Varying the identity of active glomeruli often produced markedly different responses in individual PCx cells (Figure 4B). Testing with a series of multisite stimuli revealed pattern-selective firing in many neurons (Figure 4C). Pattern detection by PCx reflected cortical processing rather than differences

in potency of our test stimuli, since all patterns were equally effective when averaged across the population sample (Figure S4; p > 0.2, Kruskal-Wallis test). We evaluated http://www.selleckchem.com/products/PF-2341066.html pattern sensitivity for each cell using a selectivity index (lifetime sparseness, SL) to quantify the extent to which responses were driven solely by a single pattern (SL = 1) versus equally by all patterns (SL = 0). For the majority of neurons, SL selleck chemical was significantly higher than predicted by a randomly shuffled dataset (p < 0.05; Figure 4D; see Experimental Procedures). Pattern

selectivity was also consistently higher for measured versus shuffled data at the population level (Figure S4). Single PCx neurons thus appear to detect specific patterns of coactive MOB glomeruli. Furthermore, we also found that the PCx population detected a wide range of MOB patterns. Different neurons had different response profiles for the same set of synthetic stimuli (Figure 4C), indicating detection of distinct glomerular combinations. To quantify the diversity in pattern detection across cells, we calculated correlation coefficients for all pairs of response profiles for all neurons, and repeated this analysis

for shuffled data. Measured response profiles were consistently more dissimilar than shuffled data (Figures 4E and S4; p << 0.01 for patterns with 4, 9, and 16 sites; Kolmogorov-Smirnov test; n = 14–39 cells). Taken together, these results demonstrate that the PCx population collectively samples a diverse range of possible from combinations of MOB glomeruli. The circuit mechanisms supporting glomerular pattern detection by PCx neurons were not apparent from extracellular recordings. We asked whether this computation arose from the circuit architecture mapping MOB output onto individual PCx cells. Each neuron in PCx will decode MOB activity based on the number and identity of glomeruli providing it with direct synaptic input, and on the strength of those inputs. To test network connectivity on this cellular scale, we combined single-site scanning photostimulation of MOB with in vivo intracellular recordings of subthreshold synaptic responses in PCx. For each PCx neuron, we classified MOB sites as synaptically connected if they generated time-locked excitatory postsynaptic potentials (EPSPs) that were ≥2 standard deviations above resting membrane potential fluctuations (during a 150 ms analysis window; see Experimental Procedures). Although categorizing EPSPs as mono- or polysynaptic is potentially ambiguous, our data from parallel extracellular experiments showed little or no evoked firing in PCx under the same conditions (Figures 2 and S2).