• auditory regularity;
  • change detection;
  • event-related potentials;
  • mismatch negativity;
  • Wistar rats


The human brain can automatically detect changes even in repeated melodic contours of spectrally varying sounds. However, it is unclear whether this ability is specific to humans. We recorded event-related potentials (ERPs) in urethane-anaesthetized Wistar rats presented with rare pairs of tones (‘deviants’) interspersed with frequently repeated ones (‘standards’). The frequency of the tones varied nonsystematically across their pairs so that deviants stood out from standards only in the melodic ordering (ascending or descending) of the tones of a pair. We found that the absolute amplitude of the ERP was significantly higher to deviants than standards between 106 and 136 ms from the onset of the deviance, suggesting that the ability to automatically detect changes in higher-order invariant attributes that emerge from consecutive sounds is not specific to humans.