Theta oscillations are an organizational unit of odor processing in the olfactory bulb.

Abstract

When sampling odors, humans typically take a single long sniff, unlike most other mammals who sample odors through bouts of rapid repetitive sniffing. Decades of work has established that rapid sniffing rhythms underlie the organizational principles of odor coding, with sniff speed clocking odor responses in the olfactory bulb. In the absence of rapid sniffing, how are odor responses organized in the human olfactory system? Because most mammals sniff at rates centered around the theta frequency, we hypothesized that the olfactory bulb exploits a theta-range neural oscillation to set the pace of odor coding in the system. Here, we used high-precision neural recordings from the human olfactory bulb to show that initiation of a sniff elicits and temporally aligns theta oscillations in the bulb and that sniff-induced theta oscillations organize the timing and amplitude of odor responses. These findings suggest that, despite the lack of rapid sniffing bouts in humans, the system has preserved a similarly timed unit of olfactory processing.