Time courses of calcium signals in the projection neurons of ants. A) Time courses obtained in 6 glomeruli as in Figure 1B, after stimulation with 11 aliphatic odours and the air control. Odour names are indicated in colour according to their functional group (aldehydes, black; ketones, red; primary and secondary alcohols, blue and green respectively). Odour delivery (1 sec) is indicated as a grey bar. Both excitatory (calcium increase) and inhibitory (calcium decrease) signals were observed, as well as a few temporally complex signals. On the upper left, an activity map (2-octanol) shows both excitatory responses (in shades of red) and inhibitory responses (in shades of blue) on the same lobe. On the upper right, two examples of typical time courses for excitatory and inhibitory signals are given. In each case, an inverse evolution of fluorescence recorded with 340 nm and 380 nm excitations is observed. B) Time course of a measure of odour separability in all recorded ants. The instantaneous Euclidian distance between each odour glomerular pattern and the air control (red curve) gives an indication of how fast the ant olfactory system can best separate an odour from an odourless background (~800 ms). The instantaneous Euclidian distance between the activity patterns obtained for any two odours (blue curve) gives an indication of how fast the ant olfactory system reaches an optimum in its separation power among odours (~600 ms). Both distances are normalized to 1 at their maximum and to 0 just before odour onset. For this reason, they can be under 0 just before the stimulus. C) Same data as B, showing in greater details the evolution of both measures during the stimulus.