Decoding olfactory bulb output: A Behavioural assessment of rate, synchrony, and respiratory phase coding

The olfactory system is a well-known model for studying the temporal
encoding of sensory stimuli due to its rhythmic stimulus delivery through
respiration. Sniff-locked activity is pervasive in the primary olfactory
area, the olfactory bulb, and is considered critical to structuring the
output of its computation. We tested the behavioural importance of these
temporal features using simple closed-loop optogenetics embedded in custom
behavioural paradigms. We found that mice perceive differences in evoked
spike counts and discriminate between synchronous vs. asynchronous
activations of the output neurons. Surprisingly, they failed to
distinguish the timing of evoked activity relative to the sniff cycle.
These results suggest that, beyond the first steps of olfactory
processing, sniff rhythms play a more nuanced role, with greater reliance
on the spike rate and synchrony for the neural encoding of the
environment, consistent with gradual transformation of encoding format at
successive stages of sensory processing.