Odor representations are structured by heterogeneous tuning and concentration-dependence of functionally distinct olfactory sensory neuron subpopulations.

In anesthetized mice, OSN axon terminal glomerular maps for 59 odorants show exceptionally sparse, narrowly tuned responses at the most-sensitive concentrations, then broaden heterogeneously with concentration.

• Why it matters: It remains unclear how glomerular maps encode odorant features like chemical structure and concentration, and whether OSN subtypes impose a structured, lower-dimensional representation.
• What they did: Using GCaMP6 imaging in the olfactory bulb, the same 59 odorants were tested across three concentration regimes, with “low” and “high” differing by 25-fold and 2–5 log units above the most-sensitive regime.
• The result: Increasing concentration broadened tuning of OSN inputs in a heterogeneous way, captured by classifying glomeruli into several subpopulations with distinct consensus tuning profiles that stayed spatially localized even at the highest concentrations.

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