Table 2 Detailed illustration of the present ASST procedure Dimension Discrimination 1 914 Phase Session 1 SD CD CDR IDS IDSR Session 2 IDS2 IDSR2 EDS EDSR Media Media Media Media Media Media Media Odors Odors Fine gravel vs. beads Orange Fine gravel Orange Fine gravel Lemon Crumpled tissue Lemon Crumpled tissue Spicy Cardboard Spicy Cardboard Cream Bamboo sticks Cream Bamboo sticks Arrack Beads Arrack Beads Almond Aluminum balls Almond Aluminum balls Vanilla Plastic Vanilla Plastic Rum Polystyrene Rum Polystyrene Psychopharmacology (2011) 214:911–921 Discrimination 2 Orange Beads Orange Beads Lemon Aluminum balls Lemon Aluminum balls Spicy Plastic Spicy Plastic Cream Polystyrene Cream Polystyrene Arrack Fine gravel Arrack Fine gravel Almond Crumpled tissue Almond Crumpled tissue Vanilla Cardboard Vanilla Cardboard Rum Bamboo sticks Rum Bamboo sticks For each trial, mice were presented with either discrimination 1 or 2. In this example at the SD phase, all digging dishes had no odor, and the subjects had to choose the beads as the correct digging medium (in italics). Note that the stimuli are the same for CD and CDR, for IDS and IDR, and for EDS and EDSR contrast to the protocols of Papaleo et al. (2008) and Garner et al. (2006), we divided the whole ASST procedure into two sessions. The reason for using a two-session procedure was that the mice appeared satiated when we attempted to complete all of the phases of testing in 1 day. Therefore, session 1 consisted of a warm-up habituation trial (identical to the last trial of the habituation session) and five phases: (1) simple discrimination (SD), (2) compound discrimina- tion (CD), (3) compound discrimination reversal (CDR), (4) intra-dimensional shift (IDS), and (5) intra-dimensional shift reversal (IDSR). The overall testing time for one animal during this session was approximately 60 to 70 min. Session 2 also consisted of a warm-up habituation trial and four phases: (1) intra-dimensional shift 2 (IDS2), (2) intra- dimensional shift reversal (IDSR2), (3) EDS, and (4) extra- dimensional shift reversal (EDSR). The overall testing time for one animal during this session was approximately 40 to 50 min. Thus, the mice were exposed to a series of increasingly difficult discriminations during which they discriminated within a dimension (the media covering the food reward) that was relevant from the SD phase until the EDS phase. At the EDS phase, the mouse had to start discriminating within a new stimulus dimension (odors), and the previ- ously relevant dimension (media) became irrelevant. This schedule was used for all of the subjects and was based on preliminary results that demonstrated a tendency for better performance when the sequence of dimension change was from the media to odors (data not shown). An example of the entire task is shown in Table 2. Drugs Ketamine (10% aqueous solution of 115.34 mg/ml, Biowet, Poland) and Ro 25-6981 compound [(aR,bS)-a-(4-hydrox- yphenyl)-b-methyl-4-(phenylmethyl)-1-piperidinepropanol