we employed electrical stimulation with the electrodes common to each person, or with electrodes selected from an individual head model. We targeted the ACC or Motor Cortex (PMC). At baseline, intrinsic theta is higher in the ACC than the PMC. In both areas, theta can be increased in amplitude by electrical stimulation plus task. In the PMC, theta levels during stimulation plus task are not significantly higher than during task alone. There is no significant difference between generic and individual electrodes. We discuss steps needed to determine whether we can use the electrical stimulation + task to improve the connectivity of white matter in different brain areas.
Collapse
Affiliation(s)
- Pascale Voelker
- Department of Psychology, University of Oregon, Eugene OR, USA
| | - Ashley N Parker
- Department of Psychology, University of Oregon, Eugene OR, USA
| | - Phan Luu
- Department of Psychology, University of Oregon, Eugene OR, USA
- BelCo Eugene OR, USA
| | | | - Mary K Rothbart
- Department of Psychology, University of Oregon, Eugene OR, USA
| | | |
Collapse
|
16
|
Fernandez-Corazza M, Turovets S, Muravchik CH. A novel bounded EIT protocol to generate inhomogeneous skull conductivity maps non-invasively. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2020:1440-1443. [PMID: 33018261 DOI: 10.1109/embc44109.2020.9175254] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Electrical Impedance Tomography (EIT) can be used to estimate the electrical properties of the head tissues in a parametric approach. This modality is called parametric EIT or bounded EIT (bEIT). Typical bEIT protocols alternate between several current injection patterns with two current injection electrodes each: one source and one sink ("1-to-1"), while the rest of the electrodes measure the resulting electric potential. Then, one value of conductivity per tissue (e.g. scalp and/or skull) is estimated independently for each current injection pair. With these protocols, it is difficult to obtain local estimates of the skull tissue. Thus, the grand average of the estimates obtained from each pair is assigned to each tissue modeling them as homogeneous. However, it is known that these tissues are inhomogeneous within the same subject. We propose the use of current injection patterns with one source and many sinks ("1to-N") located at the opposite side of the head to build individual and inhomogeneous skull conductivity maps. We validate the method with simulations and compare its performance with equivalent maps generated by using the classical "1-to-1" patterns. The map generated by the novel method shows better spatial correlation with the more conductive spongy bone presence.Clinical Relevance- The novel bEIT protocol allows to map individual head models with spatially resolved skull conductivities in vivo and non-invasively for use in electroencephalography (EEG) source localization, transcranial electrical stimulation (TES) dose calculations and TES pattern optimization, without the risk of ionizing radiation associated with computed tomography (CT) scans.
Collapse
|
17
|
Huang Y, Datta A, Parra LC. Optimization of interferential stimulation of the human brain with electrode arrays. J Neural Eng 2020; 17:036023. [PMID: 32403096 DOI: 10.1088/1741-2552/ab92b3] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Interferential stimulation (IFS) has generated considerable interest recently because of its potential to achieve focal electric fields in deep brain areas with transcranial currents. Conventionally, IFS applies sinusoidal currents through two electrode pairs with close-by frequencies. Here we propose to use an array of electrodes instead of just two electrode pairs; and to use algorithmic optimization to identify the currents required at each electrode to target a desired location in the brain. APPROACH We formulate rigorous optimization criteria for IFS to achieve either maximal modulation-depth or maximally focal stimulation. We find the solution for optimal modulation-depth analytically and maximize for focal stimulation numerically. MAIN RESULTS Maximal modulation is achieved when IFS equals conventional high-definition multi-electrode transcranial electrical stimulation (HD-TES) with a modulated current source. This optimal solution can be found directly from a current-flow model, i.e. the 'lead field' without the need for algorithmic optimization. Once currents are optimized numerically to achieve optimal focal stimulation, we find that IFS can indeed be more focal than conventional HD-TES, both at the cortical surface and deep in the brain. Generally, however, stimulation intensity of IFS is weak and the locus of highest intensity does not match the locus of highest modulation. SIGNIFICANCE This proof-of-principle study shows the potential of IFS over HD-TES for focal non-invasive deep brain stimulation. Future work will be needed to improve on intensity of stimulation and convergence of the optimization procedure.
Collapse
Affiliation(s)
- Yu Huang
- Department of Biomedical Engineering, City College of the City University of New York, New York, NY, 10031 United States of America. Research & Development, Soterix Medical, Inc., New York, NY, 10001 United States of America. Author to whom any correspondence should be addressed
| | | | | |
Collapse
|
18
|
Khan A, Haueisen J, Wolters CH, Antonakakis M, Vogenauer N, Wollbrink A, Suntrup-Krueger S, Schneider TR, Herrmann CS, Nitsche M, Paulus W. Constrained maximum intensity optimized multi-electrode tDCS targeting of human somatosensory network. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2020; 2019:5894-5897. [PMID: 31947191 DOI: 10.1109/embc.2019.8857253] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Transcranial direct current stimulation (tDCS) is a noninvasive method that delivers current through the scalp to enhance or suppress brain activity. The standard way of applying tDCS is by the use of two large rectangular sponge electrodes on the scalp. The resulting currents often stimulate a broad region of the brain distributed over brain networks. In order to address this issue, recently, multi-electrode transcranial direct current stimulation with optimized montages has been used to stimulate brain regions of interest (ROI) with improved trade-off between focality and intensity of the electrical current at the target brain region. However, in many cases only the location of target region is considered and not the orientation. Here we emphasize the importance of calculating the individualized target location and orientation by combined electroencephalography and magnetoencephalography (EMEG) source analysis in individualized skull-conductivity calibrated finite element method (FEM) head models and stimulate the target region by four different tDCS montages. We have chosen the generator of the P20/N20 component, located at Brodmann area 3b and oriented mainly from posterior to anterior directions as our target for stimulation because it can be modeled as a single dipole source with a fixed position and orientation. The simulations will deliver optimized excitatory and inhibitory electrode montages that are in future investigations compared to standard and sham tDCS in a somatosensory experiment. We also present a new constrained maximum intensity (CMI) optimization approach that better distributes the currents over multiple electrodes, therefore should lead to less tingling and burning sensations at the skin, and thus allows an easier realization of the sham condition significantly reducing the current intensity parallel to the target.
Collapse
|
19
|
Fernández-Corazza M, Turovets S, Muravchik CH. Unification of optimal targeting methods in transcranial electrical stimulation. Neuroimage 2019; 209:116403. [PMID: 31862525 PMCID: PMC7110419 DOI: 10.1016/j.neuroimage.2019.116403] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Revised: 11/11/2019] [Accepted: 11/24/2019] [Indexed: 12/22/2022] Open
Abstract
One of the major questions in high-density transcranial electrical stimulation (TES) is: given a region of interest (ROI) and electric current limits for safety, how much current should be delivered by each electrode for optimal targeting of the ROI? Several solutions, apparently unrelated, have been independently proposed depending on how "optimality" is defined and on how this optimization problem is stated mathematically. The least squares (LS), weighted LS (WLS), or reciprocity-based approaches are the simplest ones and have closed-form solutions. An extended optimization problem can be stated as follows: maximize the directional intensity at the ROI, limit the electric fields at the non-ROI, and constrain total injected current and current per electrode for safety. This problem requires iterative convex or linear optimization solvers. We theoretically prove in this work that the LS, WLS and reciprocity-based closed-form solutions are specific solutions to the extended directional maximization optimization problem. Moreover, the LS/WLS and reciprocity-based solutions are the two extreme cases of the intensity-focality trade-off, emerging under variation of a unique parameter of the extended directional maximization problem, the imposed constraint to the electric fields at the non-ROI. We validate and illustrate these findings with simulations on an atlas head model. The unified approach we present here allows a better understanding of the nature of the TES optimization problem and helps in the development of advanced and more effective targeting strategies.
Collapse
Affiliation(s)
- Mariano Fernández-Corazza
- LEICI Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales, Universidad Nacional de La Plata, CONICET, Argentina.
| | - Sergei Turovets
- NeuroInformatics Center, University of Oregon, Eugene, OR, USA
| | - Carlos Horacio Muravchik
- LEICI Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales, Universidad Nacional de La Plata, CONICET, Argentina; Comisión de Investigaciones Científicas, CICPBA, Provincia de Buenos Aires, Argentina
| |
Collapse
|
20
|
Holmes MD, Feng R, Wise MV, Ma C, Ramon C, Wu J, Luu P, Hou J, Pan L, Tucker DM. Safety of slow-pulsed transcranial electrical stimulation in acute spike suppression. Ann Clin Transl Neurol 2019; 6:2579-2585. [PMID: 31709777 PMCID: PMC6917336 DOI: 10.1002/acn3.50934] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Revised: 10/07/2019] [Accepted: 10/09/2019] [Indexed: 11/12/2022] Open
Abstract
We examined the effects of slow‐pulsed transcranial electrical stimulation (TES) in suppressing epileptiform discharges in seven adults with refractory epilepsy. An MRI‐based realistic head model was constructed for each subject and co‐registered with 256‐channel dense EEG (dEEG). Interictal spikes were localized, and TES targeted the cortical source of each subject's principal spike population. Targeted spikes were suppressed in five subject's (29/35 treatment days overall), and nontargeted spikes were suppressed in four subjects. Epileptiform activity did not worsen. This study suggests that this protocol, designed to induce long‐term depression (LTD), is safe and effective in acute suppression of interictal epileptiform discharges.
Collapse
Affiliation(s)
- Mark D Holmes
- Regional Epilepsy Center, Department of Neurology, University of Washington, Seattle, Washington
| | - Rui Feng
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Mackenzie V Wise
- Regional Epilepsy Center, Department of Neurology, University of Washington, Seattle, Washington
| | - Chengxin Ma
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Ceon Ramon
- Regional Epilepsy Center, Department of Neurology, University of Washington, Seattle, Washington.,Department of Electrical Engineering, University of Washington, Seattle, Washington
| | - Jinsong Wu
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Phan Luu
- Brain Electrophysiology Laboratory Company, Eugene, Oregon
| | | | - Li Pan
- Department of Neurosurgery, Huashan Hospital, Fudan University, Shanghai, China
| | - Don M Tucker
- Brain Electrophysiology Laboratory Company, Eugene, Oregon
| |
Collapse
|
21
|
Chen L, Zou X, Tang R, Ke A, He J. Effect of electrode-electrolyte spatial mismatch on transcranial direct current stimulation: a finite element modeling study. J Neural Eng 2019; 16:056012. [DOI: 10.1088/1741-2552/ab29c5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
22
|
Seo H, Jun SC. Relation between the electric field and activation of cortical neurons in transcranial electrical stimulation. Brain Stimul 2019; 12:275-289. [DOI: 10.1016/j.brs.2018.11.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 10/03/2018] [Accepted: 11/06/2018] [Indexed: 12/12/2022] Open
|
23
|
Wang Y, Zhou H, Li Y, Liu W. Impact of Electrode Number on the Performance of High-Definition Transcranial Direct Current Stimulation (HD-tDCS). ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2018; 2018:4182-4185. [PMID: 30441277 DOI: 10.1109/embc.2018.8513379] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation for treating brain disorders by applying constant current through scalp towards the targeted cortex regions. Precisely activating or inhibiting a specific area without interfering other parts in the brain is a challenge of tDCS. Recently high-definition tDCS (HD-tDCS) with optimization technique attracts a lot of attention due to the improved focality. Unlike conventional tDCS which utilizes two large pads to deliver current to certain area, HD-tDCS employs tens of smaller electrodes. The purpose of this work is to study the effect of the electrode number on the performance of HD-tDCS. A realistic head model with four layers of tissue was constructed with different electrode montages. A systematic simulation study was conducted using targets in different regions with different functions to analyze the focusing capability, stimulation accuracy, and the intensity of constrained least square based optimized HD-tDCS. Results show that better performance in all three aspects can be achieved by increasing the electrode number.
Collapse
|
24
|
Gebodh N, Esmaeilpour Z, Adair D, Chelette K, Dmochowski J, Woods AJ, Kappenman ES, Parra LC, Bikson M. Inherent physiological artifacts in EEG during tDCS. Neuroimage 2018; 185:408-424. [PMID: 30321643 DOI: 10.1016/j.neuroimage.2018.10.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Revised: 09/10/2018] [Accepted: 10/08/2018] [Indexed: 12/30/2022] Open
Abstract
Online imaging and neuromodulation is invalid if stimulation distorts measurements beyond the point of accurate measurement. In theory, combining transcranial Direct Current Stimulation (tDCS) with electroencephalography (EEG) is compelling, as both use non-invasive electrodes and image-guided dose can be informed by the reciprocity principle. To distinguish real changes in EEG from stimulation artifacts, prior studies applied conventional signal processing techniques (e.g. high-pass filtering, ICA). Here, we address the assumptions underlying the suitability of these approaches. We distinguish physiological artifacts - defined as artifacts resulting from interactions between the stimulation induced voltage and the body and so inherent regardless of tDCS or EEG hardware performance - from methodology-related artifacts - arising from non-ideal experimental conditions or non-ideal stimulation and recording equipment performance. Critically, we identify inherent physiological artifacts which are present in all online EEG-tDCS: 1) cardiac distortion and 2) ocular motor distortion. In conjunction, non-inherent physiological artifacts which can be minimized in most experimental conditions include: 1) motion and 2) myogenic distortion. Artifact dynamics were analyzed for varying stimulation parameters (montage, polarity, current) and stimulation hardware. Together with concurrent physiological monitoring (ECG, respiration, ocular, EMG, head motion), and current flow modeling, each physiological artifact was explained by biological source-specific body impedance changes, leading to incremental changes in scalp DC voltage that are significantly larger than real neural signals. Because these artifacts modulate the DC voltage and scale with applied current, they are dose specific such that their contamination cannot be accounted for by conventional experimental controls (e.g. differing stimulation montage or current as a control). Moreover, because the EEG artifacts introduced by physiologic processes during tDCS are high dimensional (as indicated by Generalized Singular Value Decomposition- GSVD), non-stationary, and overlap highly with neurogenic frequencies, these artifacts cannot be easily removed with conventional signal processing techniques. Spatial filtering techniques (GSVD) suggest that the removal of physiological artifacts would significantly degrade signal integrity. Physiological artifacts, as defined here, would emerge only during tDCS, thus processing techniques typically applied to EEG in the absence of tDCS would not be suitable for artifact removal during tDCS. All concurrent EEG-tDCS must account for physiological artifacts that are a) present regardless of equipment used, and b) broadband and confound a broad range of experiments (e.g. oscillatory activity and event related potentials). Removal of these artifacts requires the recognition of their non-stationary, physiology-specific dynamics, and individualized nature. We present a broad taxonomy of artifacts (non/stimulation related), and suggest possible approaches and challenges to denoising online EEG-tDCS stimulation artifacts.
Collapse
Affiliation(s)
- Nigel Gebodh
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of the City University of New York, New York, NY, USA.
| | - Zeinab Esmaeilpour
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of the City University of New York, New York, NY, USA.
| | - Devin Adair
- Department of Psychology, The Graduate Center at City University of New York, New York, NY, USA.
| | | | - Jacek Dmochowski
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of the City University of New York, New York, NY, USA.
| | - Adam J Woods
- Center for Cognitive Aging and Memory, McKnight Brain Institute, Department of Clinical and Health Psychology, Department of Neuroscience, University of Florida, Gainesville, FL, USA.
| | | | - Lucas C Parra
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of the City University of New York, New York, NY, USA.
| | - Marom Bikson
- Neural Engineering Laboratory, Department of Biomedical Engineering, The City College of New York of the City University of New York, New York, NY, USA; Department of Psychology, The Graduate Center at City University of New York, New York, NY, USA.
| |
Collapse
|
25
|
Skull Modeling Effects in Conductivity Estimates Using Parametric Electrical Impedance Tomography. IEEE Trans Biomed Eng 2018; 65:1785-1797. [DOI: 10.1109/tbme.2017.2777143] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
26
|
Bikson M, Brunoni AR, Charvet LE, Clark VP, Cohen LG, Deng ZD, Dmochowski J, Edwards DJ, Frohlich F, Kappenman ES, Lim KO, Loo C, Mantovani A, McMullen DP, Parra LC, Pearson M, Richardson JD, Rumsey JM, Sehatpour P, Sommers D, Unal G, Wassermann EM, Woods AJ, Lisanby SH. Rigor and reproducibility in research with transcranial electrical stimulation: An NIMH-sponsored workshop. Brain Stimul 2018; 11:465-480. [PMID: 29398575 PMCID: PMC5997279 DOI: 10.1016/j.brs.2017.12.008] [Citation(s) in RCA: 123] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 12/01/2017] [Accepted: 12/21/2017] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND Neuropsychiatric disorders are a leading source of disability and require novel treatments that target mechanisms of disease. As such disorders are thought to result from aberrant neuronal circuit activity, neuromodulation approaches are of increasing interest given their potential for manipulating circuits directly. Low intensity transcranial electrical stimulation (tES) with direct currents (transcranial direct current stimulation, tDCS) or alternating currents (transcranial alternating current stimulation, tACS) represent novel, safe, well-tolerated, and relatively inexpensive putative treatment modalities. OBJECTIVE This report seeks to promote the science, technology and effective clinical applications of these modalities, identify research challenges, and suggest approaches for addressing these needs in order to achieve rigorous, reproducible findings that can advance clinical treatment. METHODS The National Institute of Mental Health (NIMH) convened a workshop in September 2016 that brought together experts in basic and human neuroscience, electrical stimulation biophysics and devices, and clinical trial methods to examine the physiological mechanisms underlying tDCS/tACS, technologies and technical strategies for optimizing stimulation protocols, and the state of the science with respect to therapeutic applications and trial designs. RESULTS Advances in understanding mechanisms, methodological and technological improvements (e.g., electronics, computational models to facilitate proper dosing), and improved clinical trial designs are poised to advance rigorous, reproducible therapeutic applications of these techniques. A number of challenges were identified and meeting participants made recommendations made to address them. CONCLUSIONS These recommendations align with requirements in NIMH funding opportunity announcements to, among other needs, define dosimetry, demonstrate dose/response relationships, implement rigorous blinded trial designs, employ computational modeling, and demonstrate target engagement when testing stimulation-based interventions for the treatment of mental disorders.
Collapse
Affiliation(s)
- Marom Bikson
- Department of Biomedical Engineering, The City College of the City University of New York, United States
| | - Andre R Brunoni
- Laboratory of Neurosciences (LIM-27), Department and Institute of Psychiatry, University of Sao Paulo, Sao Paulo, Brazil
| | - Leigh E Charvet
- Department of Neurology, New York University School of Medicine, New York, NY, United States
| | - Vincent P Clark
- Department of Psychology, University of New Mexico, Albuquerque, NM, United States
| | - Leonardo G Cohen
- Human Cortical Physiology and Neurorehabilitation Section, National Institute of Neurological Disorders and Stroke, Bethesda, MD, United States
| | - Zhi-De Deng
- Experimental Therapeutics and Pathophysiology Branch, National Institute of Mental Health, Bethesda, MD, United States
| | - Jacek Dmochowski
- Department of Biomedical Engineering, The City College of the City University of New York, United States
| | - Dylan J Edwards
- Non-invasive Brain Stimulation and Human Motor Control Laboratory, Burke Rehabilitation and Research, Burke-Cornell Medical Research Facility, White Plains, New York and School of Medicine and Health Sciences, Edith Cowan University, Perth, Australia
| | - Flavio Frohlich
- Department of Psychiatry, Cell Biology and Physiology, Biomedical Engineering, and Neurology, Carolina Center for Neurostimulation, University of North Carolina School of Medicine, Chapel Hill, NC, United States
| | - Emily S Kappenman
- Department of Psychology, San Diego State University, San Diego, CA, United States
| | - Kelvin O Lim
- Department of Psychiatry, University of Minnesota, Minneapolis Veterans Administration Health Care System, and Defense Veterans Brain Injury Center, Minneapolis, MN, United States
| | - Colleen Loo
- School of Psychiatry and Black Dog Institute, University of New South Wales, Sydney, Australia
| | - Antonio Mantovani
- Department of Physiology, Pharmacology and Neuroscience, City College of the City University of New York, New York, NY, United States
| | - David P McMullen
- Division of Translational Research, National Institute of Mental Health, Bethesda, MD, United States
| | - Lucas C Parra
- Department of Biomedical Engineering, The City College of the City University of New York, United States
| | - Michele Pearson
- Division of Translational Research, National Institute of Mental Health, Bethesda, MD, United States
| | - Jessica D Richardson
- Department of Speech and Hearing Sciences, University of New Mexico, Albuquerque, NM, United States
| | - Judith M Rumsey
- Division of Translational Research, National Institute of Mental Health, Bethesda, MD, United States.
| | - Pejman Sehatpour
- Department of Psychiatry, Columbia University, New York, NY, United States
| | - David Sommers
- Scientific Review Branch, National Institute of Mental Health, Bethesda, MD, United States
| | - Gozde Unal
- Department of Biomedical Engineering, The City College of the City University of New York, United States
| | - Eric M Wassermann
- Behavioral Neurology Unit, National Institute of Neurological Disorders and Stroke, Bethesda, MD, United States
| | - Adam J Woods
- Department of Clinical and Health Psychology, Center for Cognitive Aging and Memory, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
| | - Sarah H Lisanby
- Division of Translational Research, National Institute of Mental Health, Bethesda, MD, United States
| |
Collapse
|
27
|
Halpern CH, Miller KJ, Wu H, Tass PA. Letter: Electric Beats Open New Frontiers for Deep Brain Stimulation. Neurosurgery 2017; 82:E19-E20. [DOI: 10.1093/neuros/nyx482] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
|
28
|
Dmochowski JP, Koessler L, Norcia AM, Bikson M, Parra LC. Optimal use of EEG recordings to target active brain areas with transcranial electrical stimulation. Neuroimage 2017; 157:69-80. [PMID: 28578130 PMCID: PMC5777160 DOI: 10.1016/j.neuroimage.2017.05.059] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 05/11/2017] [Accepted: 05/27/2017] [Indexed: 12/14/2022] Open
Abstract
To demonstrate causal relationships between brain and behavior, investigators would like to guide brain stimulation using measurements of neural activity. Particularly promising in this context are electroencephalography (EEG) and transcranial electrical stimulation (TES), as they are linked by a reciprocity principle which, despite being known for decades, has not led to a formalism for relating EEG recordings to optimal stimulation parameters. Here we derive a closed-form expression for the TES configuration that optimally stimulates (i.e., targets) the sources of recorded EEG, without making assumptions about source location or distribution. We also derive a duality between TES targeting and EEG source localization, and demonstrate that in cases where source localization fails, so does the proposed targeting. Numerical simulations with multiple head models confirm these theoretical predictions and quantify the achieved stimulation in terms of focality and intensity. We show that constraining the stimulation currents automatically selects optimal montages that involve only a few (4-7) electrodes, with only incremental loss in performance when targeting focal activations. The proposed technique allows brain scientists and clinicians to rationally target the sources of observed EEG and thus overcomes a major obstacle to the realization of individualized or closed-loop brain stimulation.
Collapse
Affiliation(s)
- Jacek P Dmochowski
- Department of Biomedical Engineering, Steinman Hall 460 City College of New York, New York, NY 10031, USA.
| | | | | | | | | |
Collapse
|
29
|
Luu P, Essaki Arumugam EM, Anderson E, Gunn A, Rech D, Turovets S, Tucker DM. Slow-Frequency Pulsed Transcranial Electrical Stimulation for Modulation of Cortical Plasticity Based on Reciprocity Targeting with Precision Electrical Head Modeling. Front Hum Neurosci 2016. [PMID: 27531976 DOI: 10.3339/fnhum.2016.00377] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
In pain management as well as other clinical applications of neuromodulation, it is important to consider the timing parameters influencing activity-dependent plasticity, including pulsed versus sustained currents, as well as the spatial action of electrical currents as they polarize the complex convolutions of the cortical mantle. These factors are of course related; studying temporal factors is not possible when the spatial resolution of current delivery to the cortex is so uncertain to make it unclear whether excitability is increased or decreased with anodal vs. cathodal current flow. In the present study we attempted to improve the targeting of specific cortical locations by applying current through flexible source-sink configurations of 256 electrodes in a geodesic array. We constructed a precision electric head model for 12 healthy individuals. Extraction of the individual's cortical surface allowed computation of the component of the induced current that is normal to the target cortical surface. In an effort to replicate the long-term depression (LTD) induced with pulsed protocols in invasive animal research and transcranial magnetic stimulation studies, we applied 100 ms pulses at 1.9 s intervals either in cortical-surface-anodal or cortical-surface-cathodal directions, with a placebo (sham) control. The results showed significant LTD of the motor evoked potential as a result of the cortical-surface-cathodal pulses in contrast to the placebo control, with a smaller but similar LTD effect for anodal pulses. The cathodal LTD after-effect was sustained over 90 min following current injection. These results support the feasibility of pulsed protocols with low total charge in non-invasive neuromodulation when the precision of targeting is improved with a dense electrode array and accurate head modeling.
Collapse
Affiliation(s)
- Phan Luu
- Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA
| | | | | | | | | | - Sergei Turovets
- Electrical Geodesics, Inc., EugeneOR, USA; NeuroInformatics Center, University of Oregon, EugeneOR, USA
| | - Don M Tucker
- Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA
| |
Collapse
|
30
|
Luu P, Essaki Arumugam EM, Anderson E, Gunn A, Rech D, Turovets S, Tucker DM. Slow-Frequency Pulsed Transcranial Electrical Stimulation for Modulation of Cortical Plasticity Based on Reciprocity Targeting with Precision Electrical Head Modeling. Front Hum Neurosci 2016; 10:377. [PMID: 27531976 PMCID: PMC4969286 DOI: 10.3389/fnhum.2016.00377] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Accepted: 07/12/2016] [Indexed: 12/16/2022] Open
Abstract
In pain management as well as other clinical applications of neuromodulation, it is important to consider the timing parameters influencing activity-dependent plasticity, including pulsed versus sustained currents, as well as the spatial action of electrical currents as they polarize the complex convolutions of the cortical mantle. These factors are of course related; studying temporal factors is not possible when the spatial resolution of current delivery to the cortex is so uncertain to make it unclear whether excitability is increased or decreased with anodal vs. cathodal current flow. In the present study we attempted to improve the targeting of specific cortical locations by applying current through flexible source-sink configurations of 256 electrodes in a geodesic array. We constructed a precision electric head model for 12 healthy individuals. Extraction of the individual's cortical surface allowed computation of the component of the induced current that is normal to the target cortical surface. In an effort to replicate the long-term depression (LTD) induced with pulsed protocols in invasive animal research and transcranial magnetic stimulation studies, we applied 100 ms pulses at 1.9 s intervals either in cortical-surface-anodal or cortical-surface-cathodal directions, with a placebo (sham) control. The results showed significant LTD of the motor evoked potential as a result of the cortical-surface-cathodal pulses in contrast to the placebo control, with a smaller but similar LTD effect for anodal pulses. The cathodal LTD after-effect was sustained over 90 min following current injection. These results support the feasibility of pulsed protocols with low total charge in non-invasive neuromodulation when the precision of targeting is improved with a dense electrode array and accurate head modeling.
Collapse
Affiliation(s)
- Phan Luu
- Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA
| | | | | | | | | | - Sergei Turovets
- Electrical Geodesics, Inc., EugeneOR, USA; NeuroInformatics Center, University of Oregon, EugeneOR, USA
| | - Don M Tucker
- Electrical Geodesics, Inc., EugeneOR, USA; Department of Psychology, University of Oregon, EugeneOR, USA
| |
Collapse
|