Cell signalling
How does piriform cortex split odor identity from intensity?
Open access · cc by · source: Europe PMC
In 459 piriform neurons from 5 awake mice, which cells fire encodes odor identity, while spike timing—not rate—encodes intensity.
How this study connects
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Study at a glance
- Design
- Animal / in-vitro — Large-scale silicon-probe recordings from anterior piriform cortex (and a subset of olfactory bulb) in awake, head-fixed mice during odor presentation.
- N
- N=5 · Five mice; 459 layer II piriform neurons from nine recordings (33–73 units/recording); 126 mitral cells in 6/9 experiments.
- Population
- Awake head-fixed mice smelling monomolecular odorants at varying concentrations.
- Outcome
- How piriform population spike identity vs timing encodes odor identity and intensity.
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Inspect source passages
How does piriform cortex split odor identity from intensity?
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459 layer II neurons from nine recordings in five mice.
Our dataset contains 459 layer II neurons from nine separate recordings in five mice
23% of cells activated by ≥1 of six odors; 33% suppressed.
23% of cells (105/459 cells) were activated by at least one of the six odors, while 33% of cells (150/459 cells) were suppressed
Key findings
Knowing which neurons were activated was enough for identity; spike count added little. Rate did not track concentration. A fast, concentration-invariant population was followed by later responses whose latencies shortened at higher concentrations. Cortical inhibition sharpened bulb output. Representations were not sparse: ~7% of cells activated and 13% suppressed per odor.
Methodology
Recorded large populations in anterior piriform layer II of awake head-fixed mice (plus some olfactory bulb mitral cells) while presenting odors, then decoded identity vs concentration from spike count, which-neurons-fired, and spike-time codes.
Limitations
Recordings are from head-fixed mice and monomolecular odors; they do not prove how humans perceive intensity, and decoding analyses do not equal a complete circuit mechanism of smell.
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