Psychomotor speed was measured with two tests being part of a standardised language independent computerized battery of cognitive tests (CogState1, version 3.0.5). This battery has been validated and shown to be a sensitive indicator of mild impairments in the following cognitive domains: psychomotor speed, attention, working memory and episodic learning and memory (Collie et al., 2001, 2003; Darby et al., 2002). In the tasks participants were asked to pay attention to playing cards on a computer screen. The test battery takes approximately 15 min to complete and is preceded by a practice round. In the simple RT task, which assesses psychomotor function and speed of processing, a single card is presented face-down on the computer screen. The subject is asked to press the spacebar as soon as the card turns face-up. This is repeated 35 times with random time intervals. This task is administered twice – first and last in the test battery – and the mean RT is calculated. In the 2-choice RT task, subjects are asked to indicate whether the turning playing card on the screen is red by pressing either K (“yes”) or D (“no”). The stimulus is repeated 30 times and the mean RT is calculated.
