A) Place learning (PL): In a designated corner for each mouse, a nosepoke opened the left door once during a visit. Thereby the animals were given access to 300 mM sucrose (rewarded corner) during two drinking sessions per night (23:00–24:00 and 04:00–05:00). The right door in the same corner remained closed. In the other three corners, a nosepoke opened the right door which gave access to water (unrewarded corner) once during the two drinking sessions. The left door remained closed during the rest of time. The corner in which reward was given was randomized and individual designated to each mouse.
(B) Reversal learning during drinking sessions (revPL): The same protocol as PL except that the respective corner giving access to sucrose was the diagonal opposite.