Investigating map-like navigation and hippocampus homologs in teleost fish: Comment on Givon et al., 2023 "Lateral and medial telencephalic pallium lesions impair spatial memory in goldfish".

This commentary critically examines the article by Givon et al. (2023), which reports that lesions to the lateral or medial regions telencephalic pallium (Dl or Dm) both impair allocentric spatial navigation in goldfish and concludes that both regions are necessary for this function. This interpretation challenges the extensive body of evidence supporting the functional dissociation between Dl and Dm. In particular, Dl's ventral subdivision (Dlv) has been shown to be essential for map-like spatial memory. In contrast, Dm has been associated primarily with emotional and motivational processes rather than spatial cognition. This commentary focuses on the fact that Givon et al's behavioral tasks (a plus-maze and a breadboard maze) lacked essential controls, such as systematic maze rotations and probe trials, that are necessary to rule out non-allocentric behavioral strategies. Moreover, the lesions are poorly localized, including some that extend well beyond the pallium and affect subpallial telencephalic regions and even the mesencephalic optic tectum - structures whose damage produces widespread sensorimotor and regulatory disturbances. Furthermore, the relatively high post-surgical mortality indicates nonspecific surgical effects. Overall, we conclude that Givon et al. (2023) does not provide convincing evidence for a role of Dm in allocentric navigation and does not undermine previous findings of a functional dissociation between Dl and Dm. We briefly discuss how these findings impact the ongoing search for a hippocampus homolog in teleosts and the larger effort to elucidate the neural mechanisms underlying spatial navigation in teleosts.