Abstract
The human olfactory system has two discrete channels of sensory input, arising from olfactory epithelia housed in the left and right nostrils. Here, we asked whether primary olfactory cortex (piriform cortex, PC) encodes odor information arising from the two nostrils as unified or distinct stimuli. We recorded intracranial EEG signals directly from PC while human subjects participated in an odor identification task where odors were delivered to the left, right, or both nostrils. We analyzed the time-course of odor-identity coding using machine learning approaches, and found that odor inputs from the ipsilateral nostril are encoded ∼480 ms faster than odor inputs from the contralateral nostril. This temporal staggering across the nostrils gave rise to two non-overlapping epochs of odor coding within a single sniff when odors were sampled through both nostrils. These findings reveal that PC maintains distinct representations from each nostril by temporally segregating odor information, highlighting an olfactory coding scheme at the cortical level that can parse odor information across nostrils within a single sniff.