brain sciences Article Null Effect of Transcranial Static Magnetic Field Stimulation over the Dorsolateral Prefrontal Cortex on Behavioral Performance in a Go/NoGo Task Tatsunori Watanabe 1 , Nami Kubo 1 , Xiaoxiao Chen 1 , Keisuke Yunoki 1 , Takuya Matsumoto 1,2 , Takayuki Kuwabara 1 , Toru Sunagawa 3 , Shota Date 3 , Tatsuya Mima 4 and Hikari Kirimoto 1, *   Citation: Watanabe, T.; Kubo, N.; Chen, X.; Yunoki, K.; Matsumoto, T.; Kuwabara, T.; Sunagawa, T.; Date, S.; Mima, T.; Kirimoto, H. Null Effect of Transcranial Static Magnetic Field Stimulation over the Dorsolateral Prefrontal Cortex on Behavioral Performance in a Go/NoGo Task. Brain Sci. 2021, 11, 483. https:// doi.org/10.3390/brainsci11040483 Academic Editors: Leonor J. Romero Lauro and Alex Green Received: 28 February 2021 Accepted: 9 April 2021 Published: 11 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 Department of Sensorimotor Neuroscience, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan; twatan@hiroshima-u.ac.jp (T.W.); e.orinoco26@gmail.com (N.K.); d185984@hiroshima-u.ac.jp (X.C.); d205546@hiroshima-u.ac.jp (K.Y.); d203652@hiroshima-u.ac.jp (T.M.); m203434@hiroshima-u.ac.jp (T.K.) 2 Japan Society for the Promotion of Science, Tokyo 102-0083, Japan 3 Department of Analysis and Control of Upper Extremity Function, Graduate School of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8553, Japan; torusuna@hiroshima-u.ac.jp (T.S.); sdate@hiroshima-u.ac.jp (S.D.) 4 Graduate School of Core Ethics and Frontier Sciences, Ritsumeikan University, Kyoto 603-8577, Japan; t-mima@fc.ritsumei.ac.jp * Correspondence: hkirimoto@hiroshima-u.ac.jp Abstract: The purpose of this pilot study was to investigate whether transcranial static magnetic field stimulation (tSMS), which can modulate cortical excitability, would influence inhibitory control function when applied over the dorsolateral prefrontal cortex (DLPFC). Young healthy adults (n = 8, mean age ± SD = 24.4 ± 4.1, six females) received the following stimulations for 30 min on different days: (1) tSMS over the left DLPFC, (2) tSMS over the right DLPFC, and (3) sham stimulation over either the left or right DLPFC. The participants performed a Go/NoGo task before, immediately after, and 10 min after the stimulation. They were instructed to extend the right wrist in response to target stimuli. We recorded the electromyogram from the right wrist extensor muscles and analyzed erroneous responses (false alarm and missed target detection) and reaction times. As a result, 50% of the participants made erroneous responses, and there were five erroneous responses in total (0.003%). A series of statistical analyses revealed that tSMS did not affect the reaction time. These preliminary findings suggest the possibility that tSMS over the DLPFC is incapable of modulating inhibitory control and/or that the cognitive load imposed in this study was insufficient to detect the effect. Keywords: transcranial static magnetic field stimulation; non-invasive brain stimulation; cognitive function; dorsolateral prefrontal cortex; response inhibition; Go/NoGo task 1. Introduction Transcranial static magnetic field stimulation (tSMS) is one of non-invasive brain stimulation (NIBS) tools that can modulate brain activity as well as motor and cognitive functions. Since Oliviero and colleagues reported a reduction of motor cortical excitability after application of tSMS over the motor cortex in 2011 [1], a relatively larger number of studies have been conducted to investigate the effectiveness of this new tool. For example, tSMS has been shown to reduce somatosensory-evoked potentials when applied over the sensorimotor cortex [2–4], and also to increase alpha-band power when applied over the parietal or occipital cortex [5,6]. Furthermore, recent studies revealed changes in cortical activity in brain regions apart from the site of stimulation [7–10]. With regard to behavioral parameters, tSMS has been demonstrated to impair performance of difficult reaction time task [5], postural adjustment task [11], and force-matching task [12] when it was applied over the occipital cortex, supplementary motor area, and motor cortex, respectively. Brain Sci. 2021, 11, 483. https://doi.org/10.3390/brainsci11040483 https://www.mdpi.com/journal/brainsci