What happened
- Two researchers, Hathaway and Coleman, published on 6 November 2026 in PNAS a study on how the human brain processes odours in relation to breathing.
- They recorded nasal respiration and brain activity with electroencephalography at the same time in 17 participants.
- They presented naturalistic odours, peppermint, oregano and grapefruit, synchronized to each person’s breathing cycle.
- They found that odour-evoked brain activity is organized by respiratory phase and not by absolute time.
Why it matters
- Smell is fundamental to perception, memory and emotion, but its neural basis in humans is poorly understood.
- Traditional analyses align activity with the moment the stimulus arrives. Because the duration of each breath varies, that method can hide patterns.
- The authors conclude that natural breathing structures the dynamics of the olfactory cortex.
The number
0.79, 0.67 and 0.62. Those are the areas under the curve with which peppermint, oregano and grapefruit could be detected from brain signatures, using leave-one-subject-out validation. A value of 0.5 equals chance, so detection was clear with peppermint and modest with grapefruit.
Context
The responses, called respiratory phase-locked event-related spectral perturbations, appeared in frontal and temporal regions during the first breath after the stimulus. The most discriminative signatures were theta-band activity during inhalation and alpha-band activity during exhalation.
Those patterns were hidden in time-locked analyses, precisely because of the natural variability in the duration of each breath. Since detection worked on people the model had not seen, the phase-locked features generalize across individuals.
To connect neural activity with experience, the authors measured odour recognition with free-response descriptions scored by semantic similarity, without relying on the person naming the odour, something that is impaired in some populations. According to the abstract, behavioural recognition followed the same hierarchy as neural decoding. With 17 people and three odours, the result is a first signal that needs replication.
At Mamífero we follow basic neuroscience. We reported that the brain removes neurons with highly altered genomes around birth and that three neurons suffice to generate the rhythm of a fly’s walk. Also that Qom communities in Argentina lost 35 minutes of sleep in a decade and that lead harms long-term memory by disrupting mitochondrial redox balance.
What’s next
- Replicating the result with more people and more odours would show whether the phase-based organization holds.
- Smell studies could align their analyses with breathing instead of time.
- The authors suggest the approach helps assess smell without depending on the person naming the odour.
Bottom line
The brain does not count odours in seconds, but in breaths. Measured with the wrong clock, part of the signal is lost.
Sources
- Hathaway and Coleman, “Respiratory phase orchestrates human olfactory cortical dynamics”, PNAS, 6 November 2026, DOI 10.1073/pnas.2619920123. This note is based on the paper’s abstract.
- Cover image: Ivar Leidus, CC BY-SA 4.0, via Wikimedia Commons
Edited by Rodrigo Cornejo. How we select and verify: who writes these notes.
