MFCTA Science Update

Mapping the Sense of Smell: A New Spatial Code in the Mouse Nose

The sense of smell has long been regarded as one of the most mysterious sensory systems. Unlike vision, hearing, and touch—where spatial maps are clearly recognised in the eye, cochlea, skin, and brain—olfaction was traditionally thought to be organised in a much looser way. A new study now challenges this view by showing that the mouse nose contains a highly organised “smell map”, with olfactory receptor neurons arranged in predictable spatial patterns across the olfactory epithelium.

The researchers found that olfactory receptor neurons are not randomly distributed. Instead, neurons expressing particular smell receptors occupy characteristic positions along the dorsal–ventral axis of the nasal olfactory epithelium. These receptor populations form overlapping horizontal bands or stripes, creating a reproducible map across animals. This suggests that smell, like other senses, has a structured anatomical organisation from the very first stage of sensory detection.

To generate this map, the investigators used advanced single-cell sequencing and spatial transcriptomics. These techniques allowed them to identify which olfactory receptor was expressed by each sensory neuron and where that neuron was located within the nasal tissue. By analysing millions of neurons across hundreds of mice, the study provides one of the most detailed spatial maps of a sensory tissue to date.

A particularly important finding was that the organisation in the nose appears to correspond with the organisation in the olfactory bulb, the first major brain centre for smell processing. The olfactory bulb lies at the underside of the frontal lobe, just above the nasal cavity, and receives signals from olfactory receptor neurons through the cribriform plate. This alignment suggests that spatial order in the nose may be preserved and interpreted by the brain.

The study also provides insight into how this map may be established during development. The researchers identified retinoic acid signalling as a key organising influence. A gradient of retinoic acid appears to help determine which receptor a neuron expresses according to its position. When retinoic acid levels were experimentally altered, the receptor map shifted, supporting the idea that chemical gradients help pattern the olfactory system.

Although this work is based on mice and remains basic science, it has important implications. Understanding how the olfactory system is normally organised may help future research into anosmia, post-viral smell loss, ageing-related olfactory decline, and smell changes associated with neurodegenerative disease. It may also inform future attempts to regenerate or repair olfactory tissue after injury or infection.

Take-home message

This study reveals that the nose contains a precise and reproducible map of smell receptor neurons. Rather than being randomly scattered, olfactory neurons are spatially organised in overlapping bands, shaped in part by retinoic acid signalling and mirrored in the olfactory bulb. The discovery changes our understanding of smell from a loosely arranged chemical sense to a spatially organised sensory system.

MFCTA summary line

The mouse nose contains a hidden “map of smell”, showing that olfaction is more spatially organised than previously believed — a discovery that may reshape future research into smell loss and sensory regeneration.

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