As with extracellular data, we normalized cortical EPSPs to total MOB output by dividing by the number of uncaging sites. Coactivating additional glomeruli led to an increase in the net “per glomerulus” synaptic input (Figure 6H). As noted above, supralinearity appeared to emerge in PCx rather than MOB, since M/T firing was independent of uncaging pattern size (Figure S3H–S3L). Supralinearity could potentially arise at the single-neuron level through nonlinear synaptic integration mechanisms, at the network level through ABT-737 neural circuit interactions, or both. We analyzed supralinearity at the level of single cells, directly comparing EPSPs for both multiglomerular patterns and individual component

sites. Multisite patterns often generated clear EPSPs even when input from any component site

was negligible (Figure 7A), suggesting that supralinearity may arise intracortically via recurrent input from other PCx neurons directly driven by multisite patterns (Figure 3; see Haberly, 2001). Averaged data showed pattern-evoked EPSPs were consistently greater than the sum of components Ibrutinib (Figures 7B and 7C; significant supralinearity in 5/6 neurons; p < 0.05, t test). In addition, although the size of predicted EPSPs was typically minimal, multisite patterns reliably generated substantial synaptic input (Figure 7C), suggestive of substantial cortical amplification of weak MOB inputs. Together, our data reveal highly cooperative PCx responses to multiglomerular input, imparting strong sensitivity to combinatorial MOB activity that is the hallmark of sensory responses. The initial representation of odor information Adenosine in the brain is organized by the topographic map of OR input to the MOB. We used the OR map to assess the circuit mechanisms for odor processing in anterior PCx, which have remained enigmatic. Using in vivo photostimulation to drive highly defined patterns of cortical input, we found that individual PCx neurons fired in response to distinct patterns of

coactive MOB glomeruli. Intracellular measurements revealed a distinct subset of relatively weak glomerular inputs to each cell. Together, the combination of network connectivity, synaptic strength, and cooperativity between glomerular inputs allows PCx neurons to detect specific patterns of MOB output, providing a mechanistic basis for cortical processing of complex odor stimuli. Successive processing stages often represent increasingly complex features in the sensory environment (Hubel and Wiesel, 1959). What are the higher-order characteristics of chemical stimuli encoded in PCx? Virtually all odors comprise diverse chemical attributes that bind multiple ORs and drive distributed MOB activity patterns (Lin et al., 2006 and Soucy et al., 2009). Several findings indicated that PCx neurons detect higher-order glomerular combinations embedded within such patterns.