Summary: We identify smells almost instantly—often far quicker than we consciously notice. New research from NYU Langone shows that the core work of identifying an odor happens within the first fractions of a second inside the olfactory bulb, not in the cerebral cortex as long assumed.
Using a mechanism the researchers call “temporal filtering,” the brain relies on the very first nerve signals produced during the initial 50 milliseconds of a sniff to recognize an odor while suppressing later, background signals.
Key Facts
- Sniff timing: Mice take very rapid sniffs (roughly 250–500 ms per sniff) while human sniffs are slower (about 1–3 seconds). Despite different sniff durations, the critical odor identification occurs at the start of each sniff.
- Precision optogenetics: The team used a custom circuit‑mapping microscope and optogenetic stimulation to record and selectively manipulate individual neural signals with millisecond resolution.
- AI potential: Temporal filtering—prioritizing early-arriving data and ignoring later noise—could inspire more efficient artificial intelligence systems for processing large sensory datasets.
- Vision parallel: The findings echo vision research showing that substantial preprocessing happens in the retina before signals reach the visual cortex.
Source: NYU Langone
Overview
A study led by researchers at NYU Langone Health demonstrates that mice exploit rapid neural interactions in the olfactory bulb—the brain structure just behind the nose—to distinguish one odor from another. The experiments show that a small subset of nerve signals activated within the first few dozen milliseconds of a sniff carry the essential information that identifies an odor.
Published in Nature Neuroscience on April 14, the work focused on how millions of olfactory sensory neurons in the nose connect to glomeruli (clusters of nerve endings) in the olfactory bulb, which then link to populations of mitral and tufted cells (MTCs). The researchers found that the pattern of glomeruli–MTC activity that appears first in a sniff reliably encodes odor identity across different concentrations. Subsequent activity from other glomeruli is largely suppressed, enabling a stable, concentration‑invariant representation of the odor.
The authors call this rapid computation “temporal filtering.” In practice, it means the olfactory bulb selects and transmits the earliest activated signals while blocking later, potentially confounding inputs. This mechanism helps the animal recognize odors quickly and consistently, even when odor strength or background smells fluctuate.
Lead investigators emphasize that the earliest-activated glomeruli–MTC ensembles represent odor identity robustly, whereas MTCs tied to later-activated glomeruli show strong concentration dependence. Electrophysiological and optogenetic probing revealed a brief excitability window at a sniff’s onset followed by longer odor-evoked inhibition, a timing pattern that supports temporal filtering and signal decorrelation between odors.
Implications
These findings challenge the prevailing view that sensory identification primarily occurs in cortical areas. Instead, the olfactory bulb performs important preprocessing that stabilizes odor identity before the cortex receives the information. The discovery aligns with growing evidence from vision research that peripheral structures like the retina perform significant early-stage computations.
The research also suggests practical applications beyond neuroscience. Artificial intelligence systems that handle sensory or streaming data could adopt temporal filtering strategies—prioritizing the first, most informative moments of input and discarding later noise—to accelerate and improve detection and classification tasks.
Next steps for the research team include mapping how temporal filtering distinguishes between closely related odors—such as different citrus fruits—and how the mechanism generalizes across odor categories like berries or stone fruits.
Methods and tools
The study relied on precision optogenetics to activate or inhibit identified neurons with light pulses and to record neural firing with millisecond accuracy. Study lead investigator Mursel Karadas, PhD, developed the circuit‑mapping microscope used to stimulate and trace individual signals in the olfactory bulb’s superficial layers.
Funding and contributors
This work was supported by National Institutes of Health grants U19NS107464, U19NS112953, and R01DC022320. Other NYU Langone co-investigators include Jonathan Gill and Sebastian Ceballo. Co-senior investigators are Dmitry Rinberg, PhD, and Shy Shoham, PhD.
Key Questions Answered
A: The olfactory bulb can register core odor identity in about 50 ms. Conscious recognition requires additional processing in the cortex and other brain areas, so verbal labeling and full awareness follow after a few hundred milliseconds.
A: Not necessarily in all situations. The study shows the system is optimized to capture the first burst of data. A sharp, quick sniff provides a clear initial window of information; repeated rapid sniffs can refresh that window and help filter out background odors.
A: Yes. Many AI systems struggle with sensory overload. Adopting a temporal filtering strategy—prioritizing early, informative input and suppressing later noise—could speed up processing and improve accuracy for environmental sensors and other applications.
Editorial Notes
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full.
- Additional context was added by staff.
About this olfaction and neuroscience research news
Author: David March ([email protected])
Source: NYU Langone
Contact: David March – NYU Langone
Image: The image is credited to Neuroscience News
Original Research: Open access. Title: “Rapid temporal processing in the olfactory bulb underlies concentration‑invariant odor identification and signal decorrelation” by Mursel Karadas, Jonathan V. Gill, Sebastian Ceballo, Shy Shoham & Dmitry Rinberg. Journal: Nature Neuroscience. DOI: 10.1038/s41593-026-02250-y
Abstract
Rapid temporal processing in the olfactory bulb underlies concentration‑invariant odor identification and signal decorrelation
Sensory systems operating in dynamic environments must filter out irrelevant information to build a stable percept. Animals that depend on smell need to identify odors reliably despite changes in concentration, even though receptor activation is concentration‑dependent. This study used an all‑optical approach in awake mice to map connectivity between odor receptor channels (glomeruli) and mitral and tufted cells (MTCs), while monitoring odor responses. The earliest activated glomeruli and MTCs robustly encoded odor identity across concentrations, whereas later-activated glomeruli were concentration dependent. MTC responsiveness revealed a brief excitability window at a sniff’s onset followed by prolonged odor‑evoked inhibition. These results show that the olfactory bulb implements a rapid temporal filter that stabilizes identity across concentrations and decorrelates responses between odors.