1 / Simple discrimination / Cinnamon/Sawdust / Clove/Sawdust
2 / Compound discrimination / Cinnamon/Sawdust
Cinnamon/Sand / Clove/Sand
Clove/Sawdust
3 / Reversal 1 / Clove/Sand
Clove/Sawdust / Cinnamon/Sawdust
Cinnamon/Sand
4 / Intradimentional shift / Coriander/Aluminium
Coriander/Paper / Herbs/Paper
Herbs/Aluminium
5 / Reversal 2 / Herbs/Paper
Herbs/Aluminium / Coriander/Aluminium
Coriander/Paper
6 / Extradimentional shift / Nutmeg/Raffia
Cumin/Raffia / Cumin/Plastic
Nutmeg/Plastic
7 / Reversal 3 / Nutmeg/Plastic
Cumin/Plastic / Cumin/Raffia
Nutmeg/Raffia
Table S1: Description of the discrimination stages.
Pairs of stimuli of each combination are presented as odour/digging medium. The relevant dimension is the odour for the first 5 discrimination stages, then the digging medium for the last two. The discrimination stages were presented in a fixed order for all rats: (1) A simple discrimination with the bowls differing only in odours. (2) A compound discrimination, where the second, but irrelevant, dimension was introduced (digging medium). (3) A reversal (reversal 1) of the previous discrimination. (4) An intradimensional shift in which there was a total change of odour/digging medium combination. (5) A reversal (reversal 2) of the previous discrimination. (6) An extradimensional shift in which again there was a total change of odour/digging medium combination and in which the digging medium became the relevant dimension. (7) A reversal (reversal 3) of the previous discrimination. The correct stimulus is shown in bold, paired with either stimulus from the irrelevant dimension. During the course of the test, the relevant and irrelevant combinations were identical for all rats. The left–right position of presentation in the test apparatus was a pseudorandom series determined in advance.
Antibody characterization: Monoclonal mouse anti-NeuN antibody (MAB-377; Chemicon) is raised against undetermined nuclear proteins of neurons (NeuN). This antibody recognizes two or three bands in the 46–48-kDa range and possibly another band at approximately 66 kDa. Even though the sequence of the immunizing antigen(s) has not been established yet, this antibody has been shown to stain neurons exclusively, both in vivo and in vitro, recognizing most neuronal neuronal cell types throughout the central nervous system of numerous vertebrates (for review see Sanchez et al., 2009). Mouse anti-GFAP (G3893; Sigma-Aldrich) is a monoclonal antibody obtained from mouse ascites fluid from clone G-A-5, a fusion of mouse myeloma cells and spleen cells from an immunized mouse, using purified GFAP from pig spinal cord as the immunogen. This antibody is known to recognize the glial fibrillary acidic protein of 50 kDa expressed in astrocytes (for review see Del Carmen Gómez-Roldán et al., 2008).