Fig. 4

The figure shows the experimental design of treatment groups: experimental group and comparator group. Randomisation process(D1), deviations from intended interventions(D2), missing outcome data(D3), measurement of the outcome(D4), selection of the reported result(D5) indicate five aspects where the risk of bias can arise in a study. The risk signals are in green (low risk), yellow (some concerns), red (high risk). UA: upper alpha; NF: neurofeedback; SMR: sensorimotor rhythm; NA: not available