The volume of the toad medial amygdala-anterior preoptic complex is sexually dimorphic and seasonally variable.

The anterior part of the preoptic nucleus (APON) in anurans is considered to be a center for mate calling. This locus makes an anatomical complex with the amygdala pars medialis (Am). The nuclear volumes of the Am and APON in the male toad are significantly larger than those in the female. In addition, the nuclear volumes of these loci in the hibernating male are larger than those in the post-breeding animal. These results suggest that the Am-APON complex has an important role in male sexual behavior, and this complex can be activated during the breeding season in the spring.