Kinetics of basal current fluctuations. (A–C) Power spectrum analysis of the black (filtered at DC-5000 Hz) traces in Fig. 1, D–F. Note the increase in noise in the 1–15-Hz band (shaded in gray) in the M71 and I7-positive ORNs, which is not observed in the mOR-EG–expressing ORN. (D) Average basal spike firing in the absence of stimulation as a function of basal variance (average of 9–12 ORNs). (E) Average maximal currents elicited by 100 µM of eugenol, acetophenone, and heptanal ORNs obtained from the mOR-EG, M71-GFP, and I7-GFP mouse lines, respectively. Numbers in the bars of the histograms are the numbers of cells recorded from. *, current levels that were statistically different (t test, 0.05 level). Data points are mean ± SEM.