Characterization of calcium transients observed in response to optogenetic stimulation. A and B: Summary of different response types. Stimulation is indicated by the gray bar and consists of 20 light pulses (50 µW/mm2, each of 2 ms duration) delivered at 30 Hz. A: Example neuron pairs, simple responses. (i) PF-LCre to SMPL-L. (ii) GL-N1 to P-EN1. (iii) GL-N1 to L-Ei. B: Example neuron pairs, unclear responses. (i) E-PG to P-F3N2d. (ii) Δ7 to P-F1N3. (iii) Δ7 to P-EG. In A and B, all responses, expressed as ΔF/F0, are baseline subtracted except for the inhibitory response in Aii. Scale bar 2 s. C: Example of statistics computed on individual runs and cell pairs characterizing: (i) average response shape, (ii) reliability of the response, and (iii) response sensitivity. D: Using the distribution of statistics from non-overlapping controls to assign classes to the responses: distributions of response amplitudes and reliability as measured by the scaled normalized integral (the median of the integral normalized to the baseline and scaled so that the dataset spans the [-1,1] range) and the between-flies correlation (see Materials and Methods). Each point corresponds to a different cell pair (median statistics across flies). Control unconnected pairs are shown in blue, and same-cell-type-stimulation in orange. Responses considered significantly different from the control sample (p<0.01, see Materials and Methods) are circled. Video Data attached : videos corresponding to PF-LCre to SMPL-L (SuppVideo1, also shown in Ai), GL-N1 to P-EN1 (SuppVideo2, also shown in Aii) and E-PG to PF-LCre (SuppVideo3, not shown in the figure) to illustrate different type of responses. Top left : average projection of the fluorescence movie with the outline of the ROI used to calculate the fluorescence. Top right : cell pair considered . The red box outlines the approximate location of the region imaged.