Aging shifts brain circuit signals for smell in mice
Brain recordings in awake mice revealed higher excitation, altered electrical rhythms, and less distinct smell signals in the olfactory bulb of older animals.
bioRxiv
In young and old mice, researchers recorded electrical activity from the olfactory bulb and the piriform cortex, two brain areas that process smell, while the animals were awake and exposed to odours.
Both regions in older mice showed a shift toward greater excitation, along with reduced activity of inhibitory neurons, which quiet neural signals, in the piriform cortex. Odour-evoked brain waves also shifted within and between regions, showing strongly elevated rhythms in the beta frequency range. Odour patterns across groups of brain cells became less distinct in the olfactory bulb, but not in the piriform cortex. Analysis of these measures indicated that several partly independent processes reshape smell signals with age, rather than a single shared defect.
Why it matters
A fading sense of smell is among the earliest signs of aging and predicts later cognitive decline. Tracing where these signals falter helps researchers map how aging alters sensory processing across the brain.
Caveats
The study compared age groups in mice rather than tracking animals across their lifespan, and the findings appeared in a preprint that has not yet been peer-reviewed.
The paper
Aging reshapes odor-evoked dynamics in central olfactory circuits
Monell Chemical Senses Center
bioRxiv · 8 Oct 2026 · CC BY-NC · Preprint, not peer-reviewed