Many bird species have outstanding spatial abilities as visible during migration, homing or food caching. Just like in mammals, these spatial functions rely heavily on the integrity of the hippocampus (HC). Interestingly, recent studies reporting place cells and sharp wave ripples in birds find physiological differences between dorsomedial and ventrolateral hippocampal regions, suggesting a laminar organization along the transverse axis that seemingly stands in contrast to the non-laminar appearance of the avian HC. Here, we investigated the intrinsic connectivity of the pigeon HC especially with respect to this potential segregation of subdivisions. Using in vivo and high-resolution in vitro tracings, as well as by analyzing the neurochemical profile, we indeed identified two distinct processing streams along the avian hippocampal transverse axis that might have different functional specializations.  Overall, our study suggests that the avian HC contains a complex intrinsic network suitable to sustain and modulate incoming neural activity by a recurrent neural network.

Rook, N., Stacho, M., Schwarz, A., Bingman, V. P., & Güntürkün, O. (2023). Neuronal circuits within the homing pigeon hippocampal formation. Journal of Comparative Neurology, 531(7), 790-813