“Limbic associative” and “autonomic” amygdala in teleosts: A review of the evidence

The amygdaloid nuclei form an important hub of structures associated with diverse aspects of cognition and emotional behavior. Homologous structures have been determined in tetrapods, but homology of amygdala-like regions in bony fishes is presently unclear. Based on connectivity patterns, genoarchitecture, chemical neuroanatomy, and functional studies, we suggest that the dorsomedial portion of the pallium of Actinopterygii is the homolog of the basolateral/lateral amygdala (“frontotemporal amygdaloid system”), while the supracommissural and postcommissural portions of the subpallium are homologous to the extended central amygdala (central amygdaloid nucleus and bed nucleus of the stria terminalis). Nonetheless, the differentiation between these nuclei is not as clear-cut as in mammals, and there is no clear evidence for the existence of an “olfactory” medial amygdala in Actinopterygii, suggesting that the parcellation of one or two amygdaloid nuclei into many subnuclei occurred with the appearance of a true vomeronasal system.

► The amygdala of mammals is comprised of several subnuclei, but only one has been tentatively identified in teleost fish. ► The teleostean dorsomedial pallium is the best candidate for the lateral/basolateral amygdala. ► The supracommissural and postcommissural subpallia are the best candidates for the extended central amygdala. ► These subpallial regions also present some markers of the medial amygdala. ► The parcelation of central and medial amygdala occurred with the appearance of a true vomeronasal system.