It has been reported from in vitro investigations that MCs and TCs that belong to a common glomerulus exhibit

synchronous activities (Ma and Lowe, 2010). In our hand, a condition similar to this situation may occur during strongly excitatory odor presentations, where MC firing patterns become similar to that of TCs. In other circumstances, it is likely that possible synchrony between MCs and TCs might be overridden by feed-forward inhibition by OSN-PGo-MCs, as well as entrainment of TCs by OSNs rather than mutual excitation. In explaining the temporal patterns of TC and MC activations observed, on first glance it seems paradoxical that TCs (as well as MCs during strong excitatory odors) are driven during

exhalation. However, there is a substantial delay following the inhalation onset to OSN discharge, due to odor molecules binding to olfactory www.selleckchem.com/screening/autophagy-signaling-compound-library.html receptors and the relatively slow transduction (Duchamp-Viret et al., 1999). Thus, our results are highly consistent with the notion that the previous inhalation cycle drives depolarization or AP discharge, more than 50–100 ms after the onset of inhalation, in a concentration-dependent manner (Carey et al., 2009). For modest odor concentrations, this implies that MCs lag behind the odor stimulus by approximately half a sniff cycle. Consistent with the rapid responses reported with unit recordings (Cury and Uchida, 2010; Carey and Wachowiak, 2011; Shusterman et al., 2011), TCs in our hands can show an onset in firing rate BTK inhibitor cost increase as early as 85 ms after the start of inhalation, while, naturally, the average spiking phase occurs later (Figure S5). That principal neurons can couple differentially to sniffs has also been noted recently, especially when analyzed over a wide range of sniff frequencies

(Carey and Wachowiak, 2011). It is tempting to speculate that the two types of M/TCs reported may indeed correspond to MCs and TCs. In addition, the observed diversity of responses between MCs and TCs may underlie the finding, and that principal neurons that belong to a common glomerulus undergo diverse phase changes in response to odors, while showing correlated firing rate changes (Dhawale et al., 2010). The differential excitatory and inhibitory inputs onto principal neurons would allow olfactory bulb circuits to diversify M/TC activity, instead of simply reflecting OSN inputs, and thus provide olfactory cortex with more processed signals. MCs and TCs are known to differ in axonal projection patterns in the olfactory cortex (Haberly and Price, 1977; Nagayama et al., 2010). Where they overlap anatomically, the mechanism described here will allow distinguishing the two streams of information, by way of temporal characteristics.