# EEG aligned to breathing phase tells apart three odors in 17 participants

- Published: 2026-11-07 18:21 UTC
- Section: Life & Health › Neurotechnology
- Tags: respiratory phase, olfactory cortex, odor decoding, EEG olfaction, RPL-ERSP, odor habituation, open-source olfactometer, smell assessment
- URL: https://realtech.media/news/rt-d8b525fd77b5857adffac455_eeg_aligned_to/

**Researchers aligned EEG responses to the breathing cycle and decoded peppermint, oregano and grapefruit across subjects. The approach requires no task from the participant.**

![EEG aligned to breathing phase tells apart three odors in 17 participants](https://realtech.media/media/2026/11/9ad4fe21f2206d40.jpg)
*Chris Hope, Wikimedia Commons, CC BY 2.0*

A team reported in Proceedings of the National Academy of Sciences that odor-evoked brain activity in humans is organized by respiratory phase rather than by absolute time [1]. The researchers recorded nasal respiration and electroencephalography (EEG) simultaneously in 17 participants. Peppermint, oregano and grapefruit odors were delivered synchronized to each person's breathing cycle [1].

## Phase-locked EEG responses

Odor presentation produced distinct respiratory phase-locked event-related spectral perturbations (RPL-ERSPs) in frontal and temporal regions. They appeared during the first breath after stimulus onset [1]. The most discriminative signatures were theta-band activity during inhalation and alpha-band activity during exhalation [1]. According to the authors, these patterns were obscured in traditional time-locked analyses because breath duration varies naturally [1].

Leave-one-subject-out cross-validation gave an AUC of 0.78 for peppermint, 0.68 for oregano and 0.61 for grapefruit. The authors conclude that phase-locked features generalize across individuals [1].

## Perception and habituation

To link the neural signals to perception without requiring participants to name the odor, the team collected free-response descriptions and scored them with a semantic-similarity approach. Recognition strength across the odors paralleled the neural decoding hierarchy [1].

Decoding performance declined over repeated presentations, which the authors attribute to selective degradation of the most informative phase-locked features [1]. They describe RPL-ERSPs as a sensitive, task-free approach to assessing olfactory function [1].

The authors also provide an open-source, respiration-synchronized olfactometer design costing under $500, intended to enable replication of the method.

## Sources

1. [Proceedings of the National Academy of Sciences](https://doi.org/10.1073/pnas.2619920123)

---

Source: RealTech, realtech.media — https://realtech.media/news/rt-d8b525fd77b5857adffac455_eeg_aligned_to/