, 2006). In rodents, eliminating ORN activation or decoupling nasal airflow from respiration disrupts respiratory rhythms in the olfactory pathway in favor of nasal airflow rhythms (Grosmaitre et al., 2007, Sobel and Tank, 1993 and Spors and Grinvald, 2002). Thus, olfactory network dynamics are primarily driven by the dynamics Talazoparib mouse of inhalation-driven ORN input (Figures 2C and 2D). For example, the rise-time of odorant-evoked EPSPs in mitral/tufted (MT) cells—the principal OB output neuron—of anesthetized rats is approximately 100 ms, similar to that of the ORN response transients (Cang and Isaacson, 2003 and Margrie and Schaefer, 2003). MT cells also show variation in temporal

response patterns Selleck VX-770 (e.g., latency, rise-time and duration of an excitatory burst) that is unit and odorant specific (Bathellier et al., 2008 and Macrides and Chorover, 1972) and varies over a range similar to that of ORNs (Carey and Wachowiak, 2011).

Finally, pyramidal neurons in piriform cortex (PC)—a major target of OB output—also show strong inhalation-coupled dynamics in their spike output and in subthreshold synaptic inputs (Poo and Isaacson, 2009 and Rennaker et al., 2007; Figure 2D). Given the temporal constraints on ORN responses imposed by respiration it seems likely that postsynaptic networks will be optimized for such input dynamics. Indeed, while the canonical view of the OB network has been that it shapes Adenylyl cyclase MT response properties in the spatial domain—e.g., relative to activity in other glomeruli and their associated MT cells (Johnson and Leon, 2007 and Yokoi et al., 1995), recent data suggest that postsynaptic processing may primarily function to shape responses in the temporal domain relative to inhalation-driven bursts of input (Figure 3). Work supporting this view comes largely from experimental paradigms far removed from “active” sensing. For example, in OB slice preparations, delivering patterned olfactory nerve stimulation at frequencies that mimic resting respiration amplifies MT

responses to ORN input and leads to increased synchrony of MT firing and the emergence of gamma-frequency oscillations in MT cell membrane potential (Hayar et al., 2004b and Schoppa, 2006b). Neurons in PC—the major cortical target of OB output neurons - also appear optimized to process information in a temporal domain organized around inhalation-driven bursts of input from MT cells. MT cell axons from the OB provide direct but selective excitation to pyramidal neurons in PC while also driving more widespread feed-forward inhibition via GABAergic local interneurons (Poo and Isaacson, 2009). For sparse and temporally unstructured MT cell inputs to PC, this strong feed-forward inhibition creates an extremely short (5–10 ms) time window during which pyramidal neurons may integrate M/T inputs from the OB.