Odor coding in awake mice

Olfaction is traditionally considered a ‘slow’ sense, but recent evidence demonstrates that rodents are capable of making extremely difficult odor discriminations rapidly, in as little as a single sniff. To understand the temporal aspects of olfactory information processing, we studied how sniffing shapes the responses of mitral/tufted cells in awake mice. We found that odorants evoked precisely sniff-locked activity in mitral/tufted (M/T) cells in the olfactory bulb of awake mouse. The trial- to-trial response jitter averaged 12 ms, a precision comparable to other sensory systems. Individual cells expressed odor-specific temporal patterns of activity and responses were more tightly time-locked to the sniff phase than to the time after inhalation onset. Precise locking to sniff phase may facilitate ensemble coding by making synchrony relationships across neurons robust to variation in sniff rate. Additional feature that olfactory system should encode is odor intensity. Psychophysical experiments in humans demonstrate that perceived odor intensity falls rapidly with repeated sampling. Changes in perceived intensity can also be due to changes in odor concentration. We show that activity of M/T cells is a neural corelate of psychophysical phenomena.