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Fig. 1 Properties of fast-spiking inhibitory interneurons in pDp (A) Lateral view of the adult zebrafish brain and coronal cross-sections of the telencephalon (Tel), showing pDp. OB, olfactory bulb; TeO, optic tectum; Dm, Dc, and Dl, medial, central, and lateral dorsal Tel, respectively. (B) Marker expression in pDp of 212C/dlx double-transgenic fish (Tg[SAGFF212C:Gal4,UAS:mCherry,dlx4/6:GFP], maximum-intensity projection). (C) Optogenetic stimulation of interneurons and whole-cell patch-clamp recording of IPSCs and EPSCs in principal neurons. (D) Mean IPSCs (0 mV) and EPSCs (?60 mV) evoked by 10 0.5-ms full-field blue-light pulses (457 nm, blue bars, 20 Hz) in 212C-Chr2YFP (n = 4) and dlx-Chr2YFP (n = 2; see also Figure S1F). Shading: SEM. (E) Firing patterns of interneurons (GFP+) and a principal neuron (GFP?) evoked by current injections. (F) Mean firing rates as a function of injected current. Shading: SEM. (G) Medial olfactory tract (mOT) stimulation and whole-cell recording in pDp. (H) EPSC latency distribution for interneurons and principal neurons. dlx:GFP+ latencies, but not 212C-GFP+ latencies, were longer than the corresponding GFP? latencies (Wilcoxon rank-sum test: dlx:GFP+: p = 0.0003, n = 27 vs. dlx:GFP?, n = 21; 212C-GFP+: p = 0.63, n = 34 vs. 212C-GFP?, n = 53). Squares: mean ± SEM. (I) Responses of 50 randomly selected GFP? (left) and dlx:GFP+ (right) cells to two amino acid odors (10?5 M). (J) Odor-evoked firing rates inferred from Ca2+ signals averaged over all trials (n = 2), odors (n = 12), and neurons (212C-GFP: n = 1515 GFP? and n = 50 GFP+ from N = 5 fovs; dlx:GFP: n = 1750 GFP? and n = 65 GFP+ from N = 12 fovs). Shading: SD. (K) Mean rank-ordered tuning curves of GFP+ (interneurons) and GFP? (principal) neurons. Shading: SD. (L) Lifetime sparseness of odor responses (same neurons as in J; Wilcoxon rank-sum test; 212C: p < 10?6; dlx: p < 10?6). Circles: median.