Typical recordings lasted for 4.5 ± 5.1 min. Cells were identified as principal neurons based on depth and input resistance (<200 MOhm). For postmortem morphological identification of neurons, mice were perfused following the acute electrophysiological experiment with cold PBS (in mM): NaCl (137), KCl (2.8), KH2PO4 (1.5), Na2HPO4 (8.1), pH7.4, osmolarity (286 mOsm/kg) followed by 4%

formaldehyde solution in PBS. Fixed OBs were cut with a vibratome (Leica, Wetzlar, Germany) selleck screening library and stained with avidin-biotinylated peroxidase (ABC kit, Vector Labs, Burlingame, CA) and the diaminobenzidine reaction. Stained cells, as well as the OB layers (mitral cell layer, MCL; bottom of the glomerular layer, GL), were traced using a Neurolucida system (Micro Bright Field, Williston, VT). Electrophysiological data was analyzed with Spike 2 (Cambridge Electronic Design, Cambridge, UK), MATLAB (MathWorks, Natick, MA). Unless noted otherwise, all recordings were aligned to the sniff cycle (Shusterman et al., 2011). Confidence intervals for circular data were obtained by a Bootstrap method. Briefly, random subsets of data were chosen 100 times from each data set. For each random subset, the deviation of its average phase from the population mean was calculated. These deviations were rank ordered and those at the 5th and 95th ranks were taken as the 90% confidence and interval

of the mean. Such confidence intervals were used to assess the stability of preferred phase under control conditions (see Figure S7). Statistical comparisons of two circular data sets were carried out nonparametrically U0126 clinical trial (Fisher, 1995): Pr=(N2[M(N−M)])∑i=12mi2ni−NMN−M. For each data set the value was calculated, where i = experimental conditions 1 and

2, N = number of all data points, ni = number of data points for each condition, and mi is the number of neurons whose preferred phase was smaller (i.e., ϕ(ij) − ϕ (whole data set) < 0) than the population mean, and M = m1 + m2. Pr values were then compared against the χ2 distribution ( Fisher, 1995) in order to obtain p values. Firing rate models (6 × 107) of the OB network based on key features of the known anatomy (Wachowiak and Shipley, 2006) were constructed from two excitatory principal neurons (one TC and one MC) together with three interneurons (periglomerular cells driven [PGo] and not driven [PGe] by OSN input, as well as a granule cell), with parameters given in Table S1. For each model the overall connectivity architecture was as shown in Figure 6A. The synaptic weight for each connection was chosen randomly from a uniform distribution in the range (0–1). Drawing connectivity parameters from Gaussian distributions with mean 0.5 and SD of 0.2 resulted in essentially identical results as in Figures 6C–6F.