Baclofen mildly reduces odor-evoked EPSCs for selectively tuned neurons, but strongly blocks the excitatory responses and

thus sharpens the tuning for Selleckchem BI2536 broadly-tuned neurons. In contrast, baclofen exerts similarly effective blockade of odor-evoked inhibitory responses on all neurons irrespective of their excitatory tuning. Because all PNs appear to receive the same amount of excitation from LOT inputs, the authors suggest that intracortical excitations might contribute strongly to the odor-responses of broadly-tuned neurons but may have weak effects on selectively responsive neurons. Together, these studies (Franks et al., 2011 and Poo and Isaacson, 2011) offer several insights into our understanding of the circuit wiring scheme in the piriform cortex (Figure 1) and suggest important roles of recurrent intracortical connections in shaping cortical odor representation. Their results indicate that, although the chance of any pair of PNs forming synaptic connections is low, an individual PN might receive excitatory inputs from thousands of other PNs across a distance

of millimeters. In addition, PNs can activate local GABAergic neurons to generate global inhibition to maintain the balance of cortical activity. In response to an odorant, the bulbar input might activate a small subset of PNs, which then recruits a larger population of PNs and interneurons C59 wnt solubility dmso to generate a complex pattern of excitation and inhibition in the piriform. Some PNs may receive stronger intracortical excitation than others and thus exhibit broader olfactory tuning. Results from these two new studies suggest additional experiments to pin down the exact wiring pattern in the piriform cortex. Do all PNs

play equal roles in intracortical association? Morphologically identified PNs exhibit highly diverse olfactory tunings in terms of both excitation and inhibition in an awake mouse (Zhan and Luo, 2010). Both new studies indicate heterogeneity among PNs in receiving intracortical excitation. In vivo recordings show that broadly tuned neurons tend to Montelukast Sodium be more frequently activated by odor-elicited intracortical excitation (Poo and Isaacson, 2011). Consistently, individual PNs appear to receive quite variable amount of recurrent excitation in slice preparations (mean ± SD: 441 ± 334 pA; Franks et al., 2011). It remains unclear whether PNs uniformly extend long-range axonal terminals to synapse on thousands of other PNs, or whether some subtypes of PNs exert much stronger influence on other PNs. This may be tested by serially activating small subset of ChR2+ neurons with focal illumination and mapping area-specific effects on a group of ChR2− neurons. Interneurons represent another major class of cortical neurons. Although the interneurons are labeled as a single type of inhibitory neurons in the diagram (Figure 1), they can be divided into various subtypes based on their morphological, neurochemical, and functional features.