In sharp contrast, adrenergic blockade elicited a clear left shift in d′ for synchronized spike trains, as would be expected for loss of magnitude of the divergence in z-scores (leftward shift in green [adrenergic] line compared to red [control] line in Figure 7D). Interestingly, and learn more consistent with the left shift in d′, for odor-divergent pairs there was a sharp reduction in the odor-induced change in percent of synchronized spikes between adrenergic block and control (Figure 7B, also see Figure S4). Thus, the odor-induced changes in synchronized firing in the presence

of adrenergic block are entirely due to changes in firing rate of the reference PR-171 price units, not changes in the percent of synchronized spikes. Our findings indicate that the firing of synchronized spikes between groups of SMCs, the second-order neurons in the olfactory circuit, carries information on odor value or on other reward signals, such as attention and vigilance (Wallis and Kennerley, 2010). An observer can make a decision on odor value based on whether the number of synchronized spikes fired by SMCs increases or decreases in response to an odor. Thus,

placing a vertical line at Δz = 0 in Figure 4Aii allows successful discrimination between rewarded (Δz > 0) and unrewarded (Δz < 0) odor based on synchronized firing responses to odors (solid lines). In contrast, there is no vertical line that ensures successful determination of odor value based on the odor responses of the units that make up the synchronized firing Aldehyde dehydrogenase pair (Figure 4Aii, broken lines). Interestingly, odors, like tastants, vary in whether they are naturally perceived as attractive or repulsive. Based upon this observation, we would predict that naturally repulsive

odors would yield decreases in synchronized firing, whereas attractive odors would yield increases, with reversals as the animal is trained otherwise. The observed learning-induced plasticity in the OB that provides information on odor value could contribute to downstream plasticity, decision-making, or the estimation of expected outcomes used in prediction error calculations. The precise timing for synchronization of spikes in different SMCs (spikes that lag by <250 μs; Figure 2) raises the question of whether this is due to common source noise from a biological action (e.g., grinding of teeth or licking). An advantage of using the go-no go task is that behavior is stereotyped for hit trials wherein the animal must lick during the RA. We asked whether biological actions during this stereotyped behavior in hit trials could have yielded the increase in synchronized firing observed during responses to the rewarded odor.