| Category | Description | Articles |
| Population | Small number of subjects in the study | [37, 58, 80, 83, 86, 99, 101, 109–111, 121, 124, 128, 135, 139, 140, 153, 159, 163, 164] | Merged databases are different due to local implementations | [81] | Lack of different stages in AD cohort | [86, 121, 135] | AD cohort includes participants taking antidementia drugs | [81, 83, 163, 164] | Lack of population matching, age, gender, and/or education | [66, 90, 99, 135] | Possible preclinical AD in N cohort | [81] | Prodromal AD was applied in aMCI with Aβ42 | [150] |
| EEG experiment setup | No severe AD as hard to perform EEG recordings | [66] | Presence of dominant alpha activity during EC condition | [80] | Differences in datasets due manual artifact handling | [58, 81, 163] | Low number of electrodes for source localization methods | [37, 82, 163] | Low number of electrodes for connectivity analysis | [83, 145] | Low number electrodes for advanced AAR methods | [84] |
| Reported results | Lack of research for other dementia types | [39, 109, 110, 139, 163] | Lack of longitudinal approach for N, MCI, AD populations | [66, 128, 138, 155, 160, 170] |
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