, 2007, Doucette and Restrepo, 2008 and Slotnick and Restrepo, 2005). All mice were first trained to distinguish 1% isoamyl acetate versus 1% cumin PS-341 datasheet aldehyde (v/v in mineral oil). The animal’s performance was evaluated in blocks of 20 trials (10 rewarded and 10 unrewarded, presented at random). Each block’s percent correct value represents the percent of trials in which the odors were correctly discriminated

and associated with the appropriate behavioral action. Each session included 6–10 blocks of 20 trials. Once the animals learned to discriminate between isoamyl acetate and cumin aldehyde, they were ready for the novel odor discrimination task described below. As described in the Supplemental Text, we screened novel odors that presumably would stimulate glomeruli in the ventral surface of the OB (the electrodes were targeted to this area of the bulb). Choice of odors is described in the Supplemental Text. In order to screen these odors in a behaviorally neutral setting, an 8 × 8 × 13 cm chamber was constructed wherein the mouse was exposed learn more passively to odors. Odors were introduced on a constant background odor stream for 2 s with an intertrial interval

of 60 s. Odors were screened in groups of 12 or 15 per session. After a session the data were analyzed overnight and the best two odors (odors A and B) were used in the subsequent odor discrimination task. The odors shown in italics in Table S1 were found to elicit responses more often than the others. Once we identified responsive novel odors A and B, we proceeded the next day with a novel odor pair discrimination task. As in previous studies, in order to make the odor discrimination task difficult, we asked mice to discriminate between odor mixtures (Doucette et al., 2007 and Doucette and Restrepo, 2008). Odor mixtures 4-Aminobutyrate aminotransferase have been employed in several studies of the speed of olfactory

processing (Abraham et al., 2004 and Uchida and Mainen, 2003) and odor similarity determinations (Doucette et al., 2007 and Kay et al., 2006). In our behavioral paradigm the animals learned to discriminate between odor A and a 1:1 mixture of odor A:odor B at an overall concentration of 1% by volume in mineral oil. Measurements using a photoionization detector indicated that odors arrived at the chamber at ∼0.3 s after routing of the odor into the port (mini-PID; Aurora Scientific Inc., Aurora, ON, Canada). Six animals were implanted bilaterally with multielectrode arrays containing a central cannula for adrenergic drug delivery. Multielectrode arrays with cannulae were constructed in a similar 2 × 4 pattern as described above with the addition of a 23G stainless steel tube in the center of the array terminating 2 mm above the electrode tips so that it would sit above the bulb while the electrodes were implanted within the bulb as described above. For adrenergic drug delivery we used the same procedure as in a previous publication (Doucette et al., 2007).