Abstract: Locomotor activity has a substantial influence on incoming sensory input and on the manner by which this input is processed. In the visual modality, locomotion has been shown to increase responses to visual stimuli in the visual cortex. Interestingly, within the auditory modality locomotion has been associated with inhibited spontaneous and sound-evoked responses in pyramidal cells, with the strongest inhibition observed in response to reafferent, self-generated sounds. However, previous studies have focused on the effect of locomotion on the activity of single cells, while the effect of locomotion on local network dynamics in the auditory cortex remains largely unknown. To address this knowledge gap we used two-photon calcium imaging to monitor activity in local neuronal ensembles in the auditory cortex of awake head-fixed Thy1-GCaMP6f mice that were free to stand, walk or run on a treadmill. Using this approach we analyzed single-cell and network response properties of excitatory pyramidal neurons to different sounds under different behavioral states. Our preliminary results demonstrate substantial heterogeneity of locomotion-related modulation of neural activity within local neural ensembles. Neighboring neurons exhibited differential and often divergent influence by locomotion: while some neurons exhibited reduced activity during locomotion as expected, responses of other neurons within the same ensemble were often strongly enhanced. Furthermore, heterogeneity in the effect of locomotion was observed on both spontaneous and sound-evoked responses, and for neural responses to different types of sound stimuli. These results may offer clues to the nature of network-level sound processing that underlie the perception of hearing during locomotion.