Odor information is represented by both intensity and timing of neuronal activity in the olfactory bulb, but origins and roles of the temporal pattern remain enigmatic. Here we addressed this issues using two-photon calcium imaging of the mouse olfactory epithelium and olfactory bulb. We found that nasal airflow produces widespread responses in olfactory sensory neurons, and thereby entrains respiration-locked theta oscillations in mitral/tufted cells. Most glomeruli demonstrated the theta oscillations, but their oscillation phases relative to the sniff cycles were glomerulus-specific. Changes in sniff speed or frequency affected activity intensity, but had minor effects on the relative phase. In contrast, odor stimuli generated odor- and glomerulus-specific phase shifts, indicating that phase information distinguishes odor responses from airflow responses. Notably, during odor sampling across multiple sniffs, intensity of odor-evoked activity dynamically evolved over time; however, the phase code remained constant across sniffs. Thus, the phase code can more stably represent odor identity than the rate code. The airflow sensation by OSNs is essential for the phase odor coding, because the phasic representation of an odor was impaired under continuous airflow condition. Furthermore, the airflow-induced theta oscillations were important to increase response sensitivity to an odor. Together, our result demonstrates that glomerular theta oscillations driven by the nasal airflow are the basis for reliable perception of odor information. The phase coding may be a sampling mode-invariant and noise-resistant odor coding strategy.
Position and Honors
- 2007 : GE & Science Prize for Young Life Scientists
- 2009-present : PRESTO researcher, Japan Science and Technology Agency (JST)
- 2010-present : Team Leader, RIKEN Center for Developmental Biology (CDB)
- 2010-present : Visiting Associate Professor, Graduate School of Biostudies, Kyoto University