We ask whether synchronized firing conveys information on odor

identity (“What is the odor?”), or alternatively, value (“Is it rewarded?”). In addition, noradrenergic (NA) modulation is known to play a role in new olfactory stimulus/reward association (Bouret and Sara, 2004 and Doucette et al., 2007), and we ask whether NA antagonist application in the OB affects synchronized spike odor responses of SMCs to rewarded and unrewarded odors in the go-no go behavioral task. We find that responses of synchronized SMC spikes to odors convey information on odor value (or Selleckchem Vismodegib a related reward signal), and that the differential synchronized spike response to rewarded and unrewarded odor is not as robust in the presence of inhibitors of NA modulation of the OB. Thus, the olfactory system stands out from other sensory systems in that information on stimulus value

is found in the MC that is one synapse away from the sensory neuron, in the same place in the circuit as would be a bipolar cell in the visual system or a spiral ganglion cell in the auditory system. Mice were implanted with two eight-microelectrode arrays targeted to the MC layer (Figure 1A). During each trial in the go-no go task, thirsty mice were asked to respond to a rewarded odor by licking a tube, and they received a water reward if they licked at least once in the last four 0.5 s periods of the trial (the Resminostat response area [RA]; see Figure 1Bi; no reward for the unrewarded odor). The sniffing behavior of animals during this task is illustrated Pazopanib in Figure 1Bii. Consistent with previous reports (Wesson et al., 2008), animals showed an increase in sniffing frequency in anticipation of odor presentation. Sniffing frequency started differing between successful rewarded and unrewarded odor trials at ∼1.7 s

in the middle of the decision-making period, when mice steadily reduced their breathing rates to a final frequency of 2–3 Hz after the water reward. Figure 1C shows an example of how a mouse learns to respond in a session wherein the animal is presented with a new pair of odors. Mice stop responding to the unrewarded odor because the licking entails considerable effort that is not rewarded with water. Mice learned to respond reliably (more than 80% correct) within 3–6 blocks of 20 trials (10 rewarded and 10 unrewarded) (Slotnick and Restrepo, 2005). We recorded from 345 single units and 820 multiunits in the MC layer of eight animals in 67 separate sessions (39 first day and 28 reversals). In recordings from mice performing odor discrimination, we find precise synchronization between a subset of spikes (Figure 2). Figure 2A shows precise spiking for three SMCs, and Figures 2B1 and 2B2 show the histograms of interspike lags.