One particular methodological challenge for our meta‐analytic approach is that not all cohorts use the same electrode layout and reference electrode during recording. From the 1990s onwards, the number of recording channels has steadily increased, with the most recent cohorts measuring at least 30 channels or more. It is hardly debated that increased density provides highly valuable information on individual differences in brain function, in both health and disease. The earlier studies, however, recorded with 5, 7, 14, or 15 channels. Sparse layouts such as these greatly reduce the possibility to provide more localized brain activity measures.
