Auditory cortical event-related potentials to pitch deviances in rats

We recorded epidural event-related potentials (ERPs) from the auditory cortex in anesthetized rats when pitch-deviant tones were presented in a homogeneous series of standard tones (oddball condition). Additionally, deviant tones were presented without standard tones (deviant-alone condition). ERPs to deviant tones in the oddball condition differed significantly from ERPs to standard tones at the latency range of 63-243 ms. On the other hand, ERPs to deviant tones in the deviant-alone condition did not differ from ERPs to standard tones until 196 ms from stimulus onset. The results suggest that oddball stimuli can be neurophysiologically discriminated in anesthetized rats. Furthermore, as the difference between ERPs to deviant tones and those to standard tones at the 63-196 ms latency range could be detected only when standard tones precede deviant tones it shows concordance with mismatch negativity in humans.