Table 3 Characteristics of resting state brain imaging data in individuals with IGD

Han et al. (2017) [54]

IGD group: N = 78 (boys), 14.7 ± 2.0 years.

Control group: N = 73 (boys), 14.6 ± 1.8 years.

1) Excessive online game play time (more than 4 h per day/30 h per week); 2) IAT scores > 50; 3) Irritable, anxious and aggressive behavior when forced to stop online game play; 4) Impaired behaviors or distress, economic crisis and maladaptive regular life patterns including disrupted diurnal rhythms, irregular meals, failure to maintain personal hygiene and school refusal.

Method: fMRI (functional connectivity)

Scanner: 3 T

Software: AFNI, SPM12b, MatLab

IGD group showed increased functional connectivity between seven pairs of regions; left frontal eye field to dorsal anterior cingulate, left frontal eye field to right anterior insula, left DLPFC to left TPJ, right DLPFC to right TPJ, right auditory cortex to right motor cortex, right auditory cortex to supplementary motor area, and right auditory cortex to dorsal anterior cingulate.

Park et al. (2017) [38]

IGA group: N = 19 (boys) 13.6 ± 1.0 years.

Control group: N = 20 (boys), 13.4 ± 0.9 years.

Korean Internet Addiction Proneness Scale

Method: fMRI

Scanner: 3 T

Software: SPM8 and Data Processing Assistant for Resting-State Functional (DPARSF)

1) Brain functional networks in IGA group showed higher global efficiency and lower local efficiency relative to the controls; IGA induced brain functional networks to shift toward a random topological architecture.

2) IGA group exhibited consistently higher regional global efficiency over the frontal-sensorimotor, frontal-temporal, frontal-limbic, and temporal region, and lower regional local efficiency in the sensorimotor and limbic regions than those of the controls.

3) Severe impulsiveness in IGA group was associated with topological alterations over frontolimbic connections.

Jin et al. (2016) [52]

IGD group: N = 25 (16 boys and 9 girls), 19.1 ± 1.1 years.

Control group: N = 21 (14 boys and 7 girls), 18.8 ± 1.8 years.

DSM-5

Method: VBM and fMRI (functional connectivity)

Scanner: 3 T

Software: FMRIB Software Library (FSL) 4.1

IGD group showed:

1) Decreased gray matter volume in PFC regions including the bilateral DLPFC, OFC, ACC, and the right SMA.

2) Decreased functional connectivity between several cortical regions and authors’ seeds, including the insula, and temporal and occipital cortices.

3) Decreased functional connectivity between some subcortical regions, i.e., dorsal striatum, pallidum, and thalamus.

Du et al. (2016) [35]

IGD group: N = 25 (boys), 17.3 ± 3.4 years.

Control group: N = 27 (boys), 17.5 ± 2.9 years.

[1] five or more “yes” responses on the YDQ for internet addition; [2] online game playing time ≥ 4 h per day; and [3] IAT score ≥ 50.

Method: VBM

Scanner: 3 T

Software: VBM8 toolbox of the Statistical Parametric Mapping (SPM) 8

Region-of-interest analysis revealed that gray matter volume in the right dmPFC, bilateral insula and OFC, right amygdala, and left fusiform gyrus showed significant positive correlations with impulsivity in the control group, while no significant correlation was found in the IGD group.

Wang et al. (2015) [37]

IGD group: N = 17 (13 boys and 4 girls), 16.9 ± 2.7 years.

Control group: N = 24 (18 boys and 6 girls), 15.9 ± 2.7 years.

Modified YDQ for internet addiction criteria (answered “yes” to questions 1 through 5 and at least any one of the remaining three questions).

Method: fMRI

Scanner: 3 T

Software: DPARSF3.0 Advanced edition MRImaging toolkit

IGD group showed decreased voxel-mirrored homotopic connectivity (VMHC) between the left and right superior frontal gyrus (orbital part), inferior frontal gyrus (orbital part), middle frontal gyrus, and superior frontal gyrus.

Wang et al. (2015) [53]

IGD group: N = 28 (18 boys and 10 girls), 18.8 (1.33) years.

Control group: N = 28 (20 boys and 8 girls), 19.3 (2.56) years.

Modified YDQ for internet addiction criteria

Method: VBM

Scanner: 3 T

Software: FSL-VBM

IGD group showed:

1) Decreased gray matter volume of the bilateral ACC, precuneus, SMA, superior parietal cortex, left DLPFC, left insula, and bilateral cerebellum.

2) Negative correlation between gray matter volume of the ACC and the incongruent response errors of Stroop task.

Hong et al. (2015) [96]

IGD group: N = 12 (boys), 13.41 ± 2.31 years.

Control group: N = 11 (boys), 14.81 ± 0.87 years.

IAT score ≥ 50

Method: fMRI

Scanner: 3 T

Software: SPM8

IGD group showed:

1) Reduced dorsal putamen functional connectivity with the posterior insula-parietal operculum.

2) More time spent playing online games predicted significantly greater functional connectivity between the dorsal putamen and bilateral primary somatosensory cortices.

3) Significant and specific differences in the dorsal putamen functional connectivity.

Xing et al. (2014) [97]

IGD group: N = 17 (10 boys and 7 girls), 19.1 ± 0.7 years.

Control group: N = 17 (11 boys and 6 girls), 19.8 ± 1.3 years.

IAT score ≥ 50

Method: fMRI (functional connectivity) and diffusion tensor imaging (DTI) tractography methods

Scanner: 3 T

Software: FMRIB’s Software Library (FSL)

IGD group showed:

1) Decreased fractional anisotropy (FA) in the right salience network (SN) tract and no significant differences in functional connectivity compared with the control group.

2) Negative correlation between FA values of the right SN tract and errors during the incongruent condition in a color-word Stroop task (i.e., impaired cognitive control).

Feng et al. (2013) [36]

IGA group: N = 15 (13 boys and 2 girls), 16.93 ± 2.34 years.

Control group: N = 18 (14 boys and 4 girls), 16.33 ± 2.61 years.

Modified YDQ for internet addiction criteria

Method: fMRI

Scanner: 3 T

Software: SPM8

IGA group showed:

1) Higher global CBF in the left inferior temporal lobe/fusiform gyrus, left parahippocampal gyrus/amygdala, right medial frontal lobe/ACC, left insula, right insula, right middle temporal gyrus, right precentral gyrus, left SMA, left cingulate gyrus, and right inferior parietal lobe.

2) Lower CBF in the left middle temporal gyrus, left middle occipital gyrus, and right cingulate gyrus.

Ding et al. (2013) [98]

IGA group: N = 17 (13 boys and 4 girls), 16.94 ± 2.73 years.

Control group: N = 24 (16 boys and 8 girls), 15.87 ± 2.69 years.

Modified YDQ for internet addiction criteria

Method: fMRI

Scanner: 3 T

Software: MRIcroN toolset, SPM5,

and the Resting-State fMRI Data Analysis Toolkit

IGA group showed:

1) Increased functional connectivity in the bilateral cerebellum posterior lobe and middle temporal gyrus.

2) Decreased connectivity in the bilateral inferior parietal lobule and right inferior temporal gyrus.

3) Positive correlation between severity of internet addiction and connectivity in the PCC and right precuneus, posterior cingulate gyrus, thalamus, caudate nucleus, NAc, SMA, and lingual gyrus.

4) Negative correlation between severity of internet addiction and connectivity in the PCC and two areas (right cerebellum anterior lobe and left superior parietal lobule).