title: Inconsistent outcomes of transcranial direct current stimulation may originate from anatomical differences among individuals: electric field simulation using individual MRI data.
abstract: Transcranial direct current stimulation (tDCS) is a neuromodulation protocol that can facilitate or inhibit cortical excitability in particular areas of the brain. Although recent studies have reported that tDCS can successfully modulate the excitability of various brain sites, outcomes of tDCS were not consistent between subjects even when identical stimulation protocols were applied. Thus far, however, no studies have clearly verified the main cause of this individual variability. In this study, the main hypothesis was that individual variability in tDCS effects might be partly explained by anatomical differences among subjects. To verify our hypothesis, we investigated the relationship between the behavioral outcomes of a verbal working memory (WM) task and current density values at the dorsolateral prefrontal cortex (DLPFC) simulated using the finite element method (FEM). A 3-back verbal working memory task experiment was conducted in 17 healthy subjects before and after tDCS with cathode and anode electrodes located at the right supraorbital and F3 locations, respectively. The results showed that participants who showed evidence of enhanced WM task performance after tDCS had a significantly larger current density at the DLPFC than other participants, suggesting that inconsistent behavioral outcomes of tDCS might be partly due to individual anatomical differences.
authors: Department of Biomedical Engineering, Hanyang University, Seoul, South Korea.
authors: Jung-Hoon
authors: JH
authors: Kim
authors: Department of Biomedical Engineering, Hanyang University, Seoul, South Korea.
authors: Do-Won
authors: DW
authors: Kim
authors: Department of Physical and Rehabilitation Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors: Won Hyuk
authors: WH
authors: Chang
authors: Department of Physical and Rehabilitation Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, South Korea.
authors: Yun-Hee
authors: YH
authors: Kim
authors: Korea Research Institute of Standard and Science (KRISS), Daejeon, South Korea.
authors: Kiwoong
authors: K
authors: Kim
authors: Department of Biomedical Engineering, Hanyang University, Seoul, South Korea. Electronic address: ich@hanyang.ac.kr.
authors: Chang-Hwan
authors: CH
authors: Im
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology; D017397:Prefrontal Cortex / Q000033:anatomy & histology* / Q000502:physiology*; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Dorsolateral prefrontal cortex (DLPFC); Finite element method; Transcranial direct current stimulation (tDCS); Working memory task