Schematic diagram of the models.

<p>(A) This circuit, based on results obtained <i>in vivo</i>, contains feedback inhibition between the KCs and GGN. (B) This hypothetical circuit contains feed-forward inhibition from the PNs to GGN inhibiting the KCs. (C) Left: Intensity of odor input received by each of the 300 PNs for representative odor concentrations (higher concentrations activate more PNs). Right: Different odors activate different sets of PNs; the two solid lines represent similar odors (activating largely overlapping subsets of PNs), and the dashed line represents a very different odor (activating a largely separate subset of PNs).