For roughly 30 years, biology students have learned the same tidy diagram of the inside of the nose: four broad zones, each peppered with smell receptors in no particular order. Two studies published in Cell in May 2026 replace that picture with something far more precise. (Note: the DOI for this Cell paper has not been independently verified and may not resolve until the publisher finalizes indexing.) Using a high-resolution imaging method called MERFISH, researchers mapped all ~1,100 olfactory receptor genes in the mouse nose and found that each one sits in a specific, narrow stripe, not a vague zone, and that the pattern is nearly identical from one animal to the next.
The discovery suggests the brain may use a receptor’s physical address inside the nose as part of the code for identifying a smell, an idea the old four-zone model never accounted for.
What the new map actually shows
MERFISH (Multiplexed Error-Robust Fluorescence In Situ Hybridization) lets scientists light up hundreds of different RNA molecules in a single tissue slice without grinding the tissue up first. That matters because earlier methods, including bulk sequencing and standard single-cell RNA-seq, destroy the spatial relationships between cells. You learn which genes are active but not where in the tissue they were active.
Applied to the mouse olfactory epithelium, the thin sheet of tissue lining the upper nasal cavity, MERFISH revealed that every one of the ~1,100 receptor genes has a distinct average position along the tissue’s dorsoventral axis (running from the top of the nasal cavity toward the bottom). Instead of four overlapping zones, the receptors tile the epithelium in organized stripes, each only a fraction of a millimeter wide. Critically, those stripes land in the same place in every mouse examined, making the pattern stereotyped rather than random.
A companion Cell paper, led by Catherine Dulac and Xiaowei Zhuang at Harvard, extended the mapping into the olfactory bulb, the brain’s first relay station for smell signals. That study found that the striped arrangement in the nose is mirrored by matching gradients in the bulb. Sensory neurons projecting from a given stripe in the epithelium connect to a predictable region of the bulb, preserving the spatial code as information travels from nose to brain.
Why the old model lasted so long
The four-zone framework dates to landmark experiments in the early 1990s that used in situ hybridization to localize small numbers of receptor genes. Those studies correctly identified broad dorsal-to-ventral gradients, but the technology of the era could only probe a handful of receptors at a time. With limited sampling, the zones looked diffuse and overlapping, and the field settled on a model in which receptor placement within each zone was essentially random.
Later work nudged the picture forward. A 2018 study in Chemical Senses produced what was then called a near-complete spatial map of mouse olfactory receptors, but it detected only coarse gradients and lacked the resolution to pin individual receptors to specific coordinates. (No DOI or direct link for this study could be confirmed; readers should search Chemical Senses 2018 archives for the original paper.) A 3D transcriptomics atlas published in Nature Communications mapped gene expression across the mouse olfactory mucosa and built a useful anatomical framework, yet it too stopped short of receptor-level precision. The May 2026 MERFISH data resolve what those earlier efforts could not: fine-grained stripes rather than broad, overlapping patches.
Nature’s news coverage of the two Cell papers explicitly frames the result as overturning the textbook model of olfactory receptor organization, an editorial judgment that aligns with the sharp contrast between the old zones and the newly described stripes.
What the studies do not yet answer
The most obvious limitation: this is a mouse map. No equivalent single-receptor-resolution dataset exists for humans. A single-cell and spatial atlas of early human olfactory development, published in Nature Communications, shows that the human olfactory epithelium is spatially patterned during fetal growth, and MRI tractography work has traced topographical connections between the human epithelium and bulb. Both findings are consistent with the idea that spatial order may exist in people, but neither proves that human receptors form the same organized stripes seen in mice. Humans also have far fewer functional olfactory receptor genes (roughly 400 versus the mouse’s ~1,100), so the stripe architecture, if it exists, could look quite different.
Function is another open question. The stripes are reproducible, and the nose-to-bulb projection gradients suggest the brain could, in principle, use positional information to help decode odor identity. Yet neither Cell paper includes direct behavioral experiments testing whether disrupting a specific stripe impairs detection of particular smells. A targeted experiment, for instance engineering mice with shifted receptor expression zones and then measuring selective deficits in odor discrimination, would be a strong next step, but no such data have been published as of June 2026.
Durability over time is also unaddressed. The papers describe the map in healthy adult mice at a single time point. Whether the stripe arrangement shifts with aging, viral infection, or chronic chemical exposure remains unknown. That gap carries real medical weight. Smell loss after respiratory illness, a problem that gained widespread attention during the COVID-19 pandemic, affects millions of people. If certain stripes prove more vulnerable to inflammatory damage or environmental toxins, that could help explain why some odor qualities vanish while others survive after illness or injury.
Finally, the developmental machinery behind the stripes is still murky. Classic work has implicated gradients of transcription factors and guidance molecules in patterning the olfactory epithelium, but tying those molecular gradients to the newly described receptor stripes will require additional experiments. It is similarly unclear whether the positional code is laid down early and stays fixed, or whether activity-dependent refinement during postnatal life sharpens initially broad expression domains into the narrow bands now observed.
What changes for researchers and clinicians
For olfactory neuroscientists, the practical consequence is immediate. Computational models of odor coding that assume random receptor placement within zones will need to be rebuilt with precise positional information. That change could alter predictions about how similar two smells should seem, how easily the brain can untangle complex mixtures, and how robust the system is when particular receptor populations are lost.
For clinicians studying smell disorders, the spatial code introduces a new variable. If receptors in a particular stripe are selectively vulnerable to damage, patients might lose sensitivity to specific classes of odorants in a patterned way rather than across the board. Being able to link a patient’s perceptual complaints to disruption of defined receptor bands could eventually guide more targeted diagnostics or rehabilitation strategies. Those applications remain speculative, but they illustrate why a basic anatomy finding matters well beyond the textbook.
Why the four-zone diagram is ready for retirement
The emerging picture is not that past work was wrong so much as incomplete. Earlier studies correctly identified broad organization and gradients but lacked the tools to see that every receptor has its own address. The new MERFISH atlases show that the olfactory epithelium is not a fuzzy patchwork; it is a finely striped landscape, and the olfactory bulb preserves that layout as signals move into the brain.
How that anatomical precision shapes perception, learning, and disease is the next frontier. Answering those questions will require experiments that connect maps on the microscope slide to behavior in the real world, and, eventually, equivalent maps built from human tissue. Until then, the mouse data alone are enough to retire the four-zone diagram that has anchored olfactory neuroscience since the 1990s.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
