title: What is the optimal anodal electrode position for inducing corticomotor excitability changes in transcranial direct current stimulation?
abstract: Transcranial direct current stimulation (tDCS) non-invasively modulates brain function by inducing neuronal excitability. The conventional hot spot for inducing the highest current density in the hand motor area may not be the optimal site for effective stimulation. In this study, we investigated the influence of the center position of the anodal electrode on changes in motor cortical excitability. We considered three tDCS conditions in 16 healthy subjects: (i) real stimulation with the anodal electrode located at the conventional hand motor hot spot determined by motor evoked potentials (MEPs); (ii) real stimulation with the anodal electrode located at the point with the highest current density in the hand motor area as determined by electric current simulation; and (iii) sham stimulation. Motor cortical excitability as measured by MEP amplitude increased after both real stimulation conditions, but not after sham stimulation. Stimulation using the simulation-derived anodal electrode position, which was found to be posterior to the MEP hot spot for all subjects, induced higher motor cortical excitability. Individual positioning of the anodal electrode, based on the consideration of anatomical differences between subjects, appears to be important for maximizing the effects of tDCS.
authors.affiliation: Department of Health Sciences and Technology, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea. Electronic address: minji.lee@skku.edu.
authors.forename: Minji
authors.initials: M
authors.lastname: Lee
authors.affiliation: Department of Health Sciences and Technology, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea; Department of Physical and Rehabilitation Medicine, Center for Prevention & Rehabilitation, Heart Vascular and Stroke, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea. Electronic address: yun1225.kim@samsung.com.
authors.forename: Yun-Hee
authors.initials: YH
authors.lastname: Kim
authors.affiliation: Department of Biomedical Engineering, Hanyang University, Haengdang 1-dong, Seongdong-gu, Seoul 133-791, Republic of Korea. Electronic address: ich@hanyang.ac.kr.
authors.forename: Chang-Hwan
authors.initials: CH
authors.lastname: Im
authors.affiliation: Department of Biomedical Engineering, Hanyang University, Haengdang 1-dong, Seongdong-gu, Seoul 133-791, Republic of Korea. Electronic address: gmsinhwa@naver.com.
authors.forename: Jung-Hoon
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Physical and Rehabilitation Medicine, Center for Prevention & Rehabilitation, Heart Vascular and Stroke, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea. Electronic address: park.changhyun@hanmail.net.
authors.forename: Chang-hyun
authors.initials: CH
authors.lastname: Park
authors.affiliation: Department of Physical and Rehabilitation Medicine, Center for Prevention & Rehabilitation, Heart Vascular and Stroke, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea. Electronic address: wh.chang@samsung.com.
authors.forename: Won Hyuk
authors.initials: WH
authors.lastname: Chang
authors.affiliation: Department of Health Sciences and Technology, Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, 50 Irwon-dong, Gangnam-gu, Seoul 135-710, Republic of Korea. Electronic address: ahee.lee@gmail.com.
authors.forename: Ahee
authors.initials: A
authors.lastname: Lee
mesh_terms: D000328:Adult; D002540:Cerebral Cortex / Q000502:physiology*; D018592:Cross-Over Studies; D004566:Electrodes; D019054:Evoked Potentials, Motor; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D016037:Single-Blind Method; D065908:Transcranial Direct Current Stimulation / Q000295:instrumentation / Q000379:methods*; D050781:Transcranial Magnetic Stimulation
keywords: Electric current density; Motor cortical excitability; Transcranial direct current stimulation (tDCS)