Extended Data Fig. 4: Temporal features of glomerular response to complex odour extracts.

a, Response of three target glomeruli to 1X concentrations of the given stimuli (same data summarized in Fig. 3h, i). Coloured lines and grey shading show mean ± SEM response (n = 5 mosquitoes). Red arrows under each trace mark desorption (heating) onset. Y-axis scale bars indicate normalized df/f. The biphasic responses seen for B and H and the delayed responses seen for A are likely a technical artifact of thermal desorption odour delivery, resulting from delayed release of a few key compounds (see b–c). b, Overlay of H responses from (a), recoloured to distinguish the early (brown) and late (purple) peaks. Schematics below show the human-odour puff shape estimated with a PID (Extended Data Fig. 3c) and the inferred timing of release of three major aldehyde components (Extended Data Fig. 3d, e). c, Correlations between the area under the peaks in (b) and the relative abundance of major aldehydes in the respective stimuli. Dashed lines show linear regressions. The early H peaks are significantly correlated with the abundance of medium-chain aldehydes (which are fully released within the first 10 s), while late H peaks are correlated with the abundance of long-chain aldehydes (which take 20–40 s to fully desorb). Taken together, the biphasic response of the H glomerulus is therefore likely caused by the different release dynamics of medium- and long-chain aldehydes. The late peaks seen in B and A traces may also be caused by delayed release of strong activators. However, other temporal features of these responses, including the prolonged tonic nature of the A response, are biological, since we saw them both here and when single synthetic odorants were delivered in a more traditional way (Extended Data Fig. 7). To account for temporal artifacts, we always report glomerular responses as area under the full df/f curve (rather than peak df/f). We do not expect this to significantly impact our findings as the responses of olfactory sensory neurons to different compounds and their mixtures are mostly additive in insects²¹.

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