Time frame: Period 1 at 3 visits,(post 1),(post 2),(post 3), in a 5-day (maximum 8 day) period. Period 2 at 3 visits,(post 1),(post 2),(post 3), in a 5-day (maximum 8 day) period.
Attentional standardised composite score: Standardised speed of performance score. Higher Score=better performance. Score range minus infinity to plus infinity. Measured at baseline (before study drug administration) and in Period 1 at 3 visits,(post 1),(post 2),(post 3), in a 5-day (maximum 8 day) period. (Last test day not earlier than after 10 days of randomised)and in Period 2 at 3 visits,(post 1),(post 2),(post 3), in a 5-day (maximum 8 day) period. Last test day not earlier than after 10 days of crossover treatment.