Figure 1. Counterbalancing schema. During surgery, only two lists (target words) are presented. The postoperative memory test consists of all four lists (target and distractors; appendix 2). For example, if patients had been assigned randomly by the computer to group 3, they would have been presented lists 1 and 3 during surgery as target words, and they would have been tested on lists 3 and 4 in the inclusion part and on lists 1 and 2 in the exclusion part.