CHICAGO — Northwestern University researchers published two studies on July 3, 2026, in Science Advances, indicating that rodents and humans use the same neurophysiological rhythm to process smells. Both species rely on similar underlying neurophysiology to detect odors within a single, deliberate sniff.

One study determined that mice inspect food through single sniffs, while the other found that humans organize odor information rapidly within a single sniff. Although a mouse's single sniff is shorter than a human's, the underlying tempo of smell processing is consistent between mice and humans. John M. Barrett, a research assistant professor of neuroscience at Northwestern University Feinberg School of Medicine, described this consistency by stating, "The true similarity is this single sniff, but it's not just a sniff. Mice even move their hands while sniffing, which shows it's volitional - they're doing it on purpose."

The first study, conducted in the lab of Gordon M. G. Shepherd at Northwestern University Feinberg School of Medicine, involved colleagues from the University of Pennsylvania and the University of Florida College of Medicine. The research team constructed a robotic multi-camera recording system to track mice foraging and eating. Mang Gao and John M. Barrett led the tracking of the mice's hand and head movements and breathing. Mice coordinated their hands, head, and breathing to time a single sniff to the exact moment food reached their nose.

Mice engaged in more vigorous sniffing when handling unappetizing food. The presence of odor alone did not prompt their sniffing behavior. Scientists observed that mice continued performing food sniffs even when their sense of smell was interfered with, but silencing the motor cortex stopped the sniffing behavior. "This means when mice sniff food, they're not doing it as a reflexive response to an odor, but rather as a proactive act of deliberate sensory sampling," said Mang Gao, a postdoctoral scholar. Gao added, "It turns out the mice choose to perform these quick 'smell checks,' which is characteristic of a lot of human olfactory behavior, rather than being passively triggered to sniff."

The second study originated from the lab of Christina Zelano in the department of neurology at Feinberg, with collaboration from Dr. Bruce Tan of the department of otolaryngology. Andrew Sheriff, a postdoctoral scholar in Christina Zelano's lab and the first author of the studies, commented on the research objectives, saying, "We wanted to understand how we can identify odors as fast as rodents do even though we sniff over 10 times slower."

The team employed a minimally invasive, high-precision method to record sniffing in the brains of healthy human volunteers. A single intentional inhalation by human participants resulted in low-frequency brain waves, known as theta oscillations (2–8 Hz), in the human olfactory bulb. These theta oscillations occurred at the same frequencies at which rodents sniff. This slow brain rhythm assists in organizing faster bursts of activity that occur during the processing of a smell. Sheriff stated, "By recording directly from the human olfactory bulb using a novel technique, we were able to find rhythms of odor processing that closely resemble those of rodents, suggesting conserved time windows for olfaction across species."

Qiaohan Yang, a graduate student in Northwestern University Interdepartmental Neuroscience, noted these findings. "The implications of our findings are significant," Yang said. Yang observed that in rodents, sniffing and theta are closely unified. "In rodents, sniffing and theta are so tightly fused that the two are nearly indistinguishable," Yang said. "In humans, the slower sniff rate pulls them apart, revealing the theta oscillation as a distinct, independently generated rhythm that a single deliberate inhalation is sufficient to engage," Yang concluded.