This study was supported by the National Research Foundation of Korea (NRF) funded by the Ministry of Science and ICT (2015M3C7A1064832, 2015M3C7A1028373, 2018M3A6A3058651) and by the National Institutes of Health (NIHNIMH 1R01MH111896, NIH-NINDS 1R01NS101362).

All experimental procedures presented in this protocol have been approved by the Institutional Review Board and are in accordance with the Declaration of Helsinki.
1. Research Participants
<ol>
	<li>Recruit individuals who report that they play online games (the gamer group) and those who report that they do not play online games (the non-gamer group). 
	NOTE: Here, we included individuals with two or more IGD symptoms according to the Diagnostic and Statistical Manual of Mental Disorders-523 or those who play games at least one hour per day on average in the gamer group. The non-gamer group undergoes only baseline brain FDG-PET scans to compare rCMRglu with the gamer group and does not receive tDCS sessions.</li>
	<li>For both groups, exclude individuals with (a) major medical, psychiatric, or neurological disorders, (b) history of traumatic brain injury, (c) history of alcohol or other substance abuse or dependence, (d) use of psychotropic medications, or (e) any contraindications for tDCS such as severe headache, metal in the head, history of seizure, epilepsy, or brain surgery, or any lesions or other medical problems on the skin where tDCS electrodes will be attached.</li>
	<li>Explain to each participant the aim of the study, the main experimental procedures, and any potential risks associated with participating in the study. After answering any questions, obtain written consent.</li>
</ol>
2. Baseline Assessment
<ol>
	<li>Evaluate clinical characteristics using the following questionnaires: Internet Addiction Test (IAT)24 and Brief Self Control Scale (BSCS)25. In addition, ask participants to report average weekly hours spent playing games. 
	NOTE: The word &#34;Internet&#34; in the IAT is replaced with &#34;online games&#34; to assess severity of online game addiction.</li>
	<li>Perform brain FDG-PET scans.
	<ol>
		<li>Inject participants with 185 - 222 MBq of FDG and have participants rest for 45 min of an uptake period during which they are awake and resting in supine position in a dark and quiet room with their eyes closed.</li>
		<li>Conduct brain FDG-PET scans to acquire transaxial emission images and CT images using a PET-CT scanner in about 15 min. Apply attenuation correction, standard filtering, and standard reconstruction techniques.</li>
	</ol>
	</li>
</ol>
3. Application of tDCS
<ol>
	<li>Within a week after the baseline assessment, apply tDCS to participants. Prepare tDCS sessions with following materials: a tDCS device, wet wipes, saline solution, two sponge electrodes (6 cm in diameter), a cable, a headcap, and a headband.</li>
	<li>Have the participant sit on a chair.</li>
	<li>Set the stimulation parameters for the tDCS device: 2 mA for 30 min (current density = 0.07 mA/cm2). Set the current so it ramps up to 2.0 mA over 30 s, remains at 2.0 mA for 29 min, and ramps down to 0 mA over the last 30 s.</li>
	<li>Put the headcap (the International 10-20 system) on the participant&#8217;s head and mark the left dorsolateral prefrontal cortex (F3) and the right dorsolateral prefrontal cortex (F4). Then, remove the headcap from the participant&#39;s head.</li>
	<li>Place two sponge electrodes in the rubber holders of the headband and soak them with saline solution.</li>
	<li>Remove any makeup, dirt, or sweat on the scalp where the electrodes will be applied.</li>
	<li>Place the headband over the marking points by putting the anodal electrode over the left DLPFC and the cathodal electrode over the right DLPFC.</li>
	<li>Connect the electrodes to the tDCS device using the cable and turn on the device.</li>
	<li>Ask the participant to report any adverse effects during or after the tDCS session.</li>
	<li>At the end of the 30 min of stimulation, turn off the device and remove the electrodes from the participant.</li>
	<li>Administer a total of 12 tDCS sessions (3 times per week for 4 weeks).</li>
</ol>
4. Follow-up Assessment
<ol>
	<li>Perform the follow-up assessment within a week after the last tDCS session using the same protocol as the baseline assessment.</li>
</ol>
5. Data Analysis
<ol>
	<li>Use an appropriate software package to preprocess the PET images (e.g., Statistical Parametric Mapping 12).
	<ol>
		<li>Convert DICOM files to NIFTI files.</li>
		<li>Spatially normalize all PET images to the standard PET template.</li>
	</ol>
	</li>
	<li>Create binary masks for the left and right DLPFC (e.g., WFU PickAtlas toolbox). The DLPFC is defined by the middle frontal gyrus in the Automated Anatomical Labeling atlas.</li>
	<li>Extract rCMRglu of the left and right DLPFC using the masks (e.g., MarsBaR toolbox). The rCMRglu is normalized to global mean uptake using proportional scaling.</li>
	<li>Calculate asymmetry index (AI) of rCMRglu in the DLPFC as (rCMRglu right - rCMRglu left) / [(rCMRglu right + rCMRglu left) / 2] &#215; 100. Positive AI indicates right-greater-than-left asymmetry of glucose metabolism.</li>
</ol>

<ol>
	<li>Chen, Y. F., Peng, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=University+students'+Internet+use+and+its+relationships+with+academic+performance,+interpersonal+relationships,+psychosocial+adjustment,+and+self-evaluation.">University students' Internet use and its relationships with academic performance, interpersonal relationships, psychosocial adjustment, and self-evaluation.</a> CyberPsychology &amp; Behavior. 11 (4), 467-469 (2008).</li><li>Ho, R. C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+association+between+internet+addiction+and+psychiatric+co-morbidity:+a+meta-analysis.">The association between internet addiction and psychiatric co-morbidity: a meta-analysis.</a> BMC Psychiatry. 14, 183 (2014).</li><li>Pawlikowski, M., Brand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excessive+Internet+gaming+and+decision+making:+do+excessive+World+of+Warcraft+players+have+problems+in+decision+making+under+risky+conditions.">Excessive Internet gaming and decision making: do excessive World of Warcraft players have problems in decision making under risky conditions.</a> Psychiatry Research. 188 (3), 428-433 (2011).</li><li>Zajac, K., Ginley, M. K., Chang, R., Petry, N. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatments+for+Internet+gaming+disorder+and+Internet+addiction:+A+systematic+review.">Treatments for Internet gaming disorder and Internet addiction: A systematic review.</a> Psychology of Addictive Behaviors. 31 (8), 979-994 (2017).</li><li>Weinstein, A. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=An+Update+Overview+on+Brain+Imaging+Studies+of+Internet+Gaming+Disorder.">An Update Overview on Brain Imaging Studies of Internet Gaming Disorder.</a> Frontiers in Psychiatry. 8, 185 (2017).</li><li>Park, B., Han, D. H., Roh, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neurobiological+findings+related+to+Internet+use+disorders.">Neurobiological findings related to Internet use disorders.</a> Psychiatry and Clinical Neurosciences. 71 (7), 467-478 (2017).</li><li>Kober, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prefrontal-striatal+pathway+underlies+cognitive+regulation+of+craving.">Prefrontal-striatal pathway underlies cognitive regulation of craving.</a> Proceedings of the National Academy of Sciences of the United States of America. 107 (33), 14811-14816 (2010).</li><li>Li, C. S., Luo, X., Yan, P., Bergquist, K., Sinha, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Altered+impulse+control+in+alcohol+dependence:+neural+measures+of+stop+signal+performance.">Altered impulse control in alcohol dependence: neural measures of stop signal performance.</a> Alcoholism: Clinical and Experimental Research. 33 (4), 740-750 (2009).</li><li>Fecteau, S., Fregni, F., Boggio, P. S., Camprodon, J. A., Pascual-Leone, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuromodulation+of+decision-making+in+the+addictive+brain.">Neuromodulation of decision-making in the addictive brain.</a> Substance Use &amp; Misuse. 45 (11), 1766-1786 (2010).</li><li>Fujimoto, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deficit+of+state-dependent+risk+attitude+modulation+in+gambling+disorder.">Deficit of state-dependent risk attitude modulation in gambling disorder.</a> Translational Psychiatry. 7 (4), 1085 (2017).</li><li>Choi, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Structural+alterations+in+the+prefrontal+cortex+mediate+the+relationship+between+Internet+gaming+disorder+and+depressed+mood.">Structural alterations in the prefrontal cortex mediate the relationship between Internet gaming disorder and depressed mood.</a> Scientific Reports. 7 (1), 1245 (2017).</li><li>Yuan, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microstructure+abnormalities+in+adolescents+with+internet+addiction+disorder.">Microstructure abnormalities in adolescents with internet addiction disorder.</a> PLoS One. 6 (6), 20708 (2011).</li><li>Ko, C. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Brain+activities+associated+with+gaming+urge+of+online+gaming+addiction.">Brain activities associated with gaming urge of online gaming addiction.</a> Journal of Psychiatric Research. 43 (7), 739-747 (2009).</li><li>Gordon, H. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Laterality+of+Brain+Activation+for+Risk+Factors+of+Addiction.">Laterality of Brain Activation for Risk Factors of Addiction.</a> Current Drug Abuse Reviews. 9 (1), 1-18 (2016).</li><li>Tian, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PET+imaging+reveals+brain+functional+changes+in+internet+gaming+disorder.">PET imaging reveals brain functional changes in internet gaming disorder.</a> European Journal of Nuclear Medicine and Molecular Imaging. 41 (7), 1388-1397 (2014).</li><li>Nitsche, M. A., Paulus, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Excitability+changes+induced+in+the+human+motor+cortex+by+weak+transcranial+direct+current+stimulation.">Excitability changes induced in the human motor cortex by weak transcranial direct current stimulation.</a> Journal of Physiology. 527, 633-639 (2000).</li><li>Bikson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+of+Transcranial+Direct+Current+Stimulation:+Evidence+Based+Update+2016.">Safety of Transcranial Direct Current Stimulation: Evidence Based Update 2016.</a> Brain Stimulation. 9 (5), 641-661 (2016).</li><li>Boggio, P. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Prefrontal+cortex+modulation+using+transcranial+DC+stimulation+reduces+alcohol+craving:+a+double-blind,+sham-controlled+study.">Prefrontal cortex modulation using transcranial DC stimulation reduces alcohol craving: a double-blind, sham-controlled study.</a> Drug and Alcohol Dependence. 92 (1-3), 55-60 (2008).</li><li>Martinotti, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gambling+disorder+and+bilateral+transcranial+direct+current+stimulation:+A+case+report.">Gambling disorder and bilateral transcranial direct current stimulation: A case report.</a> Journal of Behavioral Addictions. 7 (3), 834-837 (2018).</li><li>Martinotti, G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+Direct+Current+Stimulation+Reduces+Craving+in+Substance+Use+Disorders:+A+Double-blind,+Placebo-Controlled+Study.">Transcranial Direct Current Stimulation Reduces Craving in Substance Use Disorders: A Double-blind, Placebo-Controlled Study.</a> Journal of ECT. , (2019).</li><li>Gay, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+single+session+of+repetitive+transcranial+magnetic+stimulation+of+the+prefrontal+cortex+reduces+cue-induced+craving+in+patients+with+gambling+disorder.">A single session of repetitive transcranial magnetic stimulation of the prefrontal cortex reduces cue-induced craving in patients with gambling disorder.</a> European Psychiatry. 41, 68-74 (2017).</li><li>Pettorruso, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dopaminergic+and+clinical+correlates+of+high-frequency+repetitive+transcranial+magnetic+stimulation+in+gambling+addiction:+a+SPECT+case+study.">Dopaminergic and clinical correlates of high-frequency repetitive transcranial magnetic stimulation in gambling addiction: a SPECT case study.</a> Addictive Behaviors. 93, 246-249 (2019).</li><li>American Psychiatric Association. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnostic+and+Statistical+Manual+of+Mental+Disorders,+5th+edn.">Diagnostic and Statistical Manual of Mental Disorders, 5th edn.</a> American Psychiatric Association. , (2013).</li><li>Young, K. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Internet+addiction:+the+emergence+of+a+new+clinical+disorder.">Internet addiction: the emergence of a new clinical disorder.</a> CyberPsychology &amp; Behavior. 1 (3), 237-244 (1998).</li><li>Tangney, J. P., Baumeister, R. F., Boone, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High+self-control+predicts+good+adjustment,+less+pathology,+better+grades,+and+interpersonal+success.">High self-control predicts good adjustment, less pathology, better grades, and interpersonal success.</a> Journal of Personality. 72 (2), 271-324 (2004).</li><li>Bentourkia, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+regional+cerebral+blood+flow+and+glucose+metabolism+in+the+normal+brain:+effect+of+aging.">Comparison of regional cerebral blood flow and glucose metabolism in the normal brain: effect of aging.</a> Journal of the Neurological Sciences. 181 (1-2), 19-28 (2000).</li><li>Lee, S. H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+direct+current+stimulation+for+online+gamers:+A+prospective+single-arm+feasibility+study.">Transcranial direct current stimulation for online gamers: A prospective single-arm feasibility study.</a> Journal of Behavioral Addictions. 7 (4), 1166-1170 (2018).</li><li>Bikson, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Response+to+letter+to+the+editor:+Safety+of+transcranial+direct+current+stimulation:+Evidence+based+update+2016.">Response to letter to the editor: Safety of transcranial direct current stimulation: Evidence based update 2016.</a> Brain Stimulation. 10 (5), 986-987 (2017).</li><li>Chhatbar, P. Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+and+tolerability+of+transcranial+direct+current+stimulation+to+stroke+patients+-+A+phase+I+current+escalation+study.">Safety and tolerability of transcranial direct current stimulation to stroke patients - A phase I current escalation study.</a> Brain Stimulation. 10 (3), 553-559 (2017).</li><li>Thair, H., Holloway, A. L., Newport, R., Smith, A. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+Direct+Current+Stimulation+(tDCS):+A+Beginner's+Guide+for+Design+and+Implementation.">Transcranial Direct Current Stimulation (tDCS): A Beginner's Guide for Design and Implementation.</a> Frontiers in Neuroscience. 11, 641 (2017).</li><li>Wagner, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+direct+current+stimulation:+a+computer-based+human+model+study.">Transcranial direct current stimulation: a computer-based human model study.</a> Neuroimage. 35 (3), 1113-1124 (2007).</li><li>Lefaucheur, J. P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Evidence-based+guidelines+on+the+therapeutic+use+of+transcranial+direct+current+stimulation+(tDCS).">Evidence-based guidelines on the therapeutic use of transcranial direct current stimulation (tDCS).</a> Clinical Neurophysiology. 128 (1), 56-92 (2017).</li><li>Carvalho, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Home-Based+Transcranial+Direct+Current+Stimulation+Device+Development:+An+Updated+Protocol+Used+at+Home+in+Healthy+Subjects+and+Fibromyalgia+Patients.">Home-Based Transcranial Direct Current Stimulation Device Development: An Updated Protocol Used at Home in Healthy Subjects and Fibromyalgia Patients.</a> Journal of Visualized Experiments. (137), (2018).</li><li>Shaw, M. T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Remotely+Supervised+Transcranial+Direct+Current+Stimulation:+An+Update+on+Safety+and+Tolerability.">Remotely Supervised Transcranial Direct Current Stimulation: An Update on Safety and Tolerability.</a> Journal of Visualized Experiments. (128), (2017).</li><li>Bikson, M., Rahman, A., Datta, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Computational+models+of+transcranial+direct+current+stimulation.">Computational models of transcranial direct current stimulation.</a> Clinical EEG and Neuroscience. 43 (3), 176-183 (2012).</li><li>Gandiga, P. C., Hummel, F. C., Cohen, L. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+DC+stimulation+(tDCS):+a+tool+for+double-blind+sham-controlled+clinical+studies+in+brain+stimulation.">Transcranial DC stimulation (tDCS): a tool for double-blind sham-controlled clinical studies in brain stimulation.</a> Clinical Neurophysiology. 117 (4), 845-850 (2006).</li><li>Cho, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+of+the+Internet+addiction+scale+based+on+the+Internet+Gaming+Disorder+criteria+suggested+in+DSM-5.">Development of the Internet addiction scale based on the Internet Gaming Disorder criteria suggested in DSM-5.</a> Addictive Behaviors. 39 (9), 1361-1366 (2014).</li><li>Han, D. H., Hwang, J. W., Renshaw, P. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Bupropion+sustained+release+treatment+decreases+craving+for+video+games+and+cue-induced+brain+activity+in+patients+with+Internet+video+game+addiction.">Bupropion sustained release treatment decreases craving for video games and cue-induced brain activity in patients with Internet video game addiction.</a> Experimental and Clinical Psychopharmacology. 18 (4), 297-304 (2010).</li></ol>

The City University of New York (CUNY) has IP on neurostimulation system and methods with Marom Bikson as inventor. Marom Bikson has equity in Soterix Medical Inc and serves as a consultant for Boston Scientific Inc. All other authors declare no financial conflicts of interest.

We have presented a tDCS and neuroimaging protocol for online gamers and assessed its feasibility. The results demonstrated that repeated sessions of tDCS over the DLPFC reduced online game addiction symptoms and average time spent on games and increased self-control. An increase in self-control was correlated with a decrease in addiction symptoms. Moreover, the abnormal asymmetry of rCMRglu in the DLPFC where the right side was greater than the left side was improved after the tDCS sessions in the gamer group. These res...

In recent years, increasing attention has been paid to excessive online game use since its associations with negative impact on mental health and daily functioning as well as with internet gaming disorder (IGD) have been reported1,2,3. Although several treatment strategies including pharmacotherapy and cognitive-behavioral therapy have been evaluated, evidence for their effectiveness is limited4.
Previous studies have suggested that IGD may share clinical and neurobiological similarities with other behavioral addictions and substance use disorders5,6. It has been reported that the dorsolateral prefrontal cortex (DLPFC) is closely involved in the pathophysiology of substance and behavioral addiction such as craving7, impulse control8, decision making9, and cognitive flexibility10. Several neuroimaging studies on IGD have reported structural and functional impairments in the DLPFC6. In particular, structural neuroimaging studies revealed a reduction in gray matter density in the DLPFC11,12 and a functional magnetic resonance imaging (fMRI) study found an altered cued-induced activity in the DLPFC of patients with IGD13. In addition, functional asymmetry of the brain may contribute to impulsivity and craving in addictions including IGD. For instance, cue-induced craving for online gaming could be related to right prefrontal activations14. However, alterations of regional cerebral metabolic rate of glucose (rCMRglu) associated with excessive online game use or IGD remain to be further investigated compared to other brain deficits15.
Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that applies a weak electric current (1-2 mA) through electrodes attached to the scalp to modulate neuronal membrane potentials. Generally, the cortical excitability is increased under the anode electrode and decreased under the cathode electrode16. tDCS has become a popular method because it is simple, inexpensive, and safe to administer compared to other brain stimulation techniques such as transcranial magnetic stimulation (TMS) that uses a magnetic pulse to generate an electrical current in the brain tissue under the coil. According to a recent review, the use of conventional tDCS protocols has not produced any serious adverse effects or irreversible injury and is associated with only mild and transient itching or tingling sensation under the stimulation area17.
Several studies have demonstrated favorable results of tDCS18,19,20 and repetitive TMS21,22 over the DLPFC for treating behavioral and substance addiction. However, further studies are needed to investigate the effects of brain stimulation techniques on online game use and the underlying brain changes.
The aim of this study is to present a protocol for applying repeated sessions of tDCS over the DLPFC and neuroimaging to examine the underlying neural correlates in gamers using 18F-&#64258;uoro-2-deoxyglucose positron emission tomography (FDG-PET), as well as to assess its feasibility. Specifically, we focused on changes in addiction symptoms, average time spent on games, self-control, and asymmetry of rCMRglu in the DLPFC.

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	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Discovery STE PET/CT Imaging System</td>
			<td style="width:389px;">GE Healthcare</td>
			<td style="width:161px;"></td>
			<td style="width:576px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">MarsBaR region of interest toolbox for SPM</td>
			<td style="width:389px;">Matthew Brett</td>
			<td style="width:161px;"></td>
			<td>Neuroimaging analysis software; http://marsbar.sourceforge.net/</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">Statistical Parametric Mapping 12</td>
			<td>Wellcome Centre for Human Neuroimaging</td>
			<td style="width:161px;"></td>
			<td>Neuroimaging analysis software; https://www.fil.ion.ucl.ac.uk/spm/software/spm12/</td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:299px;">Transcranial direct current stimulation device</td>
			<td style="width:389px;">Ybrain</td>
			<td style="width:161px;">YDS-301N</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:299px;">WFU_PickAtlas</td>
			<td colspan="2">ANSIR Laboratory, Wake Forest University School of Medicine</td>
			<td>Neuroimaging analysis software; https://www.nitrc.org/projects/wfu_pickatlas/</td>
		</tr>
	</tbody>
</table>

transcranial direct current stimulation for online gamers

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that applies a weak electric current to the scalp to modulate neuronal membrane potentials. Compared to other brain stimulation methods, tDCS is relatively safe, simple, and inexpensive to administer.
Since excessive online gaming can negatively affect mental health and daily functioning, developing treatment options for gamers is necessary. Although tDCS over the dorsolateral prefrontal cortex (DLPFC) has demonstrated promising results for various addictions, it has not been tested in gamers. This paper describes a protocol and a feasibility study for applying repeated tDCS over the DLPFC and neuroimaging to examine the underlying neural correlates in gamers.
At baseline, individuals who play online games report average weekly hours spent on games, complete questionnaires on addiction symptoms and self-control, and undergo brain 18F-&#64258;uoro-2-deoxyglucose positron emission tomography (FDG-PET). The tDCS protocol consists of 12 sessions over the DLPFC for 4 weeks (anode F3/cathode F4, 2 mA for 30 min per session). Then, a follow-up is conducted using the same protocol as the baseline. Individuals who do not play online games receive only baseline FDG-PET scans without tDCS. Changes of clinical characteristics and asymmetry of regional cerebral metabolic rate of glucose (rCMRglu) in the DLPFC are examined in gamers. In addition, asymmetry of rCMRglu is compared between gamers and non-gamers at baseline.
In our experiment, 15 gamers received tDCS sessions and completed baseline and follow-up scans. Ten non-gamers underwent FDG-PET scans at the baseline. The tDCS reduced addiction symptoms, time spent on games, and increased self-control. Moreover, abnormal asymmetry of rCMRglu in the DLPFC at baseline was alleviated after tDCS.
The current protocol may be useful for assessing treatment efficacy of tDCS and its underlying brain changes in gamers. Further randomized sham-controlled studies are warranted. Moreover, the protocol can be applied to other neurological and psychiatric disorders.

A total of 15 gamers (Table 1) and 10 non-gamers were recruited. The mean age of the gamer group (21.3 &#177; 1.4) was significantly lower than that of the non-gamer group (28.8 &#177; 7.5) (t = -3.81, p &#60; 0.001). There were 8 men in the gamer group and 6 men in the non-gamer group (&#967;2 = 0.11, p = 0.74).
Behavioral results using linear mixed models indicate that the tDCS sessions successfully lowered the IAT score (z = -4.29, p &#60; 0.001), weekly hours sp...

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Transcranial Direct Current Stimulation for Online Gamers

We present a protocol and a feasibility study for applying transcranial direct current stimulation (tDCS) and neuroimaging assessment in online gamers.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that applies a weak electric current to the scalp to modulate ...

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7.9K Views.  The Catholic University of Korea. We present a protocol and a feasibility study for applying transcranial direct current stimulation (tDCS) and neuroimaging assessment in online gamers.

Video: Transcranial Direct Current Stimulation for Online Gamers

Simultaneous EEG Monitoring During Transcranial Direct Current Stimulation

Transcranial direct current stimulation (tDCS) is a technique that delivers weak electric currents through the scalp. This constant electric current induces shifts in neuronal membrane excitability, resulting in secondary changes in cortical activity. Although tDCS has most of its neuromodulatory effects on the underlying cortex, tDCS effects can also be observed in distant neural networks. Therefore, concomitant EEG monitoring of the effects of tDCS can provide valuable information on the mechanisms of tDCS. In addition, EEG findings can be an important surrogate marker for the effects of tDCS and thus can be used to optimize its parameters. This combined EEG-tDCS system can also be used for preventive treatment of neurological conditions characterized by abnormal peaks of cortical excitability, such as seizures. Such a system would be the basis of a non-invasive closed-loop device. In this article, we present a novel device that is capable of utilizing tDCS and EEG simultaneously. For that, we describe in a step-by-step fashion the main procedures of the application of this device using schematic figures, tables and video demonstrations. Additionally, we provide a literature review on clinical uses of tDCS and its cortical effects measured by EEG techniques.

Transcranial direct current stimulation (tDCS) is a non-invasive brain stimulation technique that has shown initial therapeutic effects in several neurological conditions. The main mechanism underlying these therapeutic effects is the modulation of cortical excitability. Therefore, online monitoring of cortical excitability would help guide stimulation parameters and optimize its therapeutic effects. In the present article we review the use of a novel device that combines simultaneous tDCS and EEG monitoring in real time.

Transcranial  direct current stimulation (tDCS) is a technique that delivers weak electric  currents through the scalp. This constant electric current ...

Stimulating the Lip Motor Cortex with Transcranial Magnetic Stimulation

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. Researchers have used single-pulse and repetitive TMS to stimulate the lip representation in the motor cortex. The excitability of the lip motor representation can be investigated by applying single TMS pulses over this cortical area and recording TMS-induced motor evoked potentials (MEPs) via electrodes attached to the lip muscles (electromyography; EMG). Larger MEPs reflect increased cortical excitability. Studies have shown that excitability increases during listening to speech as well as during&#160;viewing speech-related movements. TMS can be used also to disrupt the lip motor representation. A 15-min train of low-frequency sub-threshold repetitive stimulation has been shown to suppress motor excitability for a further 15-20 min. This TMS-induced disruption of the motor lip representation impairs subsequent performance in demanding speech perception tasks and modulates auditory-cortex responses to speech sounds. These findings are consistent with the suggestion that the motor cortex contributes to speech perception. This article describes how to localize the lip representation in the motor cortex and how to define the appropriate stimulation intensity for carrying out both single-pulse and repetitive TMS experiments.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception.&#160; This article describes how to record motor evoked potentials (MEPs) from the lip muscles and how to disrupt the motor lip representation using repetitive TMS.

Transcranial magnetic stimulation (TMS) has proven to be a useful tool in investigating the role of the articulatory motor cortex in speech perception. ...

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG).
In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site&#160;and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity.
Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique. It has successfully been used in basic research and clinical settings to modulate brain function in humans. This article describes the implementation of tDCS and simultaneous functional magnetic resonance imaging (fMRI), to investigate the neural basis of tDCS effects.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily disrupt information processing in a brain region, generating a short-lived &#8220;virtual lesion.&#8221; Stimulation that interferes with task performance indicates that the affected brain region is necessary to perform the task normally. In other words, unlike neuroimaging methods such as functional magnetic resonance imaging (fMRI) that indicate correlations between brain and behavior, TMS can be used to demonstrate causal brain-behavior relations. Furthermore, by varying the duration and onset of the virtual lesion, TMS can also reveal the time course of normal processing. As a result, TMS has become an important tool in cognitive neuroscience. Advantages of the technique over lesion-deficit studies include better spatial-temporal precision of the disruption effect, the ability to use participants as their own control subjects, and the accessibility of participants. Limitations include concurrent auditory and somatosensory stimulation that may influence task performance, limited access to structures more than a few centimeters from the surface of the scalp, and the relatively large space of free parameters that need to be optimized in order for the experiment to work. Experimental designs that give careful consideration to appropriate control conditions help to address these concerns. This article illustrates these issues with TMS results that investigate the spatial and temporal contributions of the left supramarginal gyrus (SMG) to reading.

Transcranial magnetic stimulation (TMS) is a technique for non-invasively disrupting neural information processing and measuring its effect on behavior. When TMS interferes with a task, it indicates that the stimulated brain region is necessary for normal task performance, allowing one to systematically relate brain regions to cognitive functions.

Transcranial magnetic stimulation (TMS) is a safe, non-invasive brain stimulation technique that uses a strong electromagnet in order to temporarily ...

Modulating Cognition Using Transcranial Direct Current Stimulation of the Cerebellum

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain regions involved in working memory and attention using transcranial electrical brain stimulation. Some researchers now believe the cerebellum supports cognition, possibly via a remote neuromodulatory effect on the prefrontal cortex. This paper describes a procedure for investigating a role for the cerebellum in cognition using transcranial direct current stimulation (tDCS), and a selection of information-processing tasks of varying task difficulty, which have previously been shown to involve working memory, attention and cerebellar functioning. One task is called the Paced Auditory Serial Addition Task (PASAT) and the other a novel variant of this task called the Paced Auditory Serial Subtraction Task (PASST). A verb generation task and its two controls (noun and verb reading) were also investigated. All five tasks were performed by three separate groups of participants, before and after the modulation of cortico-cerebellar connectivity using anodal, cathodal or sham tDCS over the right cerebellar cortex. The procedure demonstrates how performance (accuracy, verbal response latency and variability) could be selectively improved after cathodal stimulation, but only during tasks that the participants rated as difficult, and not easy. Performance was unchanged by anodal or sham stimulation. These findings demonstrate a role for the cerebellum in cognition, whereby activity in the left prefrontal cortex is likely dis-inhibited by cathodal tDCS over the right cerebellar cortex. Transcranial brain stimulation is growing in popularity in various labs and clinics. However, the after-effects of tDCS are inconsistent between individuals and not always polarity-specific, and may even be task- or load-specific, all of which requires further study. Future efforts might also be guided towards neuro-enhancement in cerebellar patients presenting with cognitive impairment once a better understanding of brain stimulation mechanisms has emerged.

Transcranial direct current stimulation (tDCS) over the cerebellum exerts a remote effect on the prefrontal cortex, which can modulate cognition and performance. This was demonstrated using two information-processing tasks of varying complexity, whereby only cathodal tDCS improved performance when the task was difficult, but not easy.

Numerous studies have emerged recently that demonstrate the possibility of modulating, and in some cases enhancing, cognitive processes by exciting brain ...

Methods to Test Visual Attention Online

Online data collection methods have particular appeal to behavioral scientists because they offer the promise of much larger and much more representative data samples than can typically be collected on college campuses. However, before such methods can be widely adopted, a number of technological challenges must be overcome &#8211; in particular in experiments where tight control over stimulus properties is necessary. Here we present methods for collecting performance data on two tests of visual attention. Both tests require control over the visual angle of the stimuli (which in turn requires knowledge of the viewing distance, monitor size, screen resolution, etc.) and the timing of the stimuli (as the tests involve either briefly flashed stimuli or stimuli that move at specific rates). Data collected on these tests from over 1,700 online participants were consistent with data collected in laboratory-based versions of the exact same tests. These results suggest that with proper care, timing/stimulus size dependent tasks can be deployed in web-based settings.

To replicate laboratory settings, online data collection methods for visual tasks require tight control over stimulus presentation. We outline methods for the use of a web application to collect performance data on two tests of visual attention.

Online data collection methods have particular appeal to behavioral scientists because they offer the promise of much larger and much more representative ...

Multifunctional Setup for Studying Human Motor Control Using Transcranial Magnetic Stimulation, Electromyography, Motion Capture, and Virtual Reality

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular function include transcranial magnetic stimulation, electromyography, and three-dimensional motion capture. The advent of readily available and cost-effective virtual reality solutions has expanded the capabilities of researchers in recreating &#8220;real-world&#8221; environments and movements in a laboratory setting. Naturalistic movement analysis will not only garner a greater understanding of motor control in healthy individuals, but also permit the design of experiments and rehabilitation strategies that target specific motor impairments (e.g. stroke). The combined use of these tools will lead to increasingly deeper understanding of neural mechanisms of motor control. A key requirement when combining these data acquisition systems is fine temporal correspondence between the various data streams. This protocol describes a multifunctional system&#8217;s overall connectivity, intersystem signaling, and the temporal synchronization of recorded data. Synchronization of the component systems is primarily accomplished through the use of a customizable circuit, readily made with off the shelf components and minimal electronics assembly skills.

Transcranial magnetic stimulation, electromyography, and 3D motion capture are commonly used non-invasive techniques for investigating neuromuscular function in humans. In this paper, we describe a protocol that synchronously samples data generated by all three of these tools along with the unique addition of virtual reality stimulus presentation and feedback.

The study of neuromuscular control of movement in humans is accomplished with numerous technologies. Non-invasive methods for investigating neuromuscular ...

Neuronavigation-guided Repetitive Transcranial Magnetic Stimulation for Aphasia

Repetitive transcranial magnetic stimulation (rTMS) is widely used for several neurological conditions, as it has gained acknowledgement for its potential therapeutic effects. Brain excitability is non-invasively modulated by rTMS, and rTMS to the language areas has proved its potential effects on treatment of aphasia. In our protocol, we aim to artificially induce virtual aphasia in healthy subjects by inhibiting Brodmann area 44 and 45 using neuronavigational TMS (nTMS), and F3 of the International 10-20 EEG system for conventional TMS (cTMS). To measure the degree of aphasia, changes in reaction time to a picture naming task pre- and post-stimulation are measured and compare the delay in reaction time between nTMS and cTMS. Accuracy of the two TMS stimulation methods is compared by averaging the Talairach coordinates of the target and the actual stimulation. Consistency of stimulation is demonstrated by the error range from the target. The purpose of this study is to demonstrate use of nTMS and to describe the benefits and limitations of the nTMS compared to those of cTMS.

This study is designed to test the hypothesis that neuronavigational system-guided transcranial magnetic stimulation has higher accuracy for targeting the intended target as demonstrated by eliciting a greater degree of virtual aphasia in healthy subjects, measured by delay in reaction time to picture naming.

Repetitive transcranial magnetic stimulation (rTMS) is widely used for several neurological conditions, as it has gained acknowledgement for its potential ...

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized.

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation tACS

In this article we explain how to set up a concurrent transcranial alternating current stimulation and EEG experiment.

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to ...

Treating Clinical Depression with Repetitive Deep Transcranial Magnetic Stimulation Using the Brainsway H1-coil

Repetitive transcranial magnetic stimulation (rTMS) is an emerging non-pharmacological approach to treating many brain-based disorders. rTMS uses electromagnetic coils to stimulate areas of the brain non-invasively. Deep transcranial magnetic stimulation (dTMS) with the Brainsway H1-coil system specifically is a type of rTMS indicated for treating patients with major depressive disorder (MDD) who are resistant to medication. The unique H1-coil design of this device is able to stimulate neuronal pathways that lie deeper in the targeted brain areas than those reached by conventional rTMS coils. dTMS is considered to be low-risk and well tolerated, making it a viable treatment option for people who have not responded to medication or psychotherapy trials for their depression.
Randomized, sham-control studies have demonstrated that dTMS produces significantly greater improvement in depressive symptoms than sham dTMS treatment in patients with major depression that has not responded to antidepressant medication. In this paper, we will review the methodology for treating major depression with dTMS using an H1-coil.

Here we present a protocol outlining the methodology for treatment of Major Depressive Disorder using the deep Transcranial Magnetic Stimulation (dTMS) system.