The Olfactory Pathway Preserves Sensory Transmission During Sleep

Decreased responsiveness to sensory stimuli during sleep is thought to be mediated via a thalamic gate. However, olfactory information can gain access to olfactory cortices without an obligatory thalamic relay. It remains unknown how the olfaction system “gates” information flow during sleep. Here we simultaneously recorded local field potentials (LFPs) in hierarchical olfactory regions (olfactory bulb, piriform cortex, and orbitofrontal cortex) while optogenetically activating olfactory sensory neurons, ensuring consistent peripheral inputs across sleep/wake states in freely behaving mice. Surprisingly, evoked LFPs in sleep states (both NREM and REM) were larger in amplitude and contained greater gamma band power than in wakefulness. These findings argue against a central olfactory “gate,” further supported by single unit recordings in the piriform cortex showing nonattenuated information transmission during sleep. Quantitative analysis of nasal breathing revealed slower respiration rates and shallower inhalation slopes during sleep, supporting a peripheral “gate” that physically regulates state-dependent olfactory inputs.