摘要Brain systems engage in what are generally considered to be among the most complex forms of information processing. In the present study, we investigated the functional complexity of anuran auditory processing using the approximate entropy (ApEn) protocol for electroencephalogram (EEG) recordings from the forebrain and midbrain while male and female music frogs (Babina daunchina) listened to acoustic stimuli whose biological significance varied. The stimuli used were synthesized white noise (reflecting a novel signal), conspecific male advertisement calls with either high or low sexual attractiveness (relfecting sexual selection) and silence (relfecting a baseline). The results showed that 1) ApEn evoked by conspeciifc calls exceeded ApEn evoked by synthesized white noise in the left mesencephalon indicating this structure plays a critical role in processing acoustic signals with biological signiifcance;2) ApEn in the mesencephalon was significantly higher than for the telencephalon, consistent with the fact that the anuran midbrain contains a large well-organized auditory nucleus (torus semicircularis) while the forebrain does not; 3) for females ApEn in the mesencephalon was signiifcantly different than that of males, suggesting that males and females process biological stimuli related to mate choice differently.