Task switching

Spatial attention and switching abilities between two different tasks were measured using an alternative version of the Trail Making Task [20] consisting of three trials (Fig. 2A). In trial 1, numbers from 1 to 26 were displayed on a computer screen and had to be clicked in ascending order as quickly and accurately as possible. Trial 2 consisted of letters from A to Z that had to be clicked in alphabetical order. Trial 3 included both numbers (1–13) and letters (A–M) and participants had to alternately click numbers and letters in ascending order (e.g., 1-A–2-B…13-M). Correctly clicked signs turned green and faded out, incorrectly turned red. The task could be continued only if targets were clicked correctly (green feedback). Each trial was limited to 3 min. Reaction time (RT) for non-switch trials and switch trials were measured. Switch costs were defined as the difference in respond time between switch trials and non-switch trial and were calculated as follows: Switch costs = Switch RT [item2–26]—Numbers RT [item 2–26]—[Letters RT (item 2–13)—Numbers RT (item 2–13)]. Negative switch costs indicating inadequate reactions (at least one of the trials was not completed in time) were considered implausible and were excluded from the analysis.

Cognitive tasks. A Switch task consisting of 3 sections: 1 numbers had to be clicked in ascending order (non-switch). 2 Letters from A to Z had to be clicked alphabetically (non-switch). 3 Numbers and letters had to be clicked alternately in ascending order (switch, i.e., 1-A–2-B–3-C). B 2-back task. Images with fruits and vegetables were displayed on a computer screen. Participants were instructed to press a defined button when an image matched an image 2 trials before. C Tonic alertness. When a white circle appeared on a black computer screen participants had to press a button as quickly as possible, the display of a white cross required no reaction