Table I. Resting-state and structural studies of internet gaming disorder. *Studies arranged chronologically by publication year. †Regional Homogeneity (ReHo) is a voxel-based measure of brain activity that evaluates the similarity or synchronization between the time series of a given voxel and its nearest neighbors. This measure is based on the hypothesis that intrinsic brain activity is manifested by clusters of voxels rather than single voxels. ReHo can provide information about the local/regional activity of regions throughout the brain. ACC, anterior cingulate cortex (ACC); DLPFC, dorsolateral prefrontal cortex; IAT, internet addiction test; MRI, magnetic resonance imaging; OFC, orbitofrontal cortex; PCC, posterior cingulate cortex; RGU, recreational internet game use. Parts of Tables I and II reproduced with permission from ref 6: Weinstein A, Livny A, Weizman A. New devel­opments in brain research of internet and gaming disorder. Neurosci Biobehav Rev. 2017;75:314-330. Copyright © Elsevier 2017.

Citation*	Method	Participants	Main findings
Sun et al,11 2014	Gray-matter diffusion assessed via diffusional kurtosis imaging	18 IGD 21 control participants	Lower gray-matter diffusion in the right anterolateral cerebellum, right inferior and superior temporal gyri, right supplementary motor area, middle occipital gyrus, right precuneus, postcentral gyrus, right inferior frontal gyrus, left lateral lingual gyrus, left paracentral lobule, left ACC, median cingulate cortex, bilateral fusiform gyrus, insula, PCC, and thalamus. Higher gray-matter volume in the right inferior and middle temporal gyri, and right parahippocampal gyrus, and lower volume in the left precentral gyrus.
Wang et al,12 2015	Gray-matter volume measured via MRI	28 IGD 28 control participants	Smaller gray-matter volume of the bilateral ACC, precuneus, supplementary motor area, superior parietal lobule, left DLPFC, left insula, and bilateral cerebellum in IGD participants than in healthy control participants. Gray-matter volume of the ACC negatively correlated with the incongruent response errors on the Stroop test.
Kim et al,9 2015	Regional homogeneity (ReHo)† measured via MRI	16 IGD 14 alcohol-use disorder 15 control participants	IGD and alcohol-use disorder participants had increased ReHo in the PCC. IGD participants showed decreased ReHo in the right superior temporal gyrus compared with alcohol-use disorder and control partic-ipants. Patients with alcohol-use disorder showed decreased ReHo in the ACC.
Lin et al,13 2015	Gray-matter density and white-matter density changes assessed by voxel-based morphometric analysis in MRI.	35 IGD 36 control participants	Higher fractional anisotropy in the thalamus and left PCC. Higher fractional anisotropy in the thalamus was associated with greater severity of internet addiction.
Takeuchi et al,14 2016	Mean diffusivity assessed via diffusion tensor imaging	114 boys 126 girls	The amount of videogame play positively correlated with mean diffusivity in the left middle, inferior, and orbiofrontal cortxs (OFC); left pallidum; left putamen; left hippocampus; left caudate; right putamen; right insula; and thalamus in both cross-sectional and longitudinal analyses. Higher mean diffusivity in the areas of the left thalamus, left hippocampus, left putamen, left insula, and left Heschl gyrus was associated with lower intelligence.
Yuan et al,15 2016	Assessment of white-matter integrity and connectivity	28 IGD adolescents 25 control participants	Reduced fractional anisotropy in the ACC/right DLPFC pathways in IGD.
Zhai et al,16 2017	White-matter integrity measured via diffusion tensor imaging	16 right-handed adolescents with IGD 16 control participants	Reduced nodal efficiency in frontal cortex, ACC, and pallidum in IGD. Global efficiency of the white-matter network correlated with the IAT scores in IGD.
Jeong et al,17 2016	Assessment of white-matter integrity and connectivity	181 male patients including: 58 IGD subjects without psychiatric comorbidity 26 male control participants	Increased fractional anisotropy values within forceps minor, right anterior thalamic radiation; right corticospinal tract; right inferior longitudinal fasciculus; right cingulum to hippocampus; and right inferior fronto-occipital fasciculus (IFOF) decreases in radial diffusivity value within forceps minor, right anterior thalamic radiation andIFOF relative to control subjects
Sun et al,10 2019	Resting-state cerebral activity alterations assessed via amplitude of low-frequency fluctuation (ALFF) and functional connectivity	30 male IGD) 23 female IGD 30 male and 22 female age-matched healthy control participants	Greater ReHo* in the brain stem, inferior parietal lobule, cerebellum, and middle frontal gyrus. Lower ReHo in occipital and parietal areas.
Seok et al,18 2018	Assessment of resting-state gray-matter volume and functional connectivity	20 IGD 20 age- and sex-matched healthy control participants	IGD severity was positively correlated with gray-matter volume in the left caudate and it was negatively associated with functional connectivity between the left caudate and the right middle frontal gyrus.
Pan et al,19 2018	Assessment of resting-state gray-matter volume	67 male adolescents	IAT score was negatively correlated with gray-matter volumes of the bilateral postcentral gyri, the bilateral precentral gyri, the right precuneus, the left posterior midcingulate cortex, the left inferior parietal lobe, and the right middle frontal gyrus.
Lee et al,20 2018	Assessment of resting-state gray-matter volume	45 male adults with IGD 35 age-matched male control participants	IGD subjects had thinner cortices in the right rostral ACC, right lateral OFC, and left pars orbitalis than controls. Smaller gray-matter volume in the right caudal ACC and left pars orbital-is in IGD subjects. Thinner cortex of the right lateral OFC in IGD subjects correlated with higher cognitive impulsivity. Whole-brain analysis in IGD subjects revealed thinner cortices in the right supplementary motor area, left frontal eye field, superior parietal lobule, and posterior cingulate cortex.
Dong et al,21 2018	Assessment of white-matter integrity	42 IGD 44 RGU participants	Increased fractional anisotropy in the bilateral anterior thalamic radiation, anterior limb of the internal capsule, bilateral corticospinal tract, bilateral inferior fronto-occipital fasciculus, corpus callosum, and bilteral inferior longitudinal fasciculus. Internet-addiction severity was positively correlated with fractional anisotropy values.
Wang et al,22 2018	Assessment of cortical thickness and volume	38 IGD 66 RGU participants	IGD showed decreased cortical thickness in the left lateral OFC, inferior parietal lobule, bilateral cuneus, precentral gyrus, and right middle temporal gyrus. Reduced cortical volume in the left superior temporal gyrus and right supra marginal gyrus in IGD. Whole-brain correlational analysis indicated different correlations between the two groups.
Wang et al,22 2018	Assessment of cortical thickness and volume	48 IGD male youths 32 age- and education-matched control participants	IGD showed increased cortical thickness in the bilateral insulae and the right inferior temporal gyrus. Decreased cortical thickness in bilateral superior temporal sulci, the right inferior parietal cortex, the right precuneus, the right precentral gyrus, and the left middle temporal gyrus. A positive correlation between the left insular cortical thickness and symptom severity.