Auditory cortex (ACX) neurons are sensitive to spectro-temporal sound patterns and violations in patterns induced by rare stimuli embedded within streams of sounds. We investigate the auditory cortical representation of repeated presentations of sequences of sounds with standard stimuli (common) with an embedded deviant (rare) stimulus in two conditions – Periodic (Fixed deviant position) or Random (Random deviant position). We used extracellular single-unit and 2-photon Ca2+ imaging recordings in Layer 2/3 neurons of the mouse (mus musculus) ACX of either sex. Population single unit average responses increased over repetitions in the Random-condition and were suppressed or did not change in the Periodic-condition, showing general irregularity preference. A subset of neurons showed the opposite behaviour, indicating regularity preference. Furthermore, pairwise noise-correlations were higher in the Random-condition than in the Periodic-condition, suggesting a role of recurrent connections in the observed di...