**3.2 Inclusion criteria & study quality**

Studies were selected for review if they met the following criteria: i) comprised a longitudinal clinical trial with either a randomized controlled trial (RCT) design or uncontrolled clinical trial design (UCT), ii) sample included only healthy individuals not selected against clinical psychiatric criteria, iii) had MRI assessment at least at baseline (before training) and at post-training, and iv) the nature of the intervention met our definition for cognitive training (described above). The qualities of included studies were assessed against CONSORT 2001 criteria for clinical trials (www.consort-statement.org).
