Forum:Psychic monster effects help

I am trying to build a psychic deck. Majority of the effects state "once per turn" does this mean once in my turn? or once per anyones turn? Can I activate these effects in the other players turn. For instance, Power Injector states "Once per turn you can pay 600 life points to have all face-up Psychic-type monsters gain 500 ATK during this turn". Can I activate this in another duelists turn? Any help please? Thanks