007, p = 0.159), odor stimulus (F1,11.01 = 0.73, p = 0.411), or target-by-stimulus interaction (F1,11 = 0.914, p = 0.36) on inspiratory sniff volume (data not shown). Thus, the only salient cognitive difference between target A and target B runs was the attentional focus of the subject. We first examined whether odor-specific ensemble patterns were formed prior to the arrival of the stimulus.

The central hypothesis was that prior to odor onset, spatial activity patterns would be more correlated between same-target conditions TGF-beta inhibitor than between different-target conditions in brain regions encoding the odor target. Thus for example, if a given ROI reflected the targeted note, the prestimulus pattern in response to condition A|A would correlate more strongly to A|B (same target but different stimulus) than to B|A (different target but same stimulus). Conversely, in a region encoding the actual odor stimulus, the pattern in response to condition A|A would correlate more strongly to B|A (same stimulus but different PLX3397 mouse target) than to A|B (different stimulus but same target). In this manner, one could test a distinct contrast (same target/different stimulus correlations versus same stimulus/different target correlations) to look

for both target-related and stimulus-related effects, both before and after odor onset (Figure 3A). These analyses were computed for target A runs and for target B runs in the pre-and poststimulus time bins and entered into a three-way Astemizole repeated-measures ANOVA with the factors “target run” (A or B), “pattern type” (target-related

or stimulus-related pattern), and “time” (pre- or poststimulus onset). Because no region exhibited a significant effect of target run (all p’s > 0.2), data are shown collapsed across A and B runs (for non-collapsed data, see Figure S1). In line with the idea that prestimulus, odor-specific patterns exist in the olfactory system, fMRI ensemble correlations between same-target conditions were significantly higher than correlations between different-target conditions (Figure 3B). In APC and OFC, there was a significant effect of pattern type (APC: F1,11 = 30.933, p < 0.0001; OFC: F1,11 = 13.437, p < 0.004) in the target direction, whereby same-target conditions were more correlated than different-target conditions (APC: T11 = 5.6, p < 0.0001; OFC: T11 = 3.67, p < 0.003). In APC, there was also a significant pattern type-by-time interaction (F1,11 = 5.79, p < 0.035) in which the same-target (compared to different-target) correlations were larger in the prestimulus bin than in the poststimulus bin (pre: T11 = 6.3, p < 0.0001; post: T11 = 1.99, p < 0.07). There was no such interaction in OFC (p = 0.3). Neither MDT nor PPC exhibited a significant main effect of pattern type or time (p's > 0.1).