Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation
<b>Background:</b> In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purp...
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MDPI AG
2021-09-01
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| Series: | Journal of Personalized Medicine |
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| Online Access: | https://www.mdpi.com/2075-4426/11/9/940 |
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| author | Rajan Kashyap Sagarika Bhattacharjee Ramaswamy Arumugam Rose Dawn Bharath Kaviraja Udupa Kenichi Oishi John E. Desmond S. H. Annabel Chen Cuntai Guan |
| author_facet | Rajan Kashyap Sagarika Bhattacharjee Ramaswamy Arumugam Rose Dawn Bharath Kaviraja Udupa Kenichi Oishi John E. Desmond S. H. Annabel Chen Cuntai Guan |
| author_sort | Rajan Kashyap |
| collection | DOAJ |
| description | <b>Background:</b> In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. <b>Aim:</b> To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. <b>Method:</b> Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the dose. We estimated the variation of DTDI within and across individuals using T1-weighted brain images of 45 males and females distributed equally across three age groups: (a) young adults (20 ≤ x ˂ 40 years), (b) mid adults (40 ≤ x ˂ 60 years), and (c) older adults (60 ≤ x ˂ 80 years). DTDI’s were evaluated for the frontal montage with electrodes at F3 and the right supraorbital for three current doses of 1 mA, 2 mA, and 3 mA, with the target ROI at the left middle frontal gyrus. <b>Result:</b> As the dose is incremented, DTDI may show (a) increase, (b) decrease, and (c) no change across the individuals depending on the relationship (nonlinear or linear) between the injected tDCS current and the distribution of current density in the target ROI. The nonlinearity is predominant in older adults with a decrease in focality. The decline is stronger in males. Higher current dose at older age can enhance the focality of stimulation. <b>Conclusion:</b> DTDI provides information on which tDCS current dose will optimize the focality of stimulation. The recommended DTDI dose should be prioritized based on the age (>40 years) and sex (especially for males) of an individual. The toolbox i-SATA(MNI) is freely available. |
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| spelling | doaj.art-9ded9b2379d149f5b75ca1d738943fe62023-11-22T13:51:27ZengMDPI AGJournal of Personalized Medicine2075-44262021-09-0111994010.3390/jpm11090940Focality-Oriented Selection of Current Dose for Transcranial Direct Current StimulationRajan Kashyap0Sagarika Bhattacharjee1Ramaswamy Arumugam2Rose Dawn Bharath3Kaviraja Udupa4Kenichi Oishi5John E. Desmond6S. H. Annabel Chen7Cuntai Guan8School of Computer Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, SingaporeSchool of Social Sciences (SSS), Nanyang Technological University, Singapore 639818, SingaporeSchool of Computer Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, SingaporeDepartment of Neuroimaging and Interventional Radiology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560029, IndiaDepartment of Neurophysiology, National Institute of Mental Health and Neurosciences, Hosur Road, Bangalore 560029, IndiaThe Johns Hopkins University School of Medicine, Baltimore, MD 21205, USAThe Johns Hopkins University School of Medicine, Baltimore, MD 21205, USASchool of Social Sciences (SSS), Nanyang Technological University, Singapore 639818, SingaporeSchool of Computer Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore<b>Background:</b> In transcranial direct current stimulation (tDCS), the injected current becomes distributed across the brain areas. The objective is to stimulate the target region of interest (ROI) while minimizing the current in non-target ROIs (the ‘focality’ of tDCS). For this purpose, determining the appropriate current dose for an individual is difficult. <b>Aim:</b> To introduce a dose–target determination index (DTDI) to quantify the focality of tDCS and examine the dose–focality relationship in three different populations. <b>Method:</b> Here, we extended our previous toolbox i-SATA to the MNI reference space. After a tDCS montage is simulated for a current dose, the i-SATA(MNI) computes the average (over voxels) current density for every region in the brain. DTDI is the ratio of the average current density at the target ROI to the ROI with a maximum value (the peak region). Ideally, target ROI should be the peak region, so DTDI shall range from 0 to 1. The higher the value, the better the dose. We estimated the variation of DTDI within and across individuals using T1-weighted brain images of 45 males and females distributed equally across three age groups: (a) young adults (20 ≤ x ˂ 40 years), (b) mid adults (40 ≤ x ˂ 60 years), and (c) older adults (60 ≤ x ˂ 80 years). DTDI’s were evaluated for the frontal montage with electrodes at F3 and the right supraorbital for three current doses of 1 mA, 2 mA, and 3 mA, with the target ROI at the left middle frontal gyrus. <b>Result:</b> As the dose is incremented, DTDI may show (a) increase, (b) decrease, and (c) no change across the individuals depending on the relationship (nonlinear or linear) between the injected tDCS current and the distribution of current density in the target ROI. The nonlinearity is predominant in older adults with a decrease in focality. The decline is stronger in males. Higher current dose at older age can enhance the focality of stimulation. <b>Conclusion:</b> DTDI provides information on which tDCS current dose will optimize the focality of stimulation. The recommended DTDI dose should be prioritized based on the age (>40 years) and sex (especially for males) of an individual. The toolbox i-SATA(MNI) is freely available.https://www.mdpi.com/2075-4426/11/9/940transcranial direct current stimulation (tDCS)realistic volumetric approach-based simulator for transcranial electric stimulation (ROAST)systematic approach for tDCS analysis (SATA)current doseindividualized tDCSage and sex difference |
| spellingShingle | Rajan Kashyap Sagarika Bhattacharjee Ramaswamy Arumugam Rose Dawn Bharath Kaviraja Udupa Kenichi Oishi John E. Desmond S. H. Annabel Chen Cuntai Guan Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation Journal of Personalized Medicine transcranial direct current stimulation (tDCS) realistic volumetric approach-based simulator for transcranial electric stimulation (ROAST) systematic approach for tDCS analysis (SATA) current dose individualized tDCS age and sex difference |
| title | Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation |
| title_full | Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation |
| title_fullStr | Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation |
| title_full_unstemmed | Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation |
| title_short | Focality-Oriented Selection of Current Dose for Transcranial Direct Current Stimulation |
| title_sort | focality oriented selection of current dose for transcranial direct current stimulation |
| topic | transcranial direct current stimulation (tDCS) realistic volumetric approach-based simulator for transcranial electric stimulation (ROAST) systematic approach for tDCS analysis (SATA) current dose individualized tDCS age and sex difference |
| url | https://www.mdpi.com/2075-4426/11/9/940 |
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