Changes in weak pair-wise correlations during running reshapes network state in the main olfactory bulb

Neural codes for sensory representations are thought to reside in a broader space defined by the patterns of spontaneous activity that occur when stimuli are not being presented. To understand the structure of this spontaneous activity in the olfactory system, we performed high-density recordings of population activity in the main olfactory bulb of awake mice. We found that spontaneous activity patterns of ensembles of mitral and tufted (M/T) cells in the main olfactory bulb changed dramatically during locomotion, including decreases in pairwise correlations between neurons and increases in the entropy of the population. Maximum entropy models of the ensemble activity revealed that pair-wise interactions were better at predicting patterns of activity when the animal was stationary than while running, suggesting that higher order (3rd, 4th order) interactions between neurons shape activity during locomotion. Taken together, we found that locomotion influenced the structure of spontaneous population activity at the earliest stages of olfactory processing, 1 synapse away from the sensory receptors in the nasal epithelium.